Asclepias tuberosa. Butterfly Bush Milkweed seeds, sometimes called Orange Milkweed, is a hearty perennial intensely attractive to butterflies and other beneficial garden insects. It is highly drought resistant, so useful for xeriscaping. Unlike other members of the Milkweed family, Butterfly Weed does not issue a milky sap when broken. Waxy green stems to 70cm (27") tall are topped by vivid orange flower clusters. Grown in small clusters, this plant attracts butterflies like no other, even in urban gardens. Flowers are followed by exotic looking fruits that release easy-to-harvest seeds. All milkweeds are useful, nectar rich food plants for butterflies, including the Monarch butterfly.
This is not the milkweed species that is used as a food plant by the Monarch caterpillar. That plant is A. incarnata, or Swamp Milkweed.
NOTE: All parts of the plant are harmful if swallowed. Asclepias leaves can be toxic to chickens, so plant out of range of foraging flocks.
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.