BSBINews103

Aliens - Bassia scoparia and its viatica1 status / Senecio inaequidens, the numbers 35The results (Kitchener, 2006) indicated thatBassia scoparia has already crept up on usunawares, as it were, and has a significantpresence on Kentish roads. It may now befound along the A2 from Dartford Heath tobeyond Gravesend (15km), in at least 8 lkmsquares. In most cases these are single plants orsmall groups, but there is a large population bythe sliproad to the Bluewater shopping centre,lining the road continuously. It is also presenton the M20 near Maidstone, at the Leybourne,Ay1eford, Sandling and Detling junctions.From the Sand1ing junction it runs northwardsalong the A229 to Blue Bell Hill. From theDetling junction, where there is a population ofseveral hundred plants, it runs north-east alongthe A249 to Detling Hill and then appears 9kmfurther on, at the junction of the A249 with theM2. There are now 19 lkm squares withinwhich roadside Bassia scoparia has beenrecorded in 2004/05, in v.cc. 15 and 16.While it is possible to survey by car at speed,with the precaution of disregarding abundantbushy Atriplex littoralis (which I recorded ascommon on the A2 as far back as 1982), thisinvestigation was carried out on foot. Undoubted1ythis enabled identification of occasionalplants which would not have been conspicuousenough otherwise. On the other hand, survey onfoot will have under-recorded as regards thoseareas that could only be accessed with binoculars- motorways and the A2 centre reservation.The plant's colonization abilities reflect studiesby Stepphun & Wall (1993) which show germinationas occurring in severely saline conditions,particularly when well watered. Thehighway habitats provide both that salinity,which otherwise limits competition, and water,through vehicle spray and highway drainage.As regards the tumb1eweed characteristic ofBassia, it is sometimes described as beinguprooted by wind, but the dead plants willreadily snap off at ground level, leaving the baseand roots behind, as can by verified by walkingthrough a group of them.ReferencesKITCHENER, G.D. 2006. Bassia scoparia (L.) Voss.Bulletin of the Kent Field Club 51: 81-84.STEPPHUN, H. & WALL, K. 1993. Kochia scopariaemergence from saline soil under various waterregimes. J. Range Manage. (Nov. 1993) 46533-53.Senecio inaequidens, the numbersQUENTIN GROOM, Louis Pelserssquare 1, 3080 Tervuren, Belgium. qgroom@reticu1e.co.ukI wrote in the previous BSBI News (Apri12006) Since 2000, S. inaequidens has been found atabout the spread of Senecio inaequidens 60 sites, mainly in the south of England. This(Narrow-leaved Ragwort) across Europe. I compares to 35 sites between 1987 and 1999gave little proof for a UK invasion, but now I and 15 sites before 1987. Despite the ratherhave gathered some evidence to back up my rough estimates of population sizes given byassertion. Having written to the recorders in the recorders, I have made guesses at the numbersvice-counties where S. inaequidens has been of plants in Britain. The current population is,recorded, I have made estimates of the numbers at very least, 300 plants, but more likely aboutof sites and plants in the UK.1500 plants. If there are still unfound sites, thenSingle plants crop up by roadsides and in these would add to the numbers.pavement cracks, these plants often disappear The turn of the millennium has shown aafter a year or two. However, in several places marked change in fortunes for Britishlarge popu1ations have established, particularly S. inaequidens. Overall, its numbers are stillon demolition sites. These established popu1a- small, but the rate of population growth istions are often in port towns such as Plymouth, impressive. S. inaequidens is not the mostSouthampton and Felixstowe. By far the largest odious of alien species, but it can be a weed ofnumbers of sites are in eastern London, particu- agriculture and will invade some naturallady in the vice-counties of West Kent (v.c. 16) habitats. If we want to stop its spread, it mightand South Essex (v.c. 18). From this distribution still be possible. However, it seems likely thatof sites, I suspect that multiple introductions another Senecio is coming to a town near you.have occurred, probably hitchhiking on vehicles Many thanks to all those people whocrossing the channel.responded to my request for information.