I am wondering what this plant is that practically "popped up" in my backyard. It's growing in mostly clay soil with some compost on the side. It grew from nothing to about 3' tall in a matter of 4-5 weeks. It gets about 6 hours of sun from morning (9am?) 'til around 3pm, and is in the midst of some volunteer cherry tomato plants. The leaves are smooth underneath, and are spaced in thirds(?) around the plant (if that makes sense). The stalk is about 1" thick. And I am concerned that it might be poisonous. But, it's a healthy plant and if it happens to be a good plant, I'd keep it around. I think it's an annual, as it doesn't look hardy. Thanks for your time.

Gardenz4evr