In article , martin
writes
Having read all the stuff about the unintentional spread of GM
plants, and seen giant hog weed growing along miles of grass verges,
how can you be careful not to let it escape?

Make sure it doesn't set seed.

Why does it appear some
years and not others?

--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/edward/index.htm