Asclepias speciosa. Native to western and central North America (including BC's Okanagan region), Showy Milkweed is the plant at the center of Monarch butterfly conservation efforts. This is the particular species of milkweed that the Monarch caterpillars feed on after hatching, so it is highly prized by egg-laying adults. The flowers are notoriously generous with nectar, so they attract a host of other butterfly species, as well as bees, hummingbirds, and many other pollinators. The plants grow to around 90cm (36") tall, with greyish green foliage topped by spherical clusters of pink flowers. Once the seed pods form, they can be cut and dried to good effect. Plant Showy Milkweed seeds anywhere to help with pollinator conservation.
Note: This species spreads by self-seeding as well as spreading its rhizomatous roots. In favorable settings, it can spread aggressively. For this reason, we recommend it for larger containers or for areas where it can be controlled through regular pruning. To avoid self-sowing, simply cut the seed pods off before they mature.
Showy Milkweed also happens to be pretty much deer-proof.
When transplanted seedlings are 10-15cm (4-6″) tall, pinch back the growing tip to encourage multiple flowering points. Asclepias tuberosa prefers dry, sandy conditions or any average garden soil in full sun. Plants grown from seed bloom in the first year if given an early start. They can be pulled up in fall and treated like annuals to prevent spreading. Asclepias does not divide well, but it’s an outstanding choice for xeriscaping. Asclepias speciosa and some of the others do better in swampy soil, but they are not fussy plants. Continue reading below for some more specific advice on how to grow Asclepias from seed.
Season & Zone
Exposure: Full sun
Zone: Hardy to Zone 3
Sow indoors 6-8 weeks before the last frost date and transplant or direct sow towards late spring. Optimal soil temperature for germination: 10-25°C (50-75°F). Seeds should sprout in 7-35 days. Asclepias may benefit from stratification: Seeded trays are wrapped in plastic and refrigerated for two to three weeks before being placed over bottom heat. This may result in more even and speedier germination.
We have had success direct sowing A. tuberosa in March, with blooms the first year. In our experience, A. speciosa returns with vigour in the second year and begins blooming by June here on the west coast.
Barely cover the small seeds using sterilized seed starting mix. Space transplants 30-60cm (12-24″) apart.
For many years several Asclepias species were listed as invasive weeds because of their sometimes aggressive spreading by underground rhizomes and their giant, dandelion-like seeds. The seeds emerge from very conspicuous pods which are easily removed before they dry and crack. As the population of wild Asclepias diminished, so did the populations of many butterflies that depend on them as food and nursery plants (including the endangered Monarch). Now that they have been de-listed, we encourage home gardeners to grow them with the advance knowledge that they can spread. Try growing them in a large container like a half barrel, and be conscious of the seed pods as they develop. In short, please be responsible with Asclepias species.
Note: All parts of the plant are harmful if eaten. Flowers are not edible.
Download our Asclepias tuberosa Factsheet.