Tweedside alien plants

Abstract

Commentary: Douglas McKean* The woollen industry allowed alien seeds to escape via effluent from the mills on to the banks of the Rivers Gala and Tweed. The old skin works in Galashiels was another source of alien seeds and wool shoddy (with lurking alien seed) was spread on fields to improve soil fertility. Modern effluent treatment and the cessation of spreading wool shoddy has largely curtailed the introduction of alien seed except for those introduced via wild bird seed which comes from anywhere with a cheap source of seed even as far away as America. Most of us would be unaware of this but for the telltale plants such as the American Ragweeds, e.g. Ambrosia artemisiifolia L. (annual), which spring up around bird feeders. This alien plant, along with Phacelia tanacetifolia Benth. is the one most often sent to the Botanic Garden for identification. Fortunately, neither is aggressive coloniser, at least not in our climate, and so they do not prosper like the Japanese Knotweed (Fallopia japonica Houtt.) or Giant Hogweed (Heracleum mantegazzianum Sommier & Levier). Ambrosia psylostachya DC., a perennial, has however become established in Ayrshire and S. and W. Lancashire. Incidentally, the annual Ragweed is hyper-allergenic and causes severe hay fever; its control is compulsory in many countries in continental Europe where the species has become widely established. The paper by Hayward is a good illustration of the effects of industry on botanical diversity, albeit temporary in most cases. There is currently an upsurge in interest in non-native species (e.g. Manchester & Bullock 2000). A recently published government consultation on the subject can be found at: http://www. defra.gov.uk/wildlife-countryside/non-native/index.htm