Growing Asclepias From Seed

Many of our customers want to grow butterfly weed (Asclepias tuberosa) or common milkweed (Ascelpias syriaca) from seed. These native plants are pretty, support pollinators, and are a host plant for monarch larvae, so it’s no wonder that people want to include them in gardens. The common milkweed is also fragrant, and its perfume is delightful when the plant is in bloom. The seeds for both of these plants may be in your garden right now, but don’t just collect them and stick them away for the winter. These seeds will not germinate if you keep them indoors until spring.

Milkweed and butterfly seeds need a chilling period to sprout.

If you’ve tried growing these seeds indoors in the past, you’ve undoubtedly seen that they don’t sprout. These are seeds that need a chilling period, known as stratification. This is the process that exposes seeds to cold and/or warm temperatures, sometimes with moisture, to break dormancy and initiate the germination process. This mimics natural winter conditions that some seeds require to sprout.

While you might see online recommendations to put the seeds in the refrigerator, it’s far more effective to give the seeds what nature does: damp soil and being outdoors, all winter long. You can smear the seeds over the soil where you want them to grow, but they may wash or blow away, or be eaten by wildlife. Far better to fill some plastic pots with damp seed-starting mix, press several seeds on the top of that mix (don’t cover the seeds) and water well. Then cut some pieces of floating row cover and tape them over the pots.

The floating row cover allows light and water to enter, but keeps out critters and weed seeds. Place these in a sheltered spot that’s open to the weather so that the pots will be watered when it rains. In early May, remove the row cover and water the pots every three days if it doesn’t rain.