Lawn, spreading for the past few years from a flower bed. I think these were mistakenly introduced in some soil we bought, along with some invasive dayflowers (I think Commelina benghalensis) that are trying to take over.
Stipules measured up to 1.5 mm. Entire plant was glabrous.
Volunteer near a compost pile, not planted. Either Cucurbita pepo or Cucurbita melopepo var. melopepo according to Weakley's key, although it would seem I need to wait for the fruit to develop tell which one it is. Any gourd experts out there who can tell the species without the fruit?
Update 2024-06-27: Added some images of the fruit as evidence. The fruit measured about 7cm long and 13cm in circumference (around the widest point)