United Kingdom 
hi there!
we planted the flowers behind the brown stalk plant about a month ago, we woke up two days ago to find this brown stalk plant had shot up within hours! when touched or moved it releases a smoke like vapor from the top bud, only a small amount. the bed has not been used for years and we have only just moved in, wanting to make it look alive. it has been under a plastic sheet for a while. this little lovely has just popped up and we would like to know what exactly it is?
many thanks
mark
26 Mar, 2011
Answers
Yes I think it is a toadstool too- one called stink....... something or other that smells unpleasant.
27 Mar, 2011
This is the reproductive head of Equisetum arvense (unfortunately for you!).
The underground rhizomes (stems) can go down for many feet and it is a sod to get rid of. There will be feathery branched stems appearing later.
27 Mar, 2011
Hmmm...would glyphosphate work if Lines cut off the stem and put a couple drops of concentrate on the fresh surface?
28 Mar, 2011
Supposed to work better later in the season when the plant is about to die back for winter.
29 Mar, 2011
Ah! It works that way with weedy sedges, here.
30 Mar, 2011
It's a little hard to see, but it looks like a toadstool of some kind. Most are harmless to plants or people--though not good to eat--but may be a symptom of an underlying problem.
27 Mar, 2011