If starting seeds outdoors isn’t practical, you can also do it indoors in late winter or early spring.
You can start planting outdoors after all danger of frost has passed. Be gentle with plant roots and disturb them as little as possible.
How to Grow Butterfly Weed
As far as garden design goes, you’ll definitely want to plant butterfly weed where you’ll see it often so that you can enjoy the butterflies that flock to it.
Starting butterfly weed from seed in the fall is the best growing method. As mentioned, the plants do not like to be moved, so sowing the seeds where you want the plants to grow is the best solution.
You may also see black and orange milkweed bugs (Oncopeltus fasciatus) on your plants. They do feed on the leaves, stems, and seeds of different types of milkweeds, but rarely do enough damage to harm the plants.
Leave the bucket outdoors for two or three days to let the fluff blow away. Stir the seeds occasionally to loosen more fluff. Do not worry if some of the fluff remains, since it won’t inhibit the germination process.
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.
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.
Before you begin to harvest the butterfly weed pods, sterilize your cutting tools. Dip the blades into a full-strength household cleanser, such as Lysol or Pine-Sol. Repeat between cuts to prevent the spread of diseases.
Water the butterfly weed seeds whenever the compost feels barely damp when pressed. Apply the water by the spoonful or use a spray bottle to keep from dislodging the seeds.