New Approaches for Regeneration of an Outstanding Baroque Living Heritage, the Széchenyi Linden Allée in Hungary

Abstract

Allées used to be the essential artistic tools and indispensable parts of the strictly architectural, formal Baroque gardens. Beyond the practical purposes of edging paths and garden ways for walking, hunting, or horse and carriage riding, allées played a vital role in marking visual and landscape connections and thus the spatial projection of the noble estate, its wealth, and social rank. In Historical Hungary, Baroque architecture and garden art appeared in German-Austrian and French examples in the 18th century. The Széchenyi Linden Allée is an outstanding linear garden space of Baroque Garden art at Nagycenk, West Hungary. The generous composition, created by the prominent Count Széchenyi family in the mid-18th century, has remained a magnificent entity in the landscape ever since. Despite barely two hundred years of detected or unknown environmental or habitat changes, as early as 1942, the allée received a nature conservation nomination. More than a half-century later, in 2002, the allée became a historical and landscape aesthetical heritage within the Fertő-Hanság Cultural Landscape World Heritage site. Unfortunately, the once magnificent tree lines have severely eroded in recent decades due to mature trees’ subsequent death, inadequate replacement, lack of regular maintenance and tree care, and effects of climate change. In recent years (2011, 2018), landscape and horticultural analyses and visual and instrumental tree assessments were performed to help the conservation and rebirth of the allée, maintain the mature trees, and restore the landscape within a long-term renewal plan. Along with the 2018 survey and plan, the short-term maintenance works were completed in 2019–2020. This study, based on site surveys in 2022 and 2024, aims to identify the results of the primary management, analyses the vitality of mature trees after crown reductions, and then proposes a resilient and sustainable regeneration method with the habitat, cultural, natural, and genetic heritage, and the feasible maintenance contexts in focus. As proposed in the 2018 plan, the reproduction of mature trees started in 2020 and resulted in well-developing grafts for a later allée restoration. Due to the challenges of climate change, the regeneration project requires a special, long-term restoration management plan with a special focus on the still vital and possible remaining mature trees, the well-growing individuals from previous replanting, and the nursery school seedlings conserving the genetic heritage of the Széchenyi lime trees with long-viability capacity.

1. Introduction—Allées in Garden Art and Landscape Architecture

In the history of garden art, since ancient times, we can find numerous examples of tree allées as linear compositions delimiting space, helping orientation and travel, indicating the rank of the estate, or for compositional and decorative purposes [1,2]. The allée became of great importance as an artistic and dynamic space form in the Baroque era: they appeared in the garden, in the bosques and hunting woods, and over the estate centre in the open landscape, signifying wealth, power, and ruling the whole property system [3]. Allées often designate the appearance of the architectural ensemble as a generous composition and a large-scale spatial organization. All over Europe, centuries-old allées from the late Baroque period are still witnessing the princely garden and landscape creations of long-gone times. The famous garden designers of the 17–18th century (A. Le-Notre, F. L. Sckell, etc.) connected the Baroque garden ensembles into the landscape within the estate and, even further, with linear garden elements [4]. Due to the vitality and respectable size, the individual trees and the entire allées represent a remarkable cultural, landscape architectural, and horticultural value. These mature linear landscape elements within gardens and landscapes need special methods for conservation or renewal. Furthermore, the trees standing for centuries in the allées prove a long life capacity and good tolerance, so their gene set also should be conserved as natural genetic heritage.

1.1. Formal and Taxonomical Aspects of Baroque Allées

The most common form is a double row of trees with a walkway or greenway (allé vert) in the middle. The 2 × 2 row installation embodies a monumental space creation like the Grand Avenue at the Blenheim Estate, Oxfordshire [5], or the once famous Baroque landscape element, the Esterházy linden allée in Köpcsény (now Kittsee, Austria) that created a grandiose visual connection to the Pozsony (Pressburg/Bratislava) castle hill [6]. In some cases, three rows of trees create a double pathway system like the bordering allées along the main parter in the Esterházy garden at Fertőd-Eszterháza (Figure 1) [7,8].

According to the plantation, trees of Baroque allées came from the main stand—forming species of European forests that grow strong canopy and can tolerate pruning. Typical allée tree species from the natural flora were elm trees, beech, and oak trees, hornbeam, or linden trees (Ulmus, Fagus, Quercus, Carpinus, or Tilia) [5]. In Hungary, this meant the extensive use of the so-called precursor species, the linden trees (Tilia cordata, Tilia platyphyllos), because of their longevity and respectable size in solitaire, serial, or loose position [9]. Allées in Baroque gardens formed a trimmed, architectonic space wall (such as vue in Schönbrunn, Vienna), at least in the garden spaces; however, the artificially pruned allée in the open landscape is questionable, at least the wide planting distance refers to this [10]. On the other hand, if there was pruning, it mostly served the basic crown shaping and strengthening of the young trees. Besides the native linden trees, the white horse chestnut (Aesculus hippocastanum) originating on the Balkan peninsula also appeared in the 18th century’s allées [10]. The tree selection of allées was obviously moderate to fit this linear garden element into the designed strict architectural garden forms.

1.2. Conservation and Reconstruction of the Living Heritage of Allées

The reconstruction of “surviving” Baroque allées is a serious challenge, even if the restoration of the trimmed space walls—with a few exceptions—rarely occurs nowadays. Furthermore, 250–300 year old allées of mature trees are very rare in Europe; in most cases, the trees had to be replanted at least in the 20th century, if not earlier, within an overall garden reconstruction program. In the Schönbrunn Baroque garden, the regular pruning of the green walls enclosing the great parterres belongs to the continuous maintenance tasks; still, the green space walls needed a sizeable cut-back and a replantation intervention to recreate the space proportions of the statues along the parterre. By the late 20th century, the statues along the parterres have been swollen by the continuously growing green wall. The management debated the restoration methods and ways, either the statues should have been moved ahead, or the green walls’ trees needed a valuable cut back and occasional replanting. Taking the authentic space proportions into consideration, the green wall renewal seemed the plausible and long-term-relevant intervention even if the overall sight of the trees would recover in several decades (Figure 2) [11].

Schlosshof, the once hunting lodge and one of the imperial estates of Austria, represents the full reconstruction of a high Baroque garden ensemble, where many space-forming and framing allées were renewed either in trimmed or naturally growing form. The once royal ensemble (designed by Lucas von Hildebrandt and Anton Zinner; Schmidt 1993) shines in its old glory thanks to the 2003 reconstruction project [12].

In the Hungarian Fertőd-Eszterháza, the triple-rowed allées framing the main parterre formed a strict architectural character both in the Baroque era and later, in the early 20th century eclectic times, when the garden renewal aimed the reconstruction of the original features. Unfortunately, due to the lack of further regular, professional treatment and wounds caused by previous pruning, the linden and horse chestnut trees died faster than expected. Crown pruning and trimming seems like a questionable maintenance method nowadays from ecological and ethical aspects.

Baroque allées still live in the tree canopy and need special maintenance and renewal methods. Regular tree care is the primary maintenance to keep up the allée’s healthy conditions and decorative value as long as possible; on the other hand, in the case of mature trees, rejuvenation may help to extend the allée’s life expectancy. The Hungarian High-Baroque Garden heritage at Fertőd-Eszterháza is famous for a set of large-scale allées that had both replanting and rejuvenation to support the long-term preservation. The early 21st century garden reconstruction program aimed the rejuvenation of mature trees [13]. Besides the best maintenance, as time goes by, trees may be felled, for example, due to storm damage, and leave the allée incomplete or punctured; replantation with the same taxon and expediently with full-grown trees is the traditional allée management method to recreate the homogeneous character within a short time. The Grand Avenue at Blenheim was planted on Vanbrough’s plan in 1716 with 686 large elm trees (Ulmus minor syn. Ulmus campestris) in two double rows [5]. During two centuries, the elm tree allée needed only several, one-by-one, or short intermittent replantations with the original taxon and full-grown trees [5].

A full replantation or renewal would be necessary if the allée trees die in large quantities due to disease or pest attack. The Blenheim Grand Avenue is a good example of such a necessary renewal. The Blenheim Palace in Oxfordshire, UK has been a World Heritage Site since 1987 [5]. It is one of the finest princely palaces in the world, built to honour General John Churchill, the first Duke of Marlborough. The 2.3 km-long Grand Avenue is planted in 2 × 2 rows with elm trees, and the Column of Victory commemorates the victorious battle of Blenheim. The time for the first replantation came in the late 19th century when the allée showed a poor condition with a “series of discontinuous blocks”. The taxon-authentically reconstructed elm tree allée, though on a slightly different pattern around the columns, started to flourish in 1902. Unfortunately, six decades later, the elm tree disease (Ophiostoma novo-ulmi), a fungal infection introduced from America, reared its head and had seriously damaged the allée; by the late 1970s, the Grand Avenue required a total replantation and the introduction of a new taxon, the small-leaved lime tree [5]. Both allée replantations tried to preserve the original proportions and artistic requirements despite the different taxon characters.

A similar, duplicated reconstruction confirms that unforeseen ecological problems may be decisive on living heritage. The horse chestnut allée in the Gödöllő Royal Castle garden represents a late Baroque garden art that, due to its essential functional, bordering role, could stay intact when the garden reconstruction aimed a stylistic renewal, the recreation of the formal garden to a landscape garden-type garden in the early 19th century. The horse chestnut allée, with its ≈400 m long line, would have been too rigid an element in the landscape garden thus, a dense tree canopy and bushy plantation corrected the visual appearance and softened the strong architectonic character. After two centuries, in the early 21st century, the allée reconstruction became inevitable due to the poor condition of trees. Within the royal garden’s reconstruction plan, the allée restoration played a dominant role in re-creating the homogenous appearance and the vivid character of the horse chestnut allée. Unfortunately, the Aesculus hippocastanum trees are often attacked by a very common moth infection; the horse chestnut leaf-miner moth (Cameraria ohridella) has spread throughout Hungary by the late 20th century, which is a monophagous species so it can cause severe damage on Aesculus hippocastanum tree stock [14]. Therefore, the allée restoration plan proposed a similar taxon, the Aesculus × carnea ‘Briotii’, that the smaller, compact crown form and the beautiful pink floral scents could fit well into the original plantation rhythm and add an extra decoration along the allée. Unfortunately, a new infection, the bacterial infection of Pseudomonas syringae var. aesculi arrived with the trees imported from abroad, causing decay two years later [15]. Despite the immediate intervention and medical treatment, the trees’ died out rapidly. In 2014, the management decided to fell all of the horse chestnut trees in the allée and total renewal with a new species, the Tilia × europaea ‘Pallida’ trees to block the further spread of the bacterial disease with the infection of the rich Aesculus stock both in the garden and over it in the region.

In addition to the aesthetical, historical, and cultural aspects, there are of course economic and sustainability issues involved in allées’ regeneration. Unfortunately, in many cases, maintenance realities and difficulties either do not allow or only partially support a high-quality, short-term allée reconstruction, even if the authentic character and the uniform appearance would add an extremely strong value to the monument preservation program.

2. Hungarian Baroque Allée Heritage and the Széchenyi Linden Allée

The Baroque garden art in Hungary, influenced by German and French examples and with delayed development due to a 150 year long Turkish occupation, could flourish only from the mid-18th century. Within this relatively short period—compared to the Italian, French, and German Baroque era—the Hungarian high nobilities created valuable palaces, castles, and estates with large-scale gardens and landscapes primarily in the west and north-west regions in the vicinity of Vienna (Bécs, Wien), the centre of the Habsburg Monarchy and Pozsony (Bratislava/Pressburg) and the venue of the feudal assembly considered the predecessor of the parliament [8]. Like the high-Baroque European estates, Hungarian garden art became famous for unique, grandiose creations where tree allées framed the garden spaces and ruled the garden and the neighbouring landscape. [16] Most of these monumental garden and landscape compositions disappeared in the following centuries due to social, stylistic, political, or urban and landscape development changes. Hence, Hungary has a moderate garden art heritage from the Baroque epoch. Besides the Süttör-Eszterháza (called the Hungarian Versailles in 18th c.), castle gardens and landscape are especially rich in various garden and hunting park allées. Still the nearby noble residence at Nagycenk developed a unique landscape-scale allée.

The noble history of Nagycenk (Cenk/Kiscenk at that time) started in the late Baroque period of Hungary due to General Count Antal Széchenyi (1714–1764), who started the construction of the castle in 1741; then, in the 1750′s, as a functional addition and a visual continuation of the Baroque Garden with parterres, a grandiose allée was created running to north, over the country road. The 2.3 km long and 22 m (12 fathoms) wide riding trail had around 600 lime trees along the two sides and terminated in a small hermitage on the plateau looking on the Fertő lake (Figure 3a). The nephew, Count Széchenyi Ferenc (1754–1820), a highly appreciated personality in Hungarian cultural history, was the founder of the National Library and the Museum, inherited the estate, and started the development and the garden reconstruction in English landscape style. Though an enlightened person and a true admirer of English landscape art, Count Ferenc insisted on an allée that opened to a grand view of the Fertő lake, and he even topped the eyecatcher and the termination place with a small chapel (Figure 3b). The next inheritor, his son, Count István (1791–1860) played a determining role in the industrial, agricultural modernisation, and economic and urban development in Hungary, and it was he who transformed the family estate into modern farmland. While maintaining the old allée, he added new allées to the estate to improve the connections within his agricultural fields (Figure 3c). In 1876, the railway line connecting Győr and Sopron cut the allée into two parts. The unity of the Baroque allée, a carefully maintained and cherished heritage of generations, was thus severely compromised from a functional point of view and the vue was also damaged due to the slight ground elevation needed for the railway line stabilization. The fourth-generation heir at Cenk was Count Széchenyi Béla (1837–1918), an honorary member of Hungarian Academy, a traveller, and botaniser who turned the castle garden into a grandiose collection garden and placed her early passed wife’s memorial in the allée grove.

The two centuries long high respect and quality maintenance by the Széchenyi family was over after the 2nd WW and the subsequent nationalisation. The Széchenyi estate, severely damaged in the war, went into state ownership. The castle and its garden opened the gates for tourism after decades of reconstruction, while the linden allée maintenance went into the Sopron University of Forestry’s hand. As one of the earliest nature conservation sites of Hungary, the allée served as an open greenway for the residents and tourists though. Unfortunately, the longer section over the railway line illegally served the local agricultural transport. Professional and regular maintenance jobs were missed out on, and no long-term conservation project was planned for the necessary reconstruction work for the mature trees and allée. Unfortunately, in the absence of professional maintenance and tree care, the allée became incomplete and almost forest edge like. Still, the allée remained one of the most valuable living heritages of the Baroque era in Hungary. After the earlier forest-like management and nature conservation works, a new, complex renewal program was needed to prepare the allée restoration and the greenway renewal within a landscape architecture framework (Figure 4).

Gardens and landscapes are unique, living creatures embedded into an ecological system. On the other hand, their space structure and land use reflect the compositional aim and form of given historical periods. Therefore, gardens are to be considered as a monument: “The historic garden is an architectural composition whose constituents are primarily vegetal and therefore living, which means that they are perishable and renewable”. defines the Florence Charter (Florence Charter 1982. Art. 1. 2) [17]. Historic gardens can be small gardens and open landscapes, independently their formal or landscape character or their scale. As proposed in the Burra Charter (Burra Charter 1979) [18], not only gardens but all sorts of green areas and parks may have historic significance. In this context, an allée should also be considered a historic garden or historic allée within a historic garden as it is an elementary space-forming element or within the broad landscape as part of the estate’s large-scale composition. In the case of landscape-scaled historic allées, the architectural composition with strict proportions and spacing clearly indicates the creative spirit and the will to leave a mark in the landscape. Historic gardens and historic allées have strong cultural significance based on their aesthetic, historical, scientific, or societal values. (Burra Charter 1, 1.2) [18].

The Nagycenk or Széchenyi lime tree allée is a unique Baroque landscape creation of Count Széchenyi’s family, treasured and beloved for generations. The double tree line is a cultural–historical value and living heritage, which represents the memory of an outstanding Hungarian noble family that had a great influence on the rebirth and strengthening of national consciousness and the progression of cultural, scientific, economic, and landscape for beautifying in Hungary. The national and cultural commitment of the Széchenyis played a determining role in 1942 when the Nagycenk allée received legal nature protection as the 7th nature conservation area of Hungary [19]. It is also part of the Fertő Hanság World Heritage Site as a cultural landscape and a listed national treasure. Its cultural significance is unique in many ways.

3. Research Method of Horticultural and Landscape Architectural Surveys of the Nagycenk Baroque Linden Allée

The preservation of the outstanding Hungarian baroque garden art was first outlined in a nature conservation management plan based on a 2001 visual condition assessment. Of the planning proposals, essentially only the most urgent conservation works were carried out. In 2011, a detailed visual condition survey and landscape architecture study was carried out in disciplinary research of the Department for Garden and Open Space Design, Corvinus University of Budapest, drawing attention to the condition of the allée in need of urgent intervention. In 2018, the new heritage management, the Eszterháza Cultural, Research, Festival and Conference Centre (EKKFK), took up the issue of the allée and commissioned the experts who worked out the 2011 survey [20]. In 2018, the expert team worked out the detailed visual and instrumental tree inspection and the landscape architecture survey of the entire linear green space. The reconstruction concept plan was accepted by the EKKFK management, and the short-term was completed in the following years [21]. In 2019–2020, the tree maintenance and the restoration of the greenway habitat went off successfully. Tree maintenance covered the removal or fell of accident-prone trees and injured or infected parts of old trees, while the greenway needed the cut of the thick sprout rings around the trunks, the fell of invasive trees and bushes under the tree canopy, and the cleaning of the lawn level full of weeds, tall grasses, and invasive perennial species. Thanks to the habitat maintenance, the trees were able to breathe again, and the allée regained its openness instead of the forest edge character. The voluntary professional research and surveys carried out by the team of the present publication in 2022 and 2024 aimed primarily at the evaluation of the vitality and improvement of trees and the effects of the accelerating climate change.

Table 1. Overview of allée surveys in 2011, 2018, 2022, and 2024 in Nagycenk (The “x” means the year in which the different aspects of the survey were assessed).

Purpose, Scope and Type of Survey	Years of Surveys
	2011	2018	2022	2024
Interdisciplinary university research	x
Revision of plantation order	x
Dendrological–horticultural tree analyses along the allée	x	x
Individual visual examinations and evaluations		x
Simplified visual inspection	x		x	x
Instrumental examination of old and ancient trees (Fakopp 3D)		x
Targeted analyses of old and ancient trees within the allée				x
Selection of trees of valuable genetic heritage (designation of healthy, old or ancient individuals)		x	x	x
Designation for reproduction in terms of genetic heritage		x	x
Landscape and garden survey of the entire greenway	x	x
Treatment and greenway management plan & recommendations for short term	x	x
Proposals for individual or sectional replantation or for the complete allée renewal in short, medium and long term		x	x
Landscape and garden restoration and development plan		x
Proposals for resilient reconstruction of the allée and the conservation of valiable, vital trees and their genetic heritage				x

shows the aims and methods of the surveys.

3.1. A Comparative Analysis of Tree Surveys’ Results of 2011 and 2018

In general, the quality and vitality of the trees deteriorated significantly in the allée between 2011 and 2018 due to the lack of maintenance, habitat degradation, and severe meteorologic events like heavy storms, decreasing levels of precipitation, and other symptoms of climate change (

Table 2. Comparison of the main results of the 2011 and 2018 allée surveys in Nagycenk.

2011 Survey:	2018 Survey:
581 original plantation sites 610 trees surveyed 327 old, living trees 193 young trees in intermediate sites 78 old trees in excellent health. 167 trees almost dead or dead	505 numbered trees, 278 old trees 35 trees with severe hollows in trunk or crown 27 old trees in excellent health 57 trees dead in 7 years

).

As shown in Table 1, the two surveys were different in their aims and methods. In 2011, the research team (Kinga Szilágyi and Krisztina Szabó team leaders) differentiated the old trees in the original plantation rhythm, and the young ones were planted by the forestry firm responsible for maintenance in 1970–1990. Unfortunately, the new plantation in intermediate positions was far from the authentic rhythm and the favourable habitat for light-loving lime tree species.

We measured 327 old but still living linden trees, most of them remnants of the first planting period or early replantation actions; therefore, these trees could be around 200–250 years old at that time (Figure 5). As a result of previous replanting attempts, 193 young trees lived in an intermediate planting position in 2011, that resulted in weak conditions. Summarising the survey data, about 60% of the original 18th century genetic heritage was still alive and offered reasonable potential for a gene-authentic renewal. The research concluded that previous resettlement and restoration actions had disrupted (non-original spacing and rhythm) the original deployment sequence. Unfortunately, 29% of the trees were in severely degraded stadiums, awaiting an urgent maintenance and reconstruction program.

The official allée survey on behalf of the EKKFK ran in the spring and early summer period of 2018, with a detailed condition survey including visual and instrumental inspections of the trees and a landscape survey of the allée, the greenway, and its surrounding landscape (Figure 6). The assessment of the overall tree condition, with special attention on the trunk and crown form, damages, stability, and strength, went on in the spring season before foliage development, while the vitality assessment and the instrumental measurement of mature and old trees were carried out in the summer period. The result of the instrumental examination is shown in Figure 6d, which is a technical drawing of an instrumental trunk survey based on measuring the sound wave propagation speed between sensors placed on the trunk. The 3D trunk cross-section can show the hidden statically problems (where the blue colour represents the hollow part, the red indicates decay, and the shades of green show the healthy wood parts.). The instrument is a Hungarian development called FAKOPP 3D (Tree-knocker 3D). In 2018, the allée consisted of a total of 505 trees, of which 145 could be from the original or an early replacement. These old trees are essential when thinking about the reconstruction as they may represent a unique genetic heritage. The allée survey ended with a reconstruction-type concept plan for short and medium periods of about 10 years.

The first phase involved the detailed professional horticultural tree care for the whole allée with the definition of 13 treatment categories based on the detailed database and tree inventory (

Table 3. Széchenyi’s Linden tree typology in 2018—categories of care, treatment, and ages.

Tree Typology/Based on Age and Tree Care and Maintenance	Individuals	%	Ages
1. mature trees in good condition, requiring minor treatment; mainly in the crown	9	2	old, mature trees
2. mature trees in good condition, with a slightly damaged branch system: pruning, wound treatment, crown adjustment;	7	1
3. old trees with severely damaged crowns: crown pruning, scar treatment;	13	3
4. old trees with severely decayed trunks and branches: severe crown pruning, wound treatment;	152	30
5. old trees with severely decayed trunks and branches: crown pruning with static reinforcement;	6	1
6. mature tree surviving in suckers: can be retained in the medium term by selection and cleaning of crowns, branches and branchlets;	50	10
7. decayed, severely damaged or deformed trees with or without crowns: removal, stump drilling	22	4
8. middle-aged trees with good crowns in good condition from the first replacement: need little treatment;	41	8	middle aged trees
9. medium-aged trees in good condition with damaged branch system: pruning, wound treatment, crown adjustment;	50	10
10. middle-aged, heavily damaged trees: removal, stump grinding, soil levelling;	8	2
11. young trees in good condition, planted in suitable location: require little treatment;	115	23	young trees
12. crown formation of young trees in good condition, planted in suitable locations;	22	4
13. young tree planted in the right place: damaged, misshapen, to be felled.	8	2
Total	503	100

). The landscape architectural concept proposed a short-term program for the reconstruction of the greenway and its surroundings with a special reconstructive grass layer maintenance to clean out the invasive plants and rehabilitate the whole habitat. The coordinated, complex protection and management plan for nature conservation and landscape protection proposed the development of legal protection within the World Heritage Management Plan. Besides the cultural and touristic development ideas (to maintain a safe, usable, and heritage-relevant greenway and allée character), the plan stressed the genetic heritage incarnated in the many mature trees and the production of authentic propagating sapling material for the further allée renewal.

Our recommendations based on the 2018 surveys were: careful, professional tree care, and greenway management for tourism; sectional reconstruction in the short, medium, and long term; retention of witness trees—1–2 mature trees per section; replanting with young trees propagated from the original genetic stock.

Genetic studies [22] have shown that the species in the tree population have high genetic diversity but differ significantly from the neighbouring region’s lime tree population. The genetic diversity of small-leaved linden (Tilia cordata) was investigated using microsatellite markers. The result is that the Nagycenk small-leaved linden stock is a unique one in a larger region. We assume that the propagation out of stem cuttings of ancient trees was successful, the small trees developed well, which in time would make excellent nursery trees for the allée restoration either in short or longer sections (Figure 7). Unfortunately, the professional nursery treatment has not started yet.

3.2. The First Tree Conservation and Greenway Management Project 2019–2020

Due to the detailed conservation program accepted in 2018, most of the management and maintenance tasks planned for the short term have been completed by early 2020 (Figure 8). The professional care of the trees in the allée and the quality maintenance of the allée’s greenway helps to extend the sustainability of the Széchenyis’ living heritage probably for 10–15 years. However, to protect and improve the tree species habitat, the management of the grassland, and control invasive species and weed communities require ongoing maintenance.

4. Results

Revision of allée management project—Results of site surveys and tree analyses.

The 2019–2020 years’ short-term heritage protection program could focus on the greenway and tree management that resulted in a spectacular improvement of the allée. Unfortunately, Eszterháza Centre (EKKFK) missed the implementation of other issues of the management plan, like legislative issues to strengthen heritage protection, land use regulation rules against habitat damages caused by heavy agricultural vehicles, and landscape design projects to improve the entrance and terminating zones. By 2022, due to the restricted budget, greenway maintenance will lose its priority too.

The essential aim of the 2018 allée renewal concept was the preservation of the historic living heritage, with its cultural, landscape architectural, and ecological values. Maintaining the vital old tries and the younger ones of earlier replantation projects may provide an allée character for the medium and hopefully for the long-term period. Besides the garden and landscape design values, the plan proposed the preservation of the genetic stock incarnated in the originally planted trees, namely in the Tilia cordata trees from the mid-18th century. The number of these methuselah trees has rapidly decreased in the past decades; therefore, it was urgent to start a propagation program. The seeds collected from several ancient trees in the Fall of 2019 have not germinated. Attempts with cuttings taken from fresh shoots were similarly unsuccessful. However, the grafts have taken root, and today, nearly a thousand graft young saplings are waiting for professional nursery maintenance and then the restorative plantation of the historical allée.

Though Eszterháza Centre, the responsible management firm, could not finance the ongoing allée revisions, our research team volunteered in repeated site analyses in 2022 and 2024. With a special focus on the vitality and life expectancy of the allée trees, the site surveys verified the necessity of the professional, although rough and dramatic tree fell, cut back, and rejuvenation. Since lime trees prefer open canopy, not only the many old trees but middle-aged and young, deeply oppressed ones in the trapped state, and even stem-originated trees could utilise the re-opened, loosened tree canopy and the improvement of the grass layer along the greenway. The site analyses resulted in a revised tree typology with vitality and sustainability in focus, which are fundamental in maintaining the allée until the reconstruction is started, hopefully not later than 10–15 years.

4.1. Revised Tree Typology Based on 2022 and 2024 Site Analyses

The revision of the allée and the tree stock asked for a new categorisation due to the results of the tree management plan and the decreased number of trees still standing. The new site analyses focused on the state and vitality of tree canopy, regarding the expected sustainability until the reconstruction of the allée. The simplified tree categories focus mainly on sustainability, regardless of tree individuals’ age: (1). trees that can remain in the short term (3–5 years); (2). trees that may remain in the medium or medium-long term (6–15 years); (3). trees recommended for felling; (4). missing trees that have died since 2018 due to natural death, storm damage, or planned felling (

Table 4. Simplified categories with vitality and sustainability in focus.

No.	States of Vitality and Sustainability	Explanation	2022		2024
			Old, Medium-Aged	Young	Old, Medium- Aged	Young
1	s+	trees that can remain in the short term (3–5 years) as they could pose danger to visitors	100	16	82	5
2	+	trees until medium or medium-long term (6–15 years), even longer in case of young individuals	208	116	218	129
3	−	trees recommended for further felling	30	1	36	3
4	0	missing trees died since 2018 (or since 2022 in case of revision 2024)	22	10	5	1

, Figure 9). With the simplified category system, the sustainability of the allée and the short, medium, and long-term important tree line protection and maintenance tasks are outlined.

4.1.1. Trees Relevant for Short-Term (s+)

Based on our site survey in 2022 and 2024, the old trees that may stay only in the short term (1–5 years) are those that have little decorative value, and barely have a good canopy or the remaining crown parts are drying heavily. This category is relevant for trees with large hollows or open rotten trunks therefore they are more likely to break and thus pose danger to visitors walking along the allée. In a maximum of 5 years period these ‘s+’ trees should be investigated to decide whether they could still stay, though they could hardly avoid felling, due to the severely dying crown or the instable tree structure.

4.1.2. Trees Relevant for a Medium/Long-Term Stay and Maintenance (+)

Trees offered for remaining in the medium (5–10 years) or long (10–15 years) term show high decorative values. Of course, there are many young trees in this category, but also old or middle-aged individuals that have regenerated well after the 2019–2020 tree management program and greenway maintenance. Thanks to the crown cuts, many vital trees developed compact, stabile crowns. We have also listed here those individuals whose trunks are thin and rotten, but thanks to pruning, they are not dangerous anymore. Within a 5 year period, these trees also need revision. Compared to the results of 2022, many young and old trees showed significant improvement in 2024.

The number of missing trees (0) did not change in these two years, though, unfortunately, trees recommended for felling (−) increased slightly (from 31 to 37 trees). In this aspect, the low level of maintenance seems a challenging factor besides the long summer heat periods and the decreasing amount of precipitation (Figure 10).

4.2. Tree Heritage/Heritage Trees

“The historic garden is an architectural composition whose constituents are primarily vegetal and therefore living, which means that they are perishable and renewable” says the Florence Charter, the constitution of ICOMOS-IFLA International Committee for Historic Gardens [17]. The charter, accepted in 1981, aimed to define the historic garden as a special type of historical heritage and monuments and proposed specific rules for the preservation focusing on the time context that is essential in the case of the living “building material” of gardens. Since the appearance of the charter, our world has changed dramatically due to a speeding alteration tendencies of world ecology and the overall climate system. Unfortunately, the living heritage of pieces of garden art and landscape design inevitable face severe challenges caused by degrading ecosystems. Nowadays, we have to think about the relevance of statements like: “Thus its appearance reflects the perpetual balance between the … growth and decay of nature and the desire of the artist and craftsman to keep it permanently unchanged” [17]. Not debating the idealistic wish of garden creators to sustain their creation, it is clearly visible that the 21st century requires greater flexibility and variety in garden maintenance and monument preservation, independently from the historical style. On the other hand, the charter laid a stress on the preservation of historical gardens’ plant heritage as saying: “Care should also be taken to ensure that there is regular propagation of the plant varieties necessary for maintenance or restoration” [17]. It is true, there is no specific mention here of the plant stock constituting the genetic heritage though in the case of trees and tree canopy maintenance and plant propagation have special responsibility due to the time context. In all heritage gardens, independently from the type of design and space forming, from being architectural or landscape characteristic gardens, the tree stock in all tree plantation forms talk about time, about centuries-long history, and about surviving in all circumstances. Methuselah trees reflect and symbolize vitality and strength. When deciding about tree felling in a historical garden, not only the garden character or the space form and proportion changes but hundreds year old genetic heritage might disappear. It is perhaps not an exaggeration to say that the Florence Charter’s reference to plant propagation also emphasized the importance of preserving the genetic heritage of historical times and ecosystems.

The Széchenyi lime tree allée with its methuselah trees could and should be seen as a genetic heritage reservoir. In the 2024 survey, we identified 99 old and 119 medium-aged trees still in good or acceptable condition reflecting their will to survive and announce the creator’s large-scaled landscape design to leave a sign for centuries. Among these, we characterized 26 individuals (15 ancient, 11, medium aged trees) that have spectacular, dense crowns and apparently tolerate the drying climate well even without irrigation (Figure 11). They can be excellent raw materials for passing on their genetic material to the future.

4.3. Landscape Evaluation of the Greenway Condition and Management

The overall character of the allée greenway has changed since the 2019–2020 restoration work due to the decreasing level of maintenance. Thanks to the cleaning and cutting works along the greenway and in the canopies the grass layer could recover, the weeds and weed trees disappeared. The improvement of the habitat, the decrease of competition for ecological sources resulted in clearly visible development of old and young trees too. Unfortunately, the full implementation of the greenway management plan stopped about two years ago, and the allée maintenance decreased again to the simple extensive mowing works in the walking pathway. There is a clearly visible difference between the first and second allée sections (from the castle garden to the railway line and over the embankment to the terminating grove) in their habitat character and ecological condition due to the different level of maintenance. In the first section, the central walkway is still acceptable with its semi-extensive mowing, but the side lawns are left to grow high, and the grass layer is polluted again by weedy plants. In the second section, due to the neighbouring agricultural land use forms, the habitat is severely damaged by the regular, though illegal traffic of heavy agricultural machines; the result is a bad soil compaction and the extinction of the grass layer. On the other hand, the allée’s main axis to the south is destroyed by a new wind energy farm, where year-by-year new wind turbines appear in the landscape (in 2018 only one, in 2022 two and in 2024 three wind turbines rise and disturb the harmony of the World Heritage Site, the Széchenyi castle, and its landscape) (Figure 12).

Climate change effects accelerated drastically in recent years overall in the mid-European region with long drought periods, decrease of precipitation, and soil water level. The slight decrease of the number of trees along the allée talk about trees’ suffering of the current level of maintenance, the lack of the complex heritage protection works. Still, many old, let us say, heritage trees survive within these habitat conditions, which underlines the importance of the conservation of the genetic heritage. Hence, a new plantation and a full allée reconstruction might struggle for life within these environmental circumstances and with a possible low maintenance quality.

4.4. The Széchenyi Linden Allée as a Baroque Garden Design Creation

The cultural and even the living heritage protection concepts embedded in the international ICOMOS-IFLA charters underlines the authenticity as a set of design and functional aspects. In the case of gardens topped by the restoration of plant layers [17] and more definitely in the NARA Document launched in 1994, increasing authenticity on a higher level and calling it the essential issue of a quality reconstruction [24]. Gardens are dynamic, fluently developing, changing creatures as time goes by and their sustainability depends mainly on the planting material’s life cycle. The turns of functional and management systems along the centuries, topped by human-made or natural disasters and more recently, the effects of climate change may regress the authenticity aspect of historic gardens a questionable, difficult-to-achieve goal. In the case of allées, the plant material, the tree selection, the directions and proportions, the design of the greenway, and the entrance and termination sections are the relevant, measurable, and surveyable factors created by the original design and moderated by evolution, development, functional, and ecosystem changes (Figure 13).

As a Baroque garden creation, the Széchenyi linden allée has lost a lot of its original, designed character, though the plantation rhythm is still recognisable (measured in the 2011 allée survey). Due to the natural ageing of old trees, the non-authentic replantation actions in the late 20th century topped with the low-level maintenance even in the early 21st century, the allée lost its once uniform character. Sectioned by empty tree places or short, void sections, the allée is still the magnificent creation of Hungarian Baroque garden art. It would need distinguished attention based on its rarity value in Hungary and even in Central Europe. The present fragmentation by the railway line and the severe habitat destruction of agricultural land use cry for solution. The allée should be seen as a unified garden art creation with no differences in maintenance and land-use intensity. Though the railway line obviously remains a linear separate unit, the functional unity should be restored with possible technical solution, as proposed in the 2018 allée reconstruction concept plan.

5. Discussion

The historic allée of Nagycenk has a high cultural significance based on all value aspects listed in the Burra Charter. The aesthetic value of the Baroque garden and landscape composition, though smoothly blended into the landscape due to passing centuries and the natural aging of the tree stock; The historic relevance of the Széchenyi family, especially Ferenc and István Széchenyi who played a determining role in the cultural, scientific, economic, and land-management field, and beyond all this, the exemplary leading role in the Hungarian social development, the enlightenment, and national awakening of the so-called reform age. The scientific importance of the 2,5-centuries old gene reservoir of the still existing ancient trees, and the lessons learned from the earlier allée management actions, the false restoration methods, the societal significance lies in the fact that the allée was cherished and maintained by many generations, despite the changes in the ownership and responsibility, and the landscape and environmental system of the whole habitat.

The ecological challenge of the 21st century is severe all over the world due to climate change. Unfortunately, the ecological changes are increasingly threatening, to mention only the most serious problems like rainwater precipitation, lingering and dramatic heat waves, and heavy storm events. Within the overall, structured plantation of gardens, the tree canopy seems the most vulnerable living system threatened by changing climate elements. This is especially true for the hundreds year old mature tree stock of historic gardens with. The original composition, the artistic, design aims, and the traditional planting design carry aesthetical, cultural values, and character. The modification of plant society to sustain the garden with an adaptative vegetation would be far from the authentic reconstruction and might destroy the heritage. A step-by-step replantation with new specimen and a greater variety of taxon seem reasonable and sustainable. On the other hand, allées, even Baroque allées are more sensitive creatures from design and heritage protection view. The homogeneous character of allées could be an authenticity expectation for the preservation plan, even if the allées are not pruned in architectural forms any more

The contradictions of the aspects of authenticity and sustainability are difficult to resolve, at least in the case of historic allées, but in the example of the Széchenyi linden allée, we think that the species or genus can be an authenticity criterion, while the genetic diversity could be the basic principle within this. Propagation that preserves the ‘Nagycenk’ gene heritage seems a promising possibility, although the diversity of the current linden tree nursery material is still low.

It is evident that climate change can result in a changed habitat for plants first of all in cities and in the open or natural landscape [25]. The adaptation mechanisms of plants enable the survival of some individuals and stocks if the variability of the stock is high enough. All over the cities, instead of the traditional uniform or a per-rows-limited variety of urban allées, a sort of mixed plantation seems to be a new trend to reduce the possible tree losses. These tendencies are increasingly accepted in the case of urban allées and avenues [26], but not really tolerated in the case of Baroque tree allées, where the diversity at the genus level would not answer the authenticity required [16,27]. Therefore, the linear arrangement within the genus consisting of individuals of several species but with similar crown shapes and habitus can remain. And ideally, the individuals are not vegetatively propagated trees with the same genetic stock, but they are basic species grown from seed with a high genetic variability. In the case of the linden allée in Nagycenk, this means mainly the individuals of Tilia cordata, T. platyphyllos, and T. tomentosa.

5.1. Exemplary Reconstructions of Lime Tree Allées

All over, Baroque Europe large-scaled linear green compositions appeared within royal and noble gardens, along the main routes, and in most cases, the strict architectural form to create space borders, to connect castles and hunting parks, or to help local and regional traffic. Many of these monumental creations disappeared due to stylistic change, land-use reutilisation, land or urban development, and natural or human-made disasters. Among the still-existing Baroque allées, only a few could survive, at least partially, in their original tree plantation material. Here, we can summon only a few allée reconstructions different in their planting design methods.

The already mentioned Blenheim Grand Avenue is a good example for a total reconstruction, because the original elm trees had to be felled due to a tree-specific disease, and the replantation went on with a new tree species. The 1970s linden tree allée would need a replantation sometime in the 22nd and 24th centuries according to the Blenheim Master Plan [5]. Even a new replantation idea appeared in the plan, proposing the planting of a second allée, outside and parallel to the existing rows in the 21st and 23rd centuries to build a rotation possibility in this way. Changing the tree species was not included in the plan, but it is true that when the plan was drawn up, climate change did not yet appear to be a worrying climate trend.

The many amazing Baroque allées let us evoke the Herrenhäuser Allee in Hanover, which is one of the very earliest large-scaled linear garden compositions with its 300 year old creation (planted in 1726) The four rows of lime trees running over one-mile distance (≈1850 m) connected the Herrenhäuser royal palace and gardens to Hanover, the city. No replantation was needed until the 2nd WW when the military actions, severe bombing, and post-war military land use caused severe damage to the trees and the whole greenway. After a full habitat restoration, the authentic reconstruction went on in the late 1970s [28].

5.2. Evaluation of Tree Management Process of the Széchenyi Allée

The tree care trends of the previous years brought mixed results in the Széchenyi allée at Nagycenk were clearly detected by the 2022 and 2024 surveys. There are individuals that seemed promising for a longer or at least medium-term survival in the 2022 review, but by 2024, their condition has badly deteriorated, so they could stay only in the short term (like no. 168, 175, and 186 trees). Fortunately, we found examples for the opposite case, where the condition turned to a better status from 2022 by 2024 due to the new, airy tree canopy (like no. 187, 203, and 208 trees).

5.3. Preservation and Reconstruction Possibilities for the Széchenyi Allée

The unbalanced ecological situation and the effects of climate change cause more and more problems in terms of habitat management, decreasing groundwater systems, and the lack of buffer water bodies. While the 2011 allée investigation attributed the speeded deterioration of the allée primarily to the lack of maintenance and the environmental load of the neighbouring agricultural and forest land-use system, the 2018 survey detected the increasing problems and destruction caused by climate change like the drying habitat and storm damages of old trees. These problems occurred more intensively during the 2022- and 2024 years’ investigations. Therefore, the original idea of reconstructing the historical allée with a full replantation [9] may require severe revision.

A new reconstruction concept plan should be based on sustainability and resilience aspects due to the changing environment and the present lack of management budget. For this, the planting of lime trees propagated from the original genetic stock must be increased to preserve the genetic heritage of trees with long life capacity and strength; furthermore, the genetic variety of propagation should be increased in the next reproduction program of the tree nursery. The proportion of residual trees of all life categories should also be risen to present and highlight the historical value of the heritage allée. Old lime trees in good condition should stay for a longer period like so-called witness trees.

In the name of resiliency, the replantation in the authentic rhythm might be also questionable. The young trees planted in an intermediate position sometime in the late 20th century grew well in the past years as they could utilise the new, airy habitat after the 2019–2020 allée management. Hence, it is worthwhile to give chance to these young trees to survive, even if the result would be a different rhythm because they seem to stand the climate. With all these solutions, as the trees grow, the time for medium and long-term allée management will arise to restore the original plantation system by replantation of genetically authentic propagation trees and the fell of young trees planted in-between positions. Unfortunately, the idea of creating temporary or preview tree lines behind the present plantation rows is impossible due to the land-use system, the neighbouring agricultural and forest cultivation, and the property conditions.

Genetic variability, at least on the Linden tree clan level, is the key element of a resilient reconstruction program. Therefore, the tree nursery of the original Széchenyi linden trees (mainly Tilia cordata and T. platyphyllos) should go on with a wider selection of long-lived, strong, mature trees. The preservation of the present medium and young allée trees also improves the genetic diversity. The short and medium-term maintenance, management, and ongoing restoration program should be based on complex habitat protections and improvements to decrease the effects of worsening climate change. The sustainability of heritage preservation depends on overall habitat protection, the integration of groundwater system management, and even the creation of buffer water bodies, as the lack of groundwater decreases the crown’s health too.

The last but essential question is the timing and sectioning of allée restoration works. The Széchenyi linden allée is a 2.3 km-long creation cut into two parts by the regional train line. The greenway of the second section is hard to approach due to the railway embankment without any legal, built crossing. The allée, our valuable national heritage, terminates at the grove, which is a memorial and grave garden of the Széchenyi family. The heritage preservation program should propose the construction of a railway crossing and the one-sectioned reconstruction and replantation of the Széchenyi allée.

6. Conclusions

Reflecting on the landscape architectural, natural, and cultural-historical value of the linden allée, it is worth quoting here András Balogh, the former professor of art history, design, and drawing at the University of Horticulture, Budapest: “What kind of forethought and sacrifice is required to, for example, in the case of the Nagycenk allée, someone planted 2 rows of linden saplings 25 m apart, in an endless length, of which’s magnificent tree canopy not they themself, but a third or sixth generation will enjoy while walking.” [29].

The painter András Balogh immortalized the row of linden trees in Nagycenk in a beautiful oil painting (Figure 14). The row of trees appears in the picture as a creature of nature and wide-ranging creative imagination. The unique character of the two-century-old trees that make up the model and the generosity of the vue they create are captivating. The row of trees, true to the Baroque spirit, dominates the landscape, but the painter’s brush also shows individual trees; centuries of events unfold before us. The shape of old trees speaks of the past, the history of development, environmental and ecological changes, and the work of caring or less caring hands. More than half a century has passed since the birth of the painting. The ancestors of the trees in Nagycenk, therefore, date back to a past of more than two and a half centuries. The once uniform, magnificent row of trees is now cracked. Due to the old trees dying one by one, the unprofessional replacements, the stagnation of maintenance after the renewal treatment, the characteristic rhythm, and the almost closed, vaulted view created by the crowns have been lost. Ancient trees die at an accelerated rate, at the “legs” but quite a few trees survive thanks to their root shoots. Most of the saplings that were unprofessionally planted among dying trees were able to benefit from the more open stock and habitat characteristics due to crown pruning. The creation of landscape architecture is a delicate heritage, as the landscape and landscape use change, and trees age irrevocably. The question inevitably arises: is the value of the trees or rather the row of trees formed by them? Instead of linden and ancient trees, saplings were planted in the gaps between the trees where they will be able to faithfully pass on the large-arched work of the Széchenyis, so that hopefully the “third or sixth generation” will be able to enjoy a walk under the vaulted crowns. This is an eternal dilemma in the case of garden architecture works. But, the creative intention itself is part of the heritage, especially when it comes to our defining historical figures. Unfortunately, the initial energetic works of the development increased the value and attractiveness of the Fertő-táj World Heritage Site and expanded its functions, but came to a halt due to economic and development restrictions. We can only trust that the authentic and value-preserving renewal of the tree row can be given the green light, and in the meantime, there is time to strengthen the tree row population, and especially to develop a sustainable, flexible, scheduled renewal method for the Baroque horticultural work of Central European importance, the tree school program aimed at preserving genetic heritage for revitalization, protection, and improvement of habitat features. The future of the Széchenyi linden row in Nagycenk is an essential heritage protection issue.

The theoretical and ethical basis of the renewal programme is the preservation of the natural, landscape aesthetic, and intellectual heritage of the Széchényi family at Nagycenk. At the time, when the idea of regeneration was first mooted, the habitat had not yet changed significantly, and the small-leaved linden (Tilia cordata) would continue to find favourable living conditions here. The original idea was that the preservation of spiritual, charitable, and ecological values could only be ensured by a complete regeneration of the same gene. The necessary propagating material would be propagated from plant specimens on the site. Restoration and replantation of the allée should be carried out not later than 20–25 years. Thus, the entire renewal would be carried out in several stages, planting trees of the same age and size, and the overall appearance of the allée will be uniform within a short time. The authenticity of the gene-identical renewal is undeniable: the restored allée would provide an authentic view and a reconstruction as close as possible to the original design intent. The preservation of the about 270-year-old gene pool could be an important scientific achievement. From the botanical point of view, the propagation of the old gene heritage of its strong vitality might be an essential experiment, while the set of propagated “heritage” trees play an important cultural role, promoting the long-term thinking of the Széchenyi family.

Although we know from the Shifting Baseline Syndrome (SBS) phenomenon that newer and newer generations consider the status quo as the basic principle [30,31], we have reached the consensus that the conservation of the historical value of the linden tree allée in Nagycenk is primarily expressed in the preservation of the genetic heritage of the remaining individuals. In the more distant future, it is conceivable that the planting of linden taxa with similar habits and appearance but with better drought tolerance could be considered alongside the native linden trees.