Parcel
No. 5$4.50 Swamp Milkweed
Illustration of the No. 5 Swamp Milkweed seed packet: a kraft envelope with the Missouri Native Series stamp label and a SOW DEC–FEB postmark on the front, and the growing directions and label details on the back.
The packet

No. 5 in the Missouri Native Series

Swamp Milkweed

Asclepias incarnata

Missouri Native Series No. 5. Rose-pink, vanilla-scented monarch host plant for clay and damp spots. Blooms June–September.

$4.50packet

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Free shipping on orders of $25 or more, or on any order with a Winter-Sow Kit, The Complete Series or a Seed Club membership. Otherwise $3.95. Ships in 2–4 business days. We ship to the 48 contiguous states and D.C., except Colorado, Kentucky, Minnesota, Nebraska, Ohio, Pennsylvania and Wisconsin for now. Shipping details

  • Missouri native seed, packed for 2027
  • Postmarked to sow December to February, outdoors (winter sowing)
  • Grow Guarantee: if it doesn't come up after you follow the guide, we'll send a replacement

Don’t let the name put you off. Swamp milkweed grows wild in Missouri’s moist river bottoms, but it’s just as happy in an ordinary garden bed, and it handles the heavy, poorly drained clay that stumps other flowers.

In summer it carries clusters of rose-pink flowers with a faint vanilla scent that butterflies can’t resist, and monarchs lay their eggs on its leaves. If you have a low spot that stays soggy in spring, this is your milkweed.

It needs a winter chill to sprout. Each packet is hand-filled in St. Charles County, Missouri.

Good to know

  • Toxic if eaten. Keep pets and livestock from grazing it.
  • Milky sap can irritate skin and eyes; wear gloves if you’re sensitive.
  • Aphids are common on milkweed. Leave them for ladybugs, or rinse them off with a strong spray of water or soapy water.

How to grow

  1. Pick the spot. Full sun to light shade, in average to wet soil. A rain garden, a low corner or the edge of a pond is ideal, but a regular bed works too.
  2. Sow in late fall or winter. Between November and February, sow on bare, weed-free soil or in a winter-sowing jug, about 1/8 to 1/4 inch deep. See our winter sowing guide.
  3. Or use the fridge. Chill the seed in damp sand for 30 days, then sow after the last frost. Here’s the fridge method.
  4. Keep it moist. Swamp milkweed likes steady moisture, especially its first year.
  5. Let the caterpillars eat. Chewed leaves mean monarchs found it. Aphids are common on milkweed; leave them for ladybugs or rinse them off with water.

Good neighbors

Species from the series that grow well alongside Swamp Milkweed:

Questions

Do I need a swamp to grow it?

No. It grows naturally in wet places, but Grow Native! notes it also grows well in the garden and in poorly drained clay. Average garden moisture is fine.

Is swamp milkweed good for monarchs?

Yes. Monarch caterpillars feed on its leaves, and adult butterflies visit the flowers for nectar.

Is it safe around pets?

No milkweed should be eaten. The ASPCA lists milkweeds as toxic to dogs, cats and horses, and NC State Extension notes the milky sap can irritate skin and eyes. Plant it where pets and livestock won’t graze it.

What do the flowers smell like?

Grow Native! describes a faint vanilla fragrance. Butterflies seem to agree that it’s worth a visit.

Sources for these facts