Ptyxis Ecology - Our Botany Blog

Monday, 25 October 2010

New things to look out for in the autumn

Quentin Groom sends the following pictures and text about Conyzas:

Conyza canadensis (Canadian Fleabane) first established in the North-east in the 1990s and is now well established in Newcastle, Gateshead and Hexham.

Close-up of C. canadensis infloresence.

Its taller, hairy cousin C. sumatrensis (Guernsey Fleabane) has become established around the station in Newcastle over the past two years.

Both look similar, but C. sumatrensis is distinguished by having much hairier flower heads and a distinctly cone-shaped inflorescence. C. canadensis has hairless or slightly hairy flower heads and a columnar inflorescence. The shape of the inflorescence is a difficult character to grasp, until you have seen it in the field. However, once you’ve got used to it, it allows you to spot each species at a distance.

Both species are urbanophytes and they grow in pavement cracks, walls, gutters and other microhabitats of the urban landscape. They are expected to increase!


PS. I first started botanising seriously when I lived in London in the late 1990's. By that time C. sumatrensis had become probably the most common plant in Central London even though it had not been recorded at all when Rodney Burton's 'Flora of the London Area' was published in 1983.




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