A little known fact is that monarch caterpillars feed only on milkweed species. Other plants can provide nectar for the adult butterflies, but without butterfly weed and other varieties of milkweed, the caterpillars can’t survive.
The seeds need the cold period of winter in order to germinate in the spring. You can sow them directly into your garden in late fall (usually November).
Benefits of Butterfly Weed
If you want more plants around your garden, collect the seeds as they ripen and lay them down in the fall in the area(s) you want new plants.
Butterfly weed blooms with bright orange flowers that are attractive to butterflies and humans alike. It’s an easy-to-grow and beautiful plant to add to your garden.
After you have your pots filled, sow one or two seeds in each pot. Start seeds 6-8 weeks before your last average frost date.
Place the butterfly weed seeds in a plastic bag filled with 1 cup of moistened perlite. Store the bag inside the refrigerator for three months. Mist the perlite with water every few days to keep it from drying out completely.
Sometimes called pleurisy root, butterfly weed (Asclepias tuberosa) is a perennial wildflower grown for its showy, reddish-orange flower clusters and textured, lanceolate leaves. A member of the milkweed family, it thrives throughout U.S. Department of Agriculture plant hardiness zones 3 to 9, where it is frequently added to butterfly gardens and native plant landscaping.
Transplant the butterfly weed into a permanent bed in spring just after the last frost. If planting butterfly weed in clay soil, dig in 2 to 4 inches of compost to lighten the soil, or consider building raised beds to increase drainage.
Prepare peat or other biodegradable pots before removing the butterfly weed seeds from the refrigerator. Fill 3-inch starter pots with a mixture of half seed-starting compost and half coarse sand. Moisten the mix and press it firm.
Arrange the starter pots on a propagation mat near a source of bright, indirect light such as near a partly shaded south-facing window. Set the temperature on the propagation mat to 86 F during the day. Turn it off at night.
Watch for germination in two to three weeks. Turn off the propagation mat one week after the seeds sprout. Move the pots into a cold frame outdoors or against a south-facing wall with noonday shade.
Make a 1/4-inch-deep planting hole in the center of compost mixture. Drop one butterfly weed seed in the planting hole. Cover it with a loose layer of compost. Mist the compost to settle it.