On a riverside walk in the Lothians last week, we found a plant in full bloom with creamy green flowers that we recognised as being Tellima grandiflora (Pursh) Douglas ex Lindl. ‘Fringe cups’. Walking on further, we found a mass of other plants with similar habit, but with flowers that were still in bud. The leaf shapes were a bit different, but not strikingly so at first glance. Were they also Tellima or were they something else? – perhaps Tolmiea menziesii (Pursh) Torr. & A.Gray which is known as ‘Pick-a-back plant’ or ‘Mother of thousands’.
Both these species are members of the Saxifragaceae and arrived in the UK as horticultural introductions from western North America, which have since become naturalised here. Tellima was in cultivation in the UK by 1826 (Don, PN et al., and Donn J, 1845), and was first recorded in the wild in 1908, while Tolmiea was introduced in 1812 and first recorded in the wild in 1928 (BRC). Tolmiea sprouts new plantlets at the junction of petiole and leaf, producing dense carpets of one clone, reflecting its English names, and rarely sets seed, whereas Tellima does not produce plantlets but does set seed. The Royal Horticultural Society (RHS) web site tells us that Tolmiea is semi-evergreen and Tellima is deciduous.
Illustrations in various floras showed that Tellima and Tolmiea are superficially similar at the vegetative stage, so we decided to investigate further, hoping meanwhile that we would find some flowers open on the questionable plants. The flowers are distinctive: Tellima flowers are actinomorphic (radially symmetrical) greenish, with pink or red tinges, a bell-shaped hypanthium and have 5 sepals and 5 petals which are broad and fringed, while Tolmiea flowers are zygomorphic (bilaterally symmetrical), brownish-red with five sepals, but only 4(-5) petals and a narrow, tubular hypanthium (Stace, 2019).
Both species, with flowering shoots extended and flowers in bud. Tellima grandiflora (left) and Tolmiea menziesii (right). Photos: © Chris Jeffree
Leaf shape: The leaves of Tellima (left) are rounder in outline with more rounded lobes. Those of Tolmiea (right) are more triangular with more pointed lobes. The stem leaves of Tellima are almost sessile, while those of Tolmiea have long petioles. Photos: © Chris Jeffree
Flowers in bud. The young inflorescence of Tellima (left) is drooping, while that of Tolmiea (right) is erect. Photos: © Chris Jeffree
Tellima flowers are actinomorphic (radially symmetrical) with five sepals and petals mounted on an inflated hypanthium. The u-shaped surface in the floor of the hypanthium secretes nectar. Photos: © Chris Jeffree
Tolmiea flowers are zygomorphic (bilaterally symmetrical) with five sepals and usually four very narrow petals. Photos: © Chris Jeffree
Like many other species introduced by the horticultural trade, they have both spread into the wild (see maps below). BSBI records show that Tolmiea and Tellima were represented by 444 and 445 records respectively before 1987. Since then, the spread of Tellima has outpaced that of Tolmiea so that there are 4489 records of Tellima and 2277 records of Tolmiea dating from 1987 onwards. Both species are widely available for purchase, and while Tellima has the more showy flowers, Tolmiea has the novelty of producing baby plants in its leaf axils.
An early record of Tolmiea being sold in the nursery trade can be found in the 1889-90 catalogue of the Orcutt Seed and Plant Company San Diego, California, which advertises Tolmiea menziesii to the trade at 5$ per 100 plants.
The distribution of Tellima grandiflora in Britain and Ireland before 1987 and from 1987 onwards ©BSBI 2022
The distribution of Tolmiea menziesii in Britain and Ireland before 1987 and from 1987 onwards ©BSBI 2022
An intriguing aspect of Tolmiea menziesii is that it is a polyploid species, with 2n = 14 and 28 chromosomes in the diploid and tetraploid cytotypes in its native range in NW America (Visger et al. 2016) where they grow in coastal understoreys of the Pacific Northwest. The niches of these cytotypes barely overlap: the diploid occurs in California and southern Oregon, while the tetraploid is more northerly, occurring in northern Oregon, Washington and British Columbia.
Tolmiea menziesii was initially recognised as a single taxonomic species with both diploid (2n = 14) and autotetraploid populations (2n = 28) (Soltis, 1984). However Judd et al. (2007) present a body of evidence and wide-ranging arguments that the diploid should be considered a distinct species, named Tolmiea diplomenziesii, which is now an accepted species, formally named Tolmiea diplomenziesii Judd, Soltis & P.S.Soltis (POWO, 2022). The tetraploid should retain the name Tolmiea menziesii as the original collection of the species by Archibald Menzies was from north of Vancouver, within the range of the tetraploid. Morphologically, the diploid has a smaller stature and subtly different characters of the basal rosette and stem leaves.
The distributions of Tellima and Tolmiea overlap in their native range, and here in the UK too. While Tolmiea has 14 or 28 chromosomes, Tellima has 2n = 14. Weiblen and Brehm (1996), report hybrids between the two species in their native range with 2n = 14 or 21 chromosomes depending on their proximity to either T. menziesii or T. diplomenziesii. Tellima was the successful maternal parent in Tolmiea x Tellima crosses. Like Tolmiea, the hybrids possess vegetative plantlets. Many other features, including the floral characters, were intermediate between the two parents, and the flowers were ‘nearly actinomorphic’.
The Biological Records Centre entry for T. menziesii says that it is not known whether our plants in the UK are diploid or tetraploid. Both cytotypes may have been imported at various times. We have not done any tests on our local plants, but comparing the drawings of the diploid in Judd et al. (2007) with our observations, their general appearance suggests our local plants are probably the tetraploid. Perhaps there are diploids elsewhere in the UK, however Visger et al. (2016) conducted ecological niche modelling of the cytotypes across their range in North America and extended this modelling to assess the potential situation in Britain, Visger (pers comm.) tells me that they did not expect the British climate to be suitable for the diploid.
Perhaps hybrids between the species occur here too. Flow cytometry or chromosome counts on a range of samples would quickly sort which cytotypes occur here, and the presence or absence of hybrids. Now is a good time of year to look out for intermediate flowers. This study would make a great student project!
So, to answer the question in the title, there are definitely two species growing in the UK – Tellima grandiflora and Tolmiea menziesii. Tolmeia diplomenziesii is unlikely to grow here, but there could be Tellima x Tolmeia hybrids.
References
BRC Biological Records Centre Online Atlas of the British and Irish Flora https://plantatlas.brc.ac.uk/
BSBI Botanical Society of Britain and Ireland https://bsbi.org/maps
Don, PN et al., and Donn J 1845 Hortus cantabrigiensis : or, An accented catalogue of indigenous and exotic plants cultivated in the Cambridge Botanic Garden, publ. London, Longman. https://doi.org/10.5962/bhl.title.160219
Judd, WS, Soltis DE, Soltis PS, and Gretchen II 2007 Tolmiea diplomenziesii: A new species from the Pacific Northwest and the diploid sister taxon of the autotetraploid T. menziesii (Saxifragaceae). Brittonia, 59(3), 2007, pp. 217-225. https://www.researchgate.net/publication/225326207_Tolmiea_diplomenziesii_A_new_species_from_the_Pacific_Northwest_and_the_diploid_sister_taxon_of_the_autotetraploid_T_menziesii_Saxifragaceae
Orcutt Seed and Plant Company : trade price list 1889-1890 https://www.biodiversitylibrary.org/page/45346254#page/6/mode/1up https://doi.org/10.5962/bhl.title.85241
POWO (2022). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/
Retrieved 01 May 2022.
RHS Royal Horticultural Society https://www.rhs.org.uk/plants/
Soltis, DE 1984. Autopolyploidy in Tolmiea menziesii (Saxifragaceae). American Journal of Botany 71: 1171-1174.
Stace, CA 2019 New Flora of the British Isles (fourth edition). C&M Floristics, Suffolk.
Visger CJ, Aubrey CC, Patel M, Sessa EB, Soltis PS and Soltis DE 2016 Niche divergence between diploid and autotetraploid Tolmiea. American Journal of Botany 103 (8): 1396 – 1406. doi:10.3732/ajb.1600130
Weiblen, GD and Brehm, BG (1996) Reproductive strategies and barriers to hybridization between Tellima grandiflora and Tolmiea menziesii (Saxifragaceae). American Journal of Botany 83(7): 910-918. 1996.
© Julia Wilson and Chris Jeffree
Botany in Scotland 