Asclepias tuberosa, known as butterfly weed or butterfly milkweed, grows throughout the southern and southeastern parts of the United States, often in the dry soil along roadsides. It may also be planted in areas along the west coast. As its common name suggests, its orange, red and yellow flower clusters attract butterflies, especially monarchs. Eating its roots raw is purportedly good for bronchial ailments, gas and hemorrhaging.
Plant butterfly weed in a location that offers exposure to full sun or at least partial shade. You can plant it in almost any soil, be it dry, acidic, clay, sandy, dry, loamy or humus-rich, but avoid heavy soils. Ensure soil is free of salinity, as butterfly weed's salt tolerance is poor.
Choose a location you can leave undisturbed year round to avoid damaging the the plant's delicate crown when it's dormant and hard to see.
The taproot of butterfly weed makes it difficult to transplant seedlings. If you plant indoors, use a biodegradable pot that you won't need to pull the plant out of to transplant.
Butterfly weed is slow to germinate, requiring three to four weeks at 70 to 75 degrees Fahrenheit. In zone 7, this means you should plant in June or July. In zone 8, planting may take place between May and August. In zone 9, that range expands to March through September. Zone 10 gardeners can plant in any month of the year but January.
Grow butterfly weed at a separation distance of 18 to 24 inches.
Butterfly weed may self-seed each year. Depending on how much of the plant you want in your garden, this may be a boon or an invasive curse. Be aware of butterfly weed's potential to escape into the landscape.
Fresh butterfly weed seeds may need to be chilled to speed germination. You can do this easily by the traditional means of planting in a cold frame in the chilly months of early spring or late fall. A more modern approach involves sowing the seed in moistened compost, sealing it inside a polythene bag, letting it sit at 60 to 65 degrees Fahrenheit for three days, then putting the bag in the refrigerator for the rest of the chilling period. When using this method, ensure the bag contains sufficient air and that the compost is neither too dry nor too wet. The seeds need to be moist, but standing water will injure them.