ADVENTIVES AND ALIENS: Adventives & Aliens News 22
ADVENTIVES AND ALIENS Adventives and Aliens News 22 COMPILED BY MATTHEW BERRY
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promised a longer preamble last time and here one is – unavoidably a miscellany of odds and ends that have accumulated over a considerable period, though none of them out of date as such. It is easy to forget that non-native plant species which have become so familiar in some parts of Britain and Ireland that they barely register as aliens any longer, have only recently arrived in others and are spreading detectably in many more. Graeme Kay, VCR for Cheshire, provided the following illuminating statistic for Polypogon viridis (Water Bent) in v.c. 58, where it was first recorded in 2006. As of 2019 it was known in 55 sites, some harbouring established populations. He describes it as ‘spreading faster than any previous species’. A botanist just now starting to explore urban habitats in certain southern vice-counties will be already too late on the scene to observe this rapid spread first hand. Graeme Kay also reminded me of the v.c. 58 site for Mentha cervina (Hart’s Pennyroyal), the species that was recently discovered by Ambroise Baker at South Gare (v.c. 62). The Cheshire record was featured in Adventives & Aliens News 5 (with photos), where I erroneously gave the location as Chorley. It should be Chorlton (my apologies). It was certainly still present there in 2019, indeed Graeme described it as ‘thriving’. Adventives & Aliens News 20 contained a v.c. 58 record of Caltha palustris subsp. polypetala. This is the name often applied to large-leaved, largeflowered (and perhaps also flore pleno) garden forms of C. palustris (although Stace [2019] only mentions var. barthei in relation to them). However, Rodney Burton explained to me that strictly speaking the name C. palustris subsp. polypetala refers to a quite different plant, a native of the Caucasus and Asia Minor (plus Bulgaria and Iran), which normally
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BSBI NEWS 146 | January 2021
has flowers with seven, relatively narrow perianth segments. It is presumably almost unknown as a garden plant in Britain and Ireland. He also writes about this matter in Wild Flower Magazine Autumn 2020 (No. 513), on p. 18. Every year I check the constituents of ‘wild flower seed mixtures’ sown in parks and gardens around Eastbourne, to see what might turn up later in recordable spots in gutters, pavement cracks and at the bases of walls, etc. This year Iberis amara (Wild Candytuft) was a feature of a number of them for the first time. The chalky soils and relatively Mediterranean local climate (even if it is not strictly a Mediterranean plant) might be to the species’ liking, although I have only ever seen I. umbellata (Garden Candytuft) before. Indeed non-native records of I. amara seem to be rare generally. While it might struggle to rival its (usually) pink-flowered congener for number of casual occurrences, it will certainly never compete with that other white-flowered annual crucifer, Lobularia maritima (Sweet Alison), a very frequent street weed in Eastbourne. Having the information to hand, a few more updates are in order. Colin Pope observed that Pelargonium inodorum (Scentless Geranium) was still present at its v.c. 10 site in 2020 and that it even appeared to be spreading (see BSBI News 131: 54). Is it present elsewhere? Calepina irregularis (White Ballmustard) could not be detected at its Southampton (v.c. 11) site in 2015, the year after its discovery there (see Adventives & Aliens News 6). Nor has it been observed since. In October 2020, George Hounsome and Eric Clement found c. 40 plants of Bidens frondosa (Beggarticks) surviving at the head of a now badly overgrown ditch at Elson, Gosport (v.c. 11), where it was first recorded in 2010 (see Adventives & Aliens News 4). Is it more generally
