That was my first thought too, milkweed! I would be pleased to have milkweed on my property. I was looking into planting some for the monarchs, as monarchs are down 90% in N.C .. I'm just hoping it's not dogbane, Dogbane looks very similar to milkweed . I just don't know enough to determine without seeing the flower and/or seed pods. If it is milkweed I was thinking it either common or purple milkweed.