How to Grow Butterfly Weed (Asclepias)

Low-maintenance and undemanding, butterfly weed (Asclepias tuberosa) is a familiar native throughout much of the U.S. Dotting summer roadsides and rocky slopes with brilliant, tangerine-orange flowers, this carefree perennial moves into cultivated gardens with the same ease. As its name suggests, butterfly weed provides an important food source for several butterfly species, including monarchs. Sometimes called butterfly milkweed in a nod to its plant family, butterfly weed has none of its relatives' milky sap.

The natural habitat chosen by wild butterfly weed reflects growing conditions that suit this plant best. Dry, fast-draining, sandy or rocky soil provides a welcoming spot for its tuberous roots. Butterfly weed even handles the caliche hardpans of the Southwest. The plant tolerates partial shade, but full, direct sun encourages profuse, long-lasting blooms. Flat-topped flower clusters measure up to 5 inches across, and ornamental seed pods up to 6 inches long follow the blooms in fall. Plant butterfly weed where you can watch their winged visitors and enjoy the blooms and pods, in your garden and in fresh or dried bouquets.

Mature butterfly weed grows up to 2 1/2 feet tall and 1 1/2 feet wide. Each year, the clump grows more dense, multiplying its numerous stems. Space plants at 2-foot intervals to allow for growth. Aphids may trouble butterfly weed planted in close quarters with garden plants of similar height, so don't overcrowd. Beneficial ladybugs make quick work of the aphids, as does a strong blast from the garden hose. Low, mounding butterfly weed spreads slowly, but spread it will. Remove seedpods before they burst unless you want more butterfly weed. The plants take two to three years to bloom from seed. If room allows, butterfly weed naturalizes readily, blanketing summer scenes in orange.

Established butterfly weed adapts to dry or moist conditions, but these highly drought-tolerant plants do best with minimal to no supplemental water. Let natural rainfall provide the plant's moisture needs, except in the most extreme drought. If you water, do it deeply and infrequently, and check the soil by hand. Let it dry well before you water again. In overly wet or poorly drained sites, butterfly weed suffers from crown and root rots. Poor, infertile soil supports luxurious butterfly weed blossoms without any added fertilizers. Keep high-nitrogen fertilizers, including lawn products, away from butterfly weed or you may limit their vibrant blooms.

Butterfly weed grows in U.S. Department of Agriculture plant hardiness zones 3 through 9. The plant dies to the ground each winter, and then sprouts from its tubers in spring. While other flowers jump into action, butterfly weed takes it slowly. Leave the dead stems standing over winter, or mark the plant's place in fall so you know where to find it in spring. Butterfly weed's long taproot can extend 12 inches or more. Once established, these long-lived beauties don't like to be disturbed. All butterfly weed parts can be toxic when eaten by humans or animals, but the same toxins make monarch caterpillars unpalatable to predators.