I am anxious to hear an answer to this. I thought it was Queen Ann's lace but my daughter said it wasn't, another response was poison hemlock I hope someone comes up with the true answer. I know the seed is a catchon to clothing

I didn't know. But it looks like the message posted here, after yours, "Hedge Parsley (Torilis Arvensis) aka beggars lice", is asking about the same plant. Most of the Umbellifers don't have bur-like seeds. (First one I have heard of.)

Don't know what the odds are re the posts here, but you might want to investigate this plant. May be it.

Poison hemlock seems plausible, looking at images of it. I don't think it's hedge parsely / beggar's lice - the images of those look noticeably different.

Guess I shouldn't eat it or feed it to animals just in case.

I haven't noticed it sticking to clothes.

Are the flowers and foliage behind them from the same plants?

The leaves in the picture are from a different plant, but the weed does have leaves as well. When it first springs up the flowers aren't visible at all and it looks much different.

Also the stalk looks like celery.