I had the same thing happen in my boyfriend's backyard. One day in early to mid winter we had to get rid of a plate of seeds..so we chunked them in the yard. Come Spring we noticed these little plants starting to grow. Once we got a look at the leaves we knew undoubtedly what it was. It killed us to do it, but we had to kill them. Not something you want in your backyard when you live in a busy city like Arlington. Would've been great to let them grow and harvest.

Definitely post pics!!

<3