A Botanical Analysis and Price Comparison of Wildflower “Seed Bombs” Available in Ireland

Abstract

Small areas of flowering plants within urban landscapes can provide much-needed nutrition, shelter, and host plants for pollinating insects and other wildlife. To create such floral displays in gardens, shared spaces, and derelict properties, the use of ‘seed bombs’ (or ‘bee bombs’) is a popular, convenient method for individuals and community groups. Recently, however, the value of seed bombs and wildflower seed mixes has been questioned in terms of seedling establishment, the numbers of species they contain, and whether these species are actually native ‘wildflowers’ as is often claimed. In this study, we obtained 12 brands of seed bombs available in Ireland, with prices ranging from €0.33 to €2.66 per seed bomb. We processed five seed bombs per brand and identified 3083 seeds belonging to 63 species in 22 plant families. The most frequent plant species were Papaver rhoeas L., Phacelia tanacetifolia Benth., and Trifolium alexandrinum L., none of which are native to Ireland. No brands contained only native Irish plants, and one brand obtained from Germany contained no native Irish species. Multivariate analysis identified a cluster of seven brands with similar plant species composition, suggesting they were from the same source or made to the same specifications. Our results suggest that although seed bombs offer a convenient method of producing mixed-flower habitat patches, consumers should be wary that the number of species they contain can be low, they are likely to contain non-native species, and high prices may not reflect the quality of their contents.

1. Introduction

Insect pollinators are undergoing dramatic global declines in terms of abundance, diversity, and geographical range. These declines are attributed to several factors, including habitat loss, agricultural intensification, climate change, and the increased prevalence of parasites and pathogens [1,2,3,4]. Associated with a loss of high-quality natural habitats, insect pollinators are exposed to nutritional deficits caused by low abundance of floral resources [5], which in turn can exacerbate the negative impacts of pesticide exposure and infection by pathogens [6,7]. In urban/peri-urban settings, there is growing evidence that the establishment of small areas of flower-rich habitats in private gardens, shared community spaces, road verges, and traffic islands, can help mitigate insect nutritional deficits [8,9,10]. Convenient and cost-effective ways of creating these florally rich areas include the use of commercial mixed seed blends, ‘wildflower’ seed packets, or by using ‘seed bombs’ or ‘bee bombs’. Seed bombs are mixtures of flower seeds, compacted into balls of clay, compost, or soil, and are widely available from general stores, garden centres, and online sellers. All of these products are often promoted as containing wildflowers, being of benefit to pollinating insects and other wildlife, and as an ecologically friendly method of producing floral patches or ‘mini meadows’ [11].

Several empirical studies have demonstrated that the flowering plants produced by ready-made seed blends can enhance pollinator abundance and species diversity [12,13,14]. Conversely, other reports have advised caution, expressing concerns that references to ‘wildflowers’ and ‘natural habitats’ on packaging may be misleading [11,15,16,17,18]. Many of the plant species included in these seed blends are not native to all the countries in which they are sold, and the suite of species they contain may not represent any plant assemblage that would naturally occur [11,19,20]. From an ecological perspective, there are clearly issues with introducing non-native species, or ornamental or agricultural varieties, into the wider environment, including competition with local flora, hybridization, and the potential for species to become invasive [20].

In an Irish context, Barry and Hodge [11] analysed several brands of mixed seed blends where packaging indicated the contents were wildflowers, or that the plant mix had been specifically designed to benefit pollinators such as bees or butterflies. Overall, only 43% of the 90 plant species in the seed blends were native to Ireland, and there was little or no evidence provided that any seeds had Irish provenance. Similarly, Smyth [21] examined seed mixes for sale in major retail stores in Ireland and found that only 25% of species listed on packaging were Irish native plants, with many species originating from America, Asia, or Africa. In Italy, Nota et al. [22] reported that alien plant species were prevalent in ‘wildflower’ seed mixes aimed at pollinator conservation and could pose a serious threat to native biodiversity and habitat conservation.

The manufacturing and use of seed bombs has a long history, previously being employed as a labour-saving practice in agricultural and forestry to sow seeds over wide areas [23]. More recently, because they provide a means of quickly reaching inaccessible waste land, seed bombs have been associated with the concept of ‘guerilla gardening’, where flowering plants are deliberately introduced to unused urban spaces, both for aesthetic reasons and to enhance local biodiversity [24,25]. Although this repurposing of waste ground might be based on good intentions, the value of commercially produced seed bombs has been questioned because of low rates of seed germination, low species diversity, and low plant establishment. For example, Anderson and Minor [26] reported that seed bombs resulted in the lowest levels of plant establishment when compared with methods such as seed broadcasting and the use of seedling plugs. Similarly, Alton and Ratnieks [27] indicated that reviews of seed bombs by online consumers frequently mentioned low germination rates, low plant establishment, and lack of persistence over multiple seasons.

The overall objective of this study was to complement the studies of Barry and Hodge [11] and Smyth [21] on mixed flower seed packets, by providing a similar assessment of the botanical composition and economic value of seed bombs available in Ireland. Specifically, we aimed to gain information with respect to both the potential conservation value and the ecological risks associated with the use of seed bombs in an Irish context, and to compare the species profiles in different seed bomb brands. To achieve these aims, we purchased twelve different brands of seed bombs via online sellers, and collected data on variables relating to seed contents, plant biogeographic status in Ireland, and cost.

2. Materials and Methods

2.1. Obtaining Seed Bombs

Twelve different brands of seed bombs were obtained from online sellers between December 2023 and June 2024. The sellers were all based within the European Union and their products were all purchasable online from Ireland. Nine seed bomb brands were obtained from sellers within Ireland, two brands were obtained from sellers in Germany, and one from the Netherlands (

Table 1. Summary of twelve wildflower seed bombs purchased in Ireland in 2023/24: name of brand, country produced in, price (€) per pack, number of seed bombs per pack, webpage purchased from, and date of purchase. All webpages were accessed on the Date of Purchase. Brand code refers to the code we assigned to each brand for the purpose of this study. Composition: C = clay, SL = soil/compost, PA = paper. Extraction: SK = soaked, PM = pestle and mortar, SV = sieved.

Brand Code	Product Name	Date of Purchase	Origin	Website	Composition	Extract Method	Extraction Efficiency (%)
IRE01	Faerly	3 January 2024	Ireland	https://www.faerly.ie	C + SL	SK	99
IRE02	Plants and Extracts	8 February 2024	Ireland	https://www.plantsandextracts.ie/	C + SL	SK	100
IRE03	Seedbomb	14 December 2023	Ireland	https://seedbomb.ie/	C + SL	SK	100
IRE04	Signature Editions	10 April 2024	Ireland	https://signature-editions.ie/	C + SL	SK	100
IRE05	Beebombs	14 December 2023	Ireland	https://www.beebombsireland.com/	C + SL	PM + SK + SV	Na
IRE06	We Make Good	3 January 2024	Ireland	https://wemakegood.ie/	SL + PA	PM	100
IRE07	Field Day	1 June 2024	Ireland	https://kilkennydesign.com/	SL	SK	100
RE08	Irelands Beeswax Wraps	3 January 2024	Ireland	https://irelandbeeswaxwraps.ie/	SL	SK	99
IRE09	Erva	12 April 2024	Ireland	https://erva.ie/?v=b2b941e46c50	C + SL	SK	100
GER01	Passions Products	22 May 2024	Germany	https://www.etsy.com/ie/shop/PassionProductsDE	PA	SK	100
GER02	Seedball Factory	12 April 2024	Germany	https://seedball-factory.com/	C + SL	PM + SK + SV	Na
NET01	Naturally’s Blossombs	8 February 2024	Netherlands	https://www.blossombs.fr/en	C	PM + SK + SV	Na

). Enough packets of each brand were purchased to enable five individual seed bombs to be processed. Table 1 summarises information pertaining to the purchasing website, price of each packet, price per seed bomb, country of origin, date of purchase, and whether a plant species list was provided (online or on actual packaging) for each of the 12 brands.

2.2. Seed Extraction and Identification

Five seed bombs per brand were individually weighed and processed so that seeds could be extracted. Depending on the composition of the seed bomb, some seed bombs were broken down using a pestle and mortar (with minimal force to reduce the risk of crushing seeds), whereas others were first soaked in water to soften the packing material (e.g., paper, clay, sand, silt) (Table 1). All materials from the seed bombs were placed into a Petri dish and seed extractions performed under a low-power dissection microscope. All leftover materials from each processed seed bomb were retained. For nine of the twelve brands, material from one seed bomb was subsequently re-examined to ascertain the efficiency of the primary seed search. Three brands were processed using a combination of soaking, crushing with pestle and mortar, and then flushing through a fine sieve, which resulted in no leftover material to re-examine (Table 1).

When possible, seeds were identified by comparison, with reference images for the species listed for each brand. On other occasions, extracted seeds were identified using a suite of physical features (size, colour, texture, structure) and consulting the website seedidguide.idseed.org. Seeds that could not be identified through these methods were planted in 7 cm square plastic pots filled with a general potting compost and maintained under glasshouse conditions for two months. If the seeds germinated, the identification of the seedlings was carried out using the PlantNet (version 3.23.5) phone app, the webpage www.wildflowersofireland.net, and Collin’s Wildflower Guide [28]. Species were initially designated as either native or non-native to Ireland by consulting the online resource provided by Seawright [29], with subsequent reference to Devlin [30], Barry and Hodge [11], and Smyth [21] to gauge consistency.

2.3. Calculations and Statistical Analysis

All data collation and basic calculations were performed using Microsoft Excel. For each brand of seed bomb, data were collected on seed bomb weight, number of seeds per bomb (including identified and unidentified seeds), and number of plant species per bomb (only identified seeds). For the price analysis, data were collected on price per bomb, seeds per euro, and species per euro. Relationships between price and other numerical variables (e.g., total seed count, number of species, proportion of native plant species) were assessed using Spearman’s rank correlation coefficient (SPSS Statistics v27, IBM Corporation, Chicago, Illinois, USA). Spearman’s rank correlation was used as it measures the strength of monotonic relationships, regardless of whether the relationship is linear or non-linear.

It was desirable to compare the species compositions of the seed bombs, to see if certain brands used similar plant species (and in similar proportions). Additionally, we wanted to identify any outlying brands, in terms of what plant species the seed bombs contained. To meet this aim, we performed multivariate non-metric multi-dimensional scaling analyses (NMDS; Community Analysis Package, Pisces Conservation Ltd., Hampshire, UK). These analyses were carried out using only the data for those seeds that could be identified at species level. Two versions of the raw data were used: (1) the presence or absence of each plant species within each brand, and (2) the total number of seeds of each species in the five processed seed bombs for each brand.

3. Results

3.1. Seed Bombs: General Properties and Price Comparison

A variety of materials were used as the seed bomb packing matrix, including clay, compost, soil, shredded paper, or combinations of the above (Table 1). Most of the seed bombs required some soaking to extract the seeds, but, overall, the efficiency of the seed extraction process (from the nine brands examined) was very high (>99%; Table 1). Of the twelve brands of seed bombs, only six provided a species list as part of the packaging or in the online product information (

Table 2. Profiles of twelve brands of wildflower seed bombs purchased in Ireland in 2023/24, based on their seed contents. For brand details see Table 1. Bomb weight, seeds per bomb, species per bomb are the mean of five bombs. Total species and native species (%) are based on pooled data for all five bombs.

Brand Code	Spp List Provided	Bombs per Pack	Bomb Weight (g)	Seeds (per Bomb)	Species (per Bomb)	Species (5 Bombs)	Native Species (%)
IRE01	No	10	0.83	39.8	6.8	13	92
IRE02	No	10	1.67	23.6	6.8	12	75
IRE03	Yes	10	1.99	24.2	6.8	11	82
IRE04	No	10	1.71	24.4	4.2	9	78
IRE05	Yes	21	4.52	47.2	9.4	16	56
IRE06	No	3	40.39	5.0	3.0	8	63
IRE07	No	5	1.25	56.4	10.0	14	86
IRE08	Yes	5	1.53	72.6	13.0	24	83
IRE09	Yes	5	1.62	26.6	6.6	13	85
GER01	No	10	2.92	77.4	15.0	19	47
GER02	Yes	10	4.4	142.0	7.2	11	0
NET01	Yes	6	5.7	77.0	9.2	11	25

).

In total, 3083 seeds belonging to 22 plant families and 63 plant species were extracted from the 60 seed bombs we processed. Most of the seed bombs weighed between 1 and 2 g, but the heaviest were from the brand IRE06, at over 40 g. Even though IRE06 were the heaviest bombs they contained the fewest number of seeds, with an average of only five seeds per bomb, almost 30 times fewer than the GER02 brand, which had an average of 142 seeds per bomb. Most brands, with the exception of IRE07, IRE08, and GER01, contained fewer than 10 species per seed bomb (Table 2). GER01 was the most species-rich brand, containing an average of 15 species per bomb, whereas IRE06, although having the heaviest seed bombs, was the least species-rich, with only three species per bomb. IRE06 also had the fewest species in total when pooled over all five seed bombs (8 species), whereas IRE08 had the highest total number of species at 24 (Table 2).

With respect to cost, at the time of purchase, GER01 was the cheapest brand, priced at €3.30 per pack of ten, while NET01 was the most expensive, at €13.50 euros per packet of six (

Table 3. Price profiles of twelve brands of seed bombs purchased in Ireland in 2023/24, based on their average price, weight, and seed contents per bomb (see Table 1 and Table 2).

Code	Price (€) per
	Pack	Bomb	Gram	Seed	Species
IRE01	6.39	0.64	0.77	0.016	0.09
IRE02	10.00	1.00	0.60	0.042	0.15
IRE03	8.00	0.80	0.40	0.033	0.12
IRE04	10.00	1.00	0.58	0.041	0.24
IRE05	7.99	0.38	0.08	0.008	0.04
IRE06	8.00	2.66	0.07	0.532	0.89
IRE07	13.00	2.60	2.08	0.046	0.26
IRE08	4.25	0.85	0.56	0.012	0.07
IRE09	5.00	1.00	0.62	0.038	0.15
GER01	3.30	0.33	0.11	0.004	0.02
GER02	4.90	0.49	0.11	0.003	0.07
NET01	13.50	2.25	0.39	0.029	0.24

). GER01 was the cheapest price per bomb at €0.33, whereas IRE06 was the most expensive price per bomb at €2.66 euros (Table 3). Cost per gram of seed bomb also varied considerably among brands: being by far the heaviest seed bombs, IRE06 had the lowest per weight cost at €0.07 per gram, whereas IRE07 was almost 30 times more expensive at €2.08 per gram (Table 3).

Across all 12 brands, there were no significant relationships between the price of the seed bombs (per packet) and any of the measures of ‘quality’ that we used: seed bombs per pack, number of seeds per pack, total weight of seed bombs per pack, species per seed bomb (and per five bombs), and the proportion of native Irish species (Figure 1). The strongest relationships identified were between price per pack and species per bomb (r_s = −0.31, p = 0.331), and total species per five bombs (r_s = −0.51, p = 0.09), albeit these relationships were negative due to some of the cheapest brands (IRE08 and GER01) containing the most plant species (Table 2 and Table 3; Figure 1).

In terms of seed quantity, GER02 provided the best value for money, with approximately 290 seeds per euro (€0.003 per seed; Table 3), whereas IRE06 provided the least value for money, offering fewer than two seeds per euro (€0.53 per seed). In terms of price per species, GER01 was the most economical, costing just €0.02 euros per species on average. Because there were so few species present in brand IRE06, this brand had the highest average price, at €0.89 per plant species (Table 3).

3.2. Taxonomic Composition of Seed Bombs

The twelve brands of seed bombs contained a total of 22 plant families, with the most frequent families being Asteraceae (in all 12 brands), Papaveraceae (11 brands), Caryophyllaceae (9), Plantaginaceae (8) and Lamiaceae (8) (

Table 4. Plant families found within twelve brands of seed bombs purchased in Ireland in 2023/24. See Table 1 for details of each brand.

Family	IRE01	IRE02	IRE03	IRE04	IRE05	IRE06	IRE07	IRE08	IRE09	GER01	GER02	NET01
Amaranthaceae	-	-	-	-	-	-	-	-	-	√	-	-
Apiaceae	-	√	√	-	√	-	-	√	-	√	√	√
Asteraceae	√	√	√	√	√	√	√	√	√	√	√	√
Boraginaceae	-	√	-	-	-	√	-	-	-	-	√	√
Brassicaceae	-	-	-	-	√	-	√	√	-	√	-	√
Caprifoliaceae	-	-	-	-	-	-	-	√	-	-	-	-
Caryophyllaceae	√	√	-	√	√	-	√	√	√	√	-	√
Fabaceae	√	-	√	-	-	√	-	√	√	-	√	√
Gentianaceae	-	-	-	-	-	-	-	√	-	-	-	-
Hypericaceae	√	√	√	√	-	-	√	√	-	-	-	-
Lamiaceae	√	√	√	√	-	-	√	√	√	√	-	-
Linaceae	-	-	-	-	-	-	-	-	-	√	-	-
Lythraceae	√	√	√	√	-	-	√	√	√	-	-	-
Malvaceae	-	-	-	-	-	-	-	-	-	-	√	-
Onagraceae	-	-	-	-	-	√	-	-	-	-	-	-
Papaveraceae	√	√	√	√	√	-	√	√	√	√	√	√
Plantaginaceae	√	√	√	√	-	-	√	√	√	-	-	√
Poaceae	-	-	-	-	-	√	-	-	-	√	-	-
Polygonaceae	√	-	-	-	√	-	-	-	-	-	√	-
Ranunculaceae	-	-	-	-	√	-	√	√	√	√	-	√
Rosaceae	-	-	-	-	√	-	-	√	-	√	-	-
Rubiaceae	√	-	-	-	-	-	√	√	-	-	-	-

). Seeds of species in the Apiaceae, Fabaceae, and Lythraceae families occurred in seven of the twelve brands, whereas six plant families were recorded in only a single brand each: Amaranthaceae, Caprifoliaceae, Gentianaceae, Linaceae, Malvaceae, and Onagraceae (Table 4).

From the 60 seed bombs we processed, a total of 63 plant species were identified using seed morphology or, to a lesser extent, using germinated seedlings (Appendix A,

Table A1. Plant species found in 12 brands of seed bombs available online in Ireland. Numbers are the total numbers of seeds found in five seed bombs of each brand. Details on the origin and cost of each brand are provided in Table 1 and Table 2 in the main text.

Family	Species	Native	Family	Species	Native
Amaranthaceae	Amaranthus blitum	No	Fabaceae	Lathyrus pratensis	Yes
Apiaceae	Anethum graveolens	No		Melilotus officinalis	No
	Coriandrum sativum	No		Ornithopus sativus	No
	Daucus carota	Yes		Pisum sativum	No
Asteraceae	Achillea millefolium	Yes		Trifolium alexandrinum	No
	Anthemis arvensis	No		Trifolium pratense	Yes
	Centaurea cyanus	Yes		Trifolium repens	Yes
	Centaurea nigra	Yes		Trifolium resupinatum	No
	Glebionis segetum	No		Vicia sativa	No
	Helianthus annuus	No	Gentianaceae	Gentiana verna	Yes
	Leucanthemum vulgare	Yes	Hypericaceae	Hypericum perforatum	Yes
	Matricaria chamomilla	No	Lamiaceae	Prunella vulgaris	Yes
	Rudbeckia hirta	No		Salvia officinalis	Yes
	Silybum marianum	No		Thymus serpyllum	No
	Tagetes erecta	No	Linaceae	Linum grandiflorum	No
	Tripleurospermum inodorum	Yes	Lythraceae	Lythrum salicaria	Yes
Boraginaceae	Borago officinalis	No	Malvaceae	Malva sylvestris	No
	Phacelia tanacetifolia	No	Onagraceae	Epilobium tetragonum	No
Brassicaceae	Arabidopsis thaliana	Yes	Papaveraceae	Papaver rhoeas	No
	Camelina sativa	No		Papaver somniferum	No
	Cardamine parviflora	No	Plantaginaceae	Digitalis purpurea	Yes
	Cardamine pratensis	Yes		Plantago lanceolata	Yes
	Matthiola longipetala	No		Veronica chamaedrys	Yes
Caprifoliaceae	Knautia arvensis	Yes	Poaceae	Lolium perenne	Yes
Caryophyllaceae	Agrostemma githago	No	Polygonaceae	Fagopyrum esculentum	No
	Cerastium fontanum	Yes		Rumex acetosa	Yes
	Gypsophila elegans	No	Ranunculaceae	Caltha palustris	Yes
	Gypsophila vaccaria	No		Nigella sativa	No
	Silene dioica	Yes		Ranunculus acris	Yes
	Silene flos-cuculi	Yes		Ranunculus bulbosus	Yes
	Silene latifolia	No	Rosaceae	Sanguisorba minor	Yes
			Rubiaceae	Galium verum	Yes

). Although 36 unknown sets of seeds were sown in pots, only eight (22%) produced seedlings that allowed for species identification. The most numerous plant species in terms of seed number was Phacelia tanacetifolia Benth. (Boraginaceae), with a total of 517 seeds across the twelve brands (

Table 5. The most common plant species occurring in seed ‘bombs’ available in Ireland, based on the total number of seeds and the number of brands (from 12) in which the species occurred. Names in bold represent native Irish plant species.

Rank	Species	Seed Count	Species	Brands
1	Phacelia tanacetifolia Benth.	517	Papaver rhoeas L.	10
2	Trifolium repens L.	411	Phacelia tanacetifolia Benth.	9
3	Prunella vulgaris L.	262	Trifolium alexandrinum L.	8
4	Lythrum salicaria L.	244	Lythrum salicaria L.	7
5	Papaver rhoeas L.	214	Leucanthemum vulgare Lam.	7
6	Malva sylvestris L.	91	Papaver somniferum L.	6
7	Linum grandiflorum Desf.	85	Matthiola longipetala (Vent) DC	6
8	Trifolium alexandrinum L.	68	Achillea millefolium L.	6
9	Centaurea cyanus L.	67	Caltha palustris L.	6
10	Papaver somniferum L.	63	Veronica chamaedrys L.	5

). The second most numerous species, with a total of 411 seeds, was white clover, Trifolium repens L. (Fabaceae), and the third most numerous species was Prunella vulgaris L. (Lamiaceae) (Table 5). Trifolium repens and Prunella vulgaris are considered native to Ireland, whereas Phacelia tanacetifolia is not native to Ireland, and originates from south-western USA and Mexico. In terms of the most frequent occupants of the seed bombs, the most commonly occurring species were Papaver rhoeas L. (10 brands), Phacelia tanacetifolia (9 brands), and Trifolium alexandrinum L. (8 brands) (Table 5). None of these three plant species are native to Ireland.

From the 63 plant species that could be identified, we considered only 30 (48%) as being strictly native to Ireland. None of the seed ball brands contained 100% native Irish plant species: one brand, IRE01, contained 92% Irish natives (12/13 species), whereas at the other extreme, brand GER02, which we obtained from Germany, contained no plant species native to Ireland (Table 2). However, of the 15 plants that were ranked in the highest 10 species based on seed number and/or brand presence, eight are considered as being native Irish species: Achillea millefolium L., Caltha palustris L., Centaurea cyanus L., Leucanthemum vulgare Lam., Lythrum salicaria L., Prunella vulgaris L., Trifolium repens L., and Veronica chamaedrys L. (Table 5).

3.3. Multivariate Analysis of Seed Species Composition

As stress values in both NMDS analyses were slightly greater than 0.2, some caution is needed when interpreting these results. Nevertheless, the NMDS analyses using seed counts and using species presence–absence both indicated that there was a distinct cluster of seven seed bomb brands, based on their plant species composition (Figure 2). All seven of these brands were obtained from Irish web pages; the seed bombs were all relatively small (0.8 to 2.0 g in weight), and tended to use clay, or clay plus some soil, as the packing material. The identification of this cluster suggests that several brands may share a common source or follow similar production specifications, although we cannot confirm a common manufacturer without supply chain data.

The plant species compositions of the seed bombs obtained from non-Irish online sources (Germany; Netherlands) were very distinct from the Irish seed bombs, primarily because they contained very few native Irish plant species (Figure 2; Table 2). Two of the Irish seed bomb brands, IRE05 and IRE06, were also isolated from the main cluster of Irish brands (Figure 2). These latter brands lacked some plants that were present in most of the other Irish brands: for example, those in the families Hypericaceae, Lamiaceae, Lythraceae, and Plantaginaceae. Brand IRE05 contained some plant species that were not recorded in any other seed bombs, for example: Ranunculus acris L. and Melilotus officinalis (L.) Lam. Brand IRE06 was distinct in that it did not contain Phacelia, and was the only brand to contain seeds of foxgloves, Digitalis purpurea L.

4. Discussion

4.1. Seed Bombs: Species Composition and Prevalence of Non-Native Plant Species

The seed bombs we processed exhibited large variation in seed number, species diversity, and levels of ‘nativeness’, in terms of the proportion of species we considered as being native to Ireland. The number of species in individual seed bombs ranged from three to fifteen species, and the total number of species per brand (in five seed bombs) ranged from 8 to 24 species. These latter species numbers are very similar to those obtained by Barry and Hodge [11] for ‘wildflower’ seed mixes which contained from 8 to 25 species per packet.

Fewer than half (48%) of the total of 63 plant species we extracted from the seed bombs are considered native to Ireland. Additionally, none of the brands contained 100% native species, and in one extreme case, a brand purchased in Germany, none of the seeds were Irish natives. The value of 48% native species is similar to that reported by Barry and Hodge [11], who found that 43% of plant species in ‘wildflower’ seed mixes were native to Ireland, but is slightly higher than the 25% native species reported by Smyth [21], based on the species lists provided on the packaging. Although this situation is not ideal, at least some native Irish species were found in several brands: for example, Achillea millefolium, Caltha palustris, Leucanthemum vulgare, and Lythrum salicaria. Similarly, three of the top four most abundant seeds belonged to the native species Trifolium repens, Prunella vulgaris and Lythrum salicaria.

Phacelia tanacetifolia, the most abundant species overall, is non-native to Ireland, originating from north Central America. Phacelia is commonly included in wildflower strips, field margin plantings, and understory plantings in orchards to provide floral resources for pollinators and insects’ natural enemies, such as parasitoid wasps and hoverflies [31]. Several other species found in the seed bombs, native and non-native, are highly attractive to and/or of benefit to pollinating insects, and appear in several lists of key plant species that should be included in pollinator seed mixes: for example, Achillea millefolium, Centaurea cyanus Lythrum salicaria, Malva sylvestris, and Papaver rhoeas [31,32,33]. Many of the most frequent plant families are also considered pollinator ‘friendly’: for example, Apiaceae, Asteraceae, and Fabaceae [32,34]. So, overall, although the seed bombs did not contain only native plant species, they did contain several plant taxa that are known to be wildlife ‘friendly’ and attractive to pollinating insects.

4.2. Seed Bombs: Invasive Species, Weeds, and Anomalies

Previously, highly invasive weeds such as blackgrass (Alopecurus myosuroides Huds.) have been found in wildflower seed mixes in Ireland, which poses a serious threat to agriculture and native flora [19,35]. None of the species in the seed bombs we examined are listed on the Irish National Biodiversity Data Centre invasive plant web pages (https://invasives.ie/resources/identification-guides/; accessed on 3 October 2025) or in the recent European Union report on invasive alien species of concern [36]. However, three species we recorded are considered to be significant weeds of arable farms in Ireland (Tripleurospermum inodorum (L.) Sch.Bip., Cerastium fontanum Baumg, Papaver rhoeas L.), with six other species considered to be common weeds of vegetable crops (Achillea millefolium L., Glebionis segetum (L.) Fourr., Trifolium repens L., Prunella vulgaris L., Plantago lanceolata L., Ranunculus acris L.) [37,38].

Although it may be desirable to use seed bombs containing only native species, discovering what species seed bombs contain might not always be straightforward. We could locate species lists on packaging or online material for only 6 of the 12 seed bomb brands we investigated, which complicated the process of assigning seeds to species and identifying potential anomalies. For example, the presence of Gentiana verna L. (‘Spring Gentian’) seeds in brand IRE08 initially appeared unlikely, as G. verna is considered to be a vulnerable/threatened species in Ireland, and occurs in only a few locations in the west of the country. Nevertheless, the species was listed as present in online material for this brand of seed bombs. Without additional information, we have, therefore, assumed that our identification is correct, but that the seeds likely represent a garden variety of this plant species. Another issue concerned seeds of Arabidopsis thaliana (L.) Heynh (‘Thale Cress’), which is native to Ireland and was found in seed bomb brand IRE05, but was not present on the online species list. This indicates that an error has occurred: the species list is incomplete; we identified the seeds incorrectly; contamination occurred during the seed bomb manufacturing process; or contamination occurred when we processed the seed bombs in the laboratory. Nevertheless, for consumers, the above highlights several areas for concern. Seed bombs may not always come with a species list, and some plants will be ornamental cultivars, not wild types. Additionally, even when information on contents is provided, the seed bombs may contain species that are not listed as present, and there may be a risk that some of the plants can become nuisance weeds if sown near crops or vegetable plots.

4.3. Seed Bombs: Price and Social Value

The price of the seed bombs ranged from €3.30 to €13.50 per packet, and from €0.33 to €2.66 per seed bomb. Although variable, these prices would not generally represent a major financial outlay for small conservation projects. However, we found no correlation between the price of the seed bombs and the number of seeds and number of different species they contained. Additionally, several of the Irish seed bomb brands had very similar seed contents, casing materials, and average seed bomb weights, suggesting that these brands had come from a common source or the same manufacturer. Thus, in addition to the consideration of the nativeness and pollinator value of the plant species they contain, other caveats for buyers of seed bombs include being aware that a higher price point does not guarantee a high-quality seed bomb product, and that in many cases, cost differences may be related to packaging or re-branding, rather than the abundance, diversity, and nativeness of the plant species they contain.

Even if their ecological value is debatable, seed bombs are still associated with several aspects of human well-being. For example, as with packets of mixed wildflower seeds, seed bombs have become popular ‘eco-friendly’ gifts, wedding ‘favours’, conference promotional materials, and as promotional materials with magazines and other consumer items [11,39]. As confirmation that seed bombs are still seen as having social value, Pukorny [40] describes how in some American cities, seed bombs can be obtained from refurbished street-side candy or toy dispensers, as an eco-friendly ‘treat’. Home-made seed bombs can be used in fundraising schemes for schools and charities, and the making and planting of seed bombs can be included in educational and community programmes, enhancing social bonding and exposing students to concepts such as conservation, biodiversity, and urban wildlife [41,42]. The use of seed bombs still provides a route for the public to become involved in eco-activism, promoting a sense of civic engagement, social empowerment, and united goals when community groups successfully ‘reappropriate’ abandoned or derelict urban spaces in their local neighbourhood [24,25,43].

4.4. Seed Bombs: Recommendations

Our investigation and previous studies have clearly identified multiple issues with using seed bombs in conservation initiatives: low germination rates, low seedling establishment, low species diversity, prevalence of non-native species, presence of garden varieties, potential contamination by invasive species, lack of transparency over contents, and so on [26,27]. But the convenience and promise of seed bombs means they are still widely produced and available from online sellers. We would recommend that consumers of seed bombs undertake the following actions: (i) seek out brands that provide a species list, (ii) not be misled by labelling indicating the contents are ‘wildflowers’, (iii) be aware that seeds of non-listed species may also be present, (iv) be wary that some plant species could be significant agricultural weeds, (v) not be misled by ornate or sophisticated packaging, and know that product price may not reflect product quality, and (vi) totally avoid using seed bombs in ecologically sensitive areas. We would urge manufacturers of seed bombs to undertake the following actions: (i) always provide information on what species the seed bombs contain, and, where possible, provenance of the seed, (ii) provide information on where the seed bombs were manufactured, (iii) avoid misleading labelling (‘wildflowers’, ‘meadow species’), and consider more general alternatives, such as ’mixed flowers’ or ‘bee friendly’, (iv) if possible, provide information on expected germination rates/times, etc., and (v) provide some level of guarantee that the seed bombs do not contain highly invasive exotic plant species.

4.5. Seed Bombs: Final Words and Conclusions

As discussed above, the presence of non-native species does not necessarily imply that these plants have no value for pollinating insects and other wildlife, and there are now several reports describing the benefits of integrating exotic plants within urban planting schemes [10,39,44,45,46,47]. Some conservation organisations, such as the All-Ireland Pollinator Plan, are becoming more accepting of, and even advocating for, the use of exotic flowers and shrubs as pollen and nectar sources, especially when they offer these resources throughout the year [48,49]. There are clearly issues with the effectiveness of seed bombs [26,27,50], but the principles of restoration seed bombing are being reimagined in the form of multi-species ‘seed pelleting’, along with investigations into alternative, biodegradable casings (e.g., gelatin, alginates, starch), and inclusion of fertilisers and microbial inoculants to boost seedling establishment [51,52,53].

From the above, it would seem prudent to warn potential users of seed bombs about the inconsistencies in contents, performance, and pricing, and emphasise that their use must be avoided in ecologically sensitive areas. Primarily because of their plant species profiles, the use of seed bombs and similar wildflower seed mixes has been maligned by conservation groups, and there is a risk that continued denigration and belittling of well-meaning public initiatives will result in demotivating individuals and cessation of community conservation schemes. If we accept that the use of seed bombs is largely based on good intentions, and that some non-native plants can provide benefits to insect pollinators and other wildlife, it seems reasonable that users of these products need not be judged too harshly and should be offered guidance rather than criticism. The benefits to human well-being derived from making, receiving, and using seed bombs and the enjoyment of the wildlife-rich spaces they can create should not be overlooked. Much recent evidence indicates that even small areas of flowering plants can enhance local biodiversity, and the perceived ecological value of seed bombs may, therefore, be conditional on what comparisons are made: in highly modified urban landscapes, a few flowering plants might be considered, by default, better than no plants at all.