You can sow butterfly weed seeds directly in the garden. In fact, direct sowing is preferable to starting indoors because butterfly weed–a perennial with orange or red flowers–has a long tap root that doesn’t transplant well.
Butterfly weed thrives in an average, well-drained soil in full sun. The plants are drought tolerant and grow well in a dry soil. Plant the seeds 1/16 inch deep in spring. Seedlings are slow to emerge–mark the spot so you won’t forget where you planted them.
Leave the faded flowers on the plant to encourage the production of seed pods. Each seed pod releases a hundred or more seeds, some of which will fall to the ground and produce new plants in spring.
In fall, butterfly weed seed pods pop open to release seeds. Each seed is equipped with long threads that catch the wind, carrying the seed to other areas.