remove them before they flower or set seed.

-==>>>

they are both already flowering... and probably already spewing seeds from last weeks flowers..

both have certain world domination proclivities.. go out there IMMEDIATELY.. and remove ...

ken

Thanks to both of you! I spent somr time digging them up this morning.

FWIW, the shotweed's seedheads are very distinctive and there are none visible. The seedheads also take some time to ripen before they project the seeds out to a distance - the 'shot' part of shotweed. Nabbing the plants before or in bloom is perfectly adequate,

And feel free to overlook the hyperbole in the previous comment :-)

We had a ton of flickweed (a common name of the white-flowered one) in the nursery I worked at. It set seeds so quickly. But it's easy to pull out if you keep on top of it. If it is left, it would grow very quickly indeed and then become a pain to remove

It flicks its seeds when you touch the plant if the seeds are ripe. So it's important to pull it out before the seeds appear. A colleague of mine got a seed in her eye and had to go to hospital to have the seed removed. I was a bit aghast.

Yikes! Your poor colleague!