For a garden fluttering with brilliant orange and black monarch butterflies, consider growing one of the few plants the insects use to host their eggs -- the aptly named butterfly weed (Asclepis tuberosa). This native perennial, suitable for U.S. Department of Agriculture plant hardiness zones 3 through 9, is hard to find as a transplant because of its long, delicate taproot and is best started from seed. While you can start the plant indoors in the fall or spring, the finicky seeds then need lengthy pre-chilling in the fridge or frequent temperature manipulation to sprout. Save time, frustration -- and fridge space -- by simply sowing butterfly weed seed outdoors in the fall.
1 Clear an area of the garden in full sun that drains well in late summer to early fall. Butterfly weed is not picky about its soil as long as it is fairly dry, and the plant can thrive in nutrient-poor, rocky or sandy soil.
2 Spread a 1- to 2-inch layer of compost over the area, and dig it in a few inches deep to lighten the soil and loosen it for seeding. Break up any clumps, and rake the surface of the seed bed smooth with a garden rake.
3 Sow mature, fresh seed harvested from butterfly weed pods, or stored or purchased seed up to eight weeks before your first expected frost. If you harvest your own seed, pick pods when they turn from green to tan, but before they split open and the seed blows away. Cover the seeds to four times their depth.
4 Mark the area where seeds are planted with a stake or other marker.
5 Water the seeds well, and keep them moist beginning in the early spring after the three-month cold period -- called stratification -- has passed. Avoid letting the seed bed dry out during the 15 to 20 days the seeds take to germinate and emerge. Increase time between watering as the plants begin to grow until you let at least the top inch of soil dry before watering again.
6 Thin seedlings to 12 inches when they are between 2 and 4 inches or have two sets of true leaves so you can transplant those you thin to a more desirable location. If it's any taller than that, the taproot is too developed to avoid damage.