Milkweeds die back to the ground at the end of the growing season or at the first frost. These plants are considered invasive and spread very quickly. It’s important to keep them pruned back to avoid them taking over. In their native habitat, they grow rampant along sides of roads, fences, in fields, and pastures in areas with full sun and very little shade. Most garden plants typically last up to 7 years, whereas Milkweeds live as long as 20 years.