I had some blanket flowers in pots that had died last fall. Something began growing in the pots and it managed to survive the winter and is still doing good. I am in N. Texas btw. The plant has 1/2 inch deep red berries that grow from fairly inconspicuous flowers. In the picture the flowers are about 1/4 inch and the berries are 1/2 inch to give a size reference.
Pokeweed, Phytolacca sp.- In Texas should be Phytolacca americana, unless you accidentally got seed from a cultivated variety.