Germination

• Plant milkweed seeds in flats containing light, sandy, well-draining soil four to eight weeks before the last frost. Before sowing the seeds, thoroughly water the soil and let the excess water drain out. Sow the seeds 1/4 to 1/2 an inch apart and 1/4 inch deep. Cover the flats with clear plastic and place under a grow light. The seeds should germinate within five to seven days.
  
  

Transplanting

• When the milkweed seedlings are between 4 and 6 inches tall, they are ready for the outdoors. Acclimate the seedlings to their new environment by placing them outdoors for a few hours a day for one to two weeks. After the risk of frost is over, transplant them to the garden. Space milkweed transplants 6 to 24 inches apart, depending on the species. Keep the transplants well-watered until they are established. Place mulch around the transplants to retain water and reduce weeds.
  
  

Fertilizing

• As seedlings, fertilize milkweeds two or three times during their growing season with a water-soluble fertilizer. After the plant is established, it needs little to no fertilizing.
  
  

Light

• Milkweed prefers full sun, and without sufficient light the flower will not bloom. Milkweed tolerates a substantial amount of heat, but high levels of humidity make the plant susceptible to powdery mildew.
  
  

Pests and Diseases

• Milkweeds are host plants for monarch butterflies and the leaves will be eaten by the larvae. Don't worry about the disappearing foliage. It will grow back quickly, and when the caterpillars morph into butterflies, the milkweed provides nectar for the butterflies. Aphids are a bigger nuisance to the milkweed and infestations can occur quickly. Aphids suck the plant juices, creating white flecks on the leaves. Aphids also secret honey dew, which attracts ants and can grow fungi. Control aphids with insecticidal soaps or horticultural oil. Powdery mildew is another common milkweed problem and is recognized by a whitish-gray powdery substance on the leaves and stems. Remove infected plant areas and reduce relative humidity around the plant.
  
  

Irrigation

• Milkweed is a fairly drought-tolerant perennial, except for the swamp milkweed species, which grows best in constantly moist conditions. However, the plant can withstand high levels of water and frequent rainfall should not disturb the plant. Wait until the soil is dry or the leaves are just starting to wilt before watering.