Just give a crack and watch out.

An aggressive weed found in open areas, lawns, fields
and waste areas. Introduced from Eurasia it is now
found throughout most of the United States. It grows
4"-16" tall with weak stems that branch at the base.
The upper (and for the most part lower) leaves are
typically rounded and sessile with coarsely toothed
margins. Flowers arise at the leaf axils. Mint family.