Purple Milkweed for Monarch Caterpillars and Beneficial Pollinators
Asclepias purpurascens: Purple milkweed
- Perennial: USDA hardiness zones 3a-9b (lows -40 °C or -40 °F)
- Native to most of the eastern US and Ontario Canada
- Full sun to part shade
- Height: 2 to 3 feet
- Spacing: 1 to 3 ft
- Flowers: rich rose to a light purplish color
- Blooms late spring to early summer
- Milkweed pods are smooth and thin compared to common milkweed
- Sow seeds directly outside in fall- November is a good option for most regions
- Start seeds indoors 2 months before final frost- seeds must be cold stratified
- Sow seeds directly after final frost
- Winter sowing is a good option to control plant placement
- Not an aggressive spreader like its common counterpart
- Fragrant flowers are popular with pollinators
- Pretty purple flowers (in multiple shades) are some of milkweed’s finest
- Sweet fragrant blossoms that fill air in late spiring and early summer
- Easier to transplant successfully with no underground rhizome
- Seeding can be an issue with mature plants
- More difficult to establish due to lack of an underground rhizome
- Difficult to find plants/seeds locally or online…get them when you have the opportunity!
- Unknown– because few gardeners report growing this successfully, there is still more to learn about best growing practices
- Pest Favorite? After planting 7 plants last fall, they were all mowed to the ground by small critters (rabbits?) within two days. Hopefully, this will not be a recurring theme…
Purpurascens Growing Tips:
- Easiest to sow outside directly in fall (spring also works with cold stratification)
- This species is supposedly adaptable to a wide range of growing conditions, but this seems unlikely considering this milkweed is a rare find in the wild, let alone in nurseries.
- Since Asclepias purpurascens does not have a long tap root to store excess nutrients, I question reports of drought tolerance.
- Ours is planted in well-drained soil but it’s not overly dry. We mixed in composted manure before planting our purple milkweed last fall.
- Our plants will receive morning/early afternoon sun, but get a shady reprieve from the sizzling afternoon sun.
- Segregate purple from aggressive spreaders like common milkweed so your plants aren’t overcome by ravenous rhizomes.
- Protect your plants! Since these seem more difficult to establish consider putting up a fence to keep away small critters. We left ours up over winter and will leave it until the plants establish themselves next season.
- Cut I- If you don’t want additional seedlings next spring, simply cut off the seed pods before they pop open or bind them shut with twist ties or rubber bands if you want to collect purple milkweed seeds.
- Check back for more updates (with photos) as we try to unlock the secrets of successfully growing Asclepias purpurascens.
Purple milkweed also attracts azures, bumble bees, eastern black swallowtails, eastern tiger swallowtails, great spangled fritillaries, hairstreaks, painted lady butterflies, skippers, sulphurs, and more… (If you know of others, please comment below.)
Click here to Discover More Milkweed Options for your Butterfly Garden