How to Grow Asclepias Tuberosa

Scatter seeds on the surface of well-drained soil in a full-sun location. Gently rake to cover with 1/16 inch of soil. Keep the seed bed moist until germination occurs, which can take four weeks or more. Pull any weeds that sprout in the flower bed and seedlings that are too close together -- at maturity the plants are 18 to 24 inches tall and wide.

Check soil for dryness before watering once plants are established, meaning they have three or more sets of leaves. Over watering will promote fungal infection, or rot the roots, as butterfly weed is drought resistant.

Watch for aphids on the plants leaves or stems. Aphids are very small insects which usually will cluster near the tips of the stems, or on the buds. They are usually green, but can be black or orange. Aphids can be blasted away with water from the hose, or killed with insecticidal spray. Avoid pesticides, though, if you're growing the plants to attract butterflies.

Deadhead spent flowers to encourage new blooms by clipping off the flower cluster at the bottom of the stem. Cutting back the plant's stems can also encourage bushier growth.

Fertilize infrequently, as the butterfly weed does best in poor soil. You can spread an all-purpose fertilizer around the plant in early spring, following package direction for correct application.