"Mad Cow" wrote

Himalayan balsam may be waist-high or it may be over three metres tall
with stems as thick at your wrist - that's enormous for an annual. It
can blanket whole floodplains. Animals won't eat it.

It usually arrives as a seed: it floats down rivers, lurks in the mud on
walkers' boots, is carefully brought home by children to surprise you by
popping the pods.
If you find it on your patch, don't let it seed. Pull it up and compost
it. If you've bought a place with a lot of it, check your government's
advice on the best way to get rid of it.
[

An obnoxious (but pretty) weed of waterways in our part of the UK together
with a couple of smaller species (yellow) I've seen which are not so
invasive. It grows so quickly it shades out and outcompetes all other wild
plants causing serious loss of habitat for local wildlife.
--
Regards. Bob Hobden.
Posted to this Newsgroup from the W of London, UK