Asclepias incarnata. Swamp Milkweed begins to grow from a thick, fleshy root later in spring than many other plants. Narrow, strap-like leaves emerge, forming a clump of foliage. Then, from mid-spring to late summer, umbels of fragrant, pink to mauve flowers appear that are so generous with nectar that they attract butterflies and important pollinators of all kinds. The roots of this plant have evolved to thrive in low oxygen environments, including the wet soil found around lakes and streams. The plants can reach 2m (6') in height, and will grow in full sun to partial shade. It is hardy to Zone 3.
Perennial.
West Coast Seeds Swamp Milkweed Asclepias Seeds, Per Package
Starting
Barely cover the small seeds using sterilized seed starting mix. Space transplants 30-60cm (12-24″) apart.
Timing
Sow indoors 6-8 weeks before the last frost date and transplant towards late spring. Milkweed requires cold stratification to break dormancy. Sow the seeds in damp soil in 18 cell plug inserts and place in a refrigerator for two weeks or place outside in early spring. Transplant when the seedlings are 2 inches (5cm) tall. Optimal soil temperature for germination: 10-25°C (50-75°F). Seeds should sprout in 7-35 days.
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.
