Swamp Milkweed

Scientific Name: Asclepias incarnata

Light: Sun to part shade

Zone:  3 to 6 or 9 depending on source

Height:  4 to 6 feet

Width:  2 to 3 feet

Flowers:  May to June; Pink to reddish

Fruit/Seed:  August to November; pod

Fall Color:

Butterflies:   Swamp milkweed is a favored food of monarch butterfly larva. Various other butterflies consume nectar from the flowers.

Birds:

Hummingbird:  Hummingbirds consume nectar from the flowers.

Deer Resistant:  Seldom severely damaged

Insects/Pollinators:  attracts

Native:  Carroll and throughout Maryland

Idea Garden:

Propagation:  Collect seeds in the fall, when the brown pods are dry and have begun to split. Crack the pods open completely allowing the seeds to dry for one to two weeks in paper bags. Look for signs of damage. Once they are dry, place the seeds into plastic bags filled with moist perlite or vermiculite and store them in a cold place, approximately 35 to 38 degrees Fahrenheit, for at least 4 to 12 weeks (stratification). For purchased seeds, cold stratify for at least 4 weeks.  Good germination results have been reported without stratification by soaking the seed. Soak the seed in hot water (190 degrees Fahrenheit) for 12 hours. Repeat this process two additional times for expected seed germination of 50%. Seed can be placed in cold storage for up to three years. To grow plants, press the seed gently into the soil, three seed per cell, and cover with a very thin layer of soil or vermiculite. Temperatures should remain between 65 and 75 degrees Fahrenheit. Swamp milkweed seed requires light for germination. Germination is poor at temperatures higher than 85 degrees Fahrenheit. Seedlings should not be transplanted until they have at least one set of true leaves. Allow 4 to 8 weeks inside growing time for seedlings before moving to a cold frame or transplanting outside. Plants can be moved outside once the danger of frost has passed.

Swamp milkweed spreads through rhizomes; established plants can be divided in late spring.

Description

Swamp milkweed is a tall plant with beautiful, fragrant white to  pink and light purple flowers that does well in moist soils.  Swamp milkweed tolerates heavy clay soils and is very deer-resistant.  Common milkweed is preferred by monarch caterpillars but swamp milkweed is a more refined alternative for gardens.  Since it does not have a tap root, swamp milkweed is the only native milkweed that does well in containers.

Cultivars / Varieties

Cinderella – 40”; Long lasting rose-red flowers w’ pinkish centers.

Ice Ballet – 48”; Pure white, long lasting flowers.

Soulmate – 24 to 36″; rose-pink flowers

Milkmaid – 36-48″; white flowers

Sources

Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed

Swamp Milkweed – USDA Plant Fact Sheet

Swamp Milkweed – Missouri Botanical Garden

Landscape Plants Rated by Deer Resistance – Rutgers

Specialty Cut Flowers by Armitage & Laushman

The Flower Farmer by Lynn Byczynski

Recommended for Wildlife by

Creating a Wild Backyard – Hummingbirds, Butterflies & Bees – Maryland DNR

Some Favorite Nectar Plants – Washington Area Butterfly Club

Butterfly Gardening in the DC Area – Washington Butterfly Club

Bees, Bugs & Blooms – A pollinator trial – Penn State

Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed

 For the Birds, Butterflies & Hummingbirds: Creating Inviting Habitats – Virginia Extension

 Top Nectar Plants, Piedmont (Central Maryland) by North American Butterfly Association

Bring Home The Butterflies Vol. I: How to Attract More Monarchs to your Butterfly Garden…and Keep Them There! by Tony Gomez

Butterflies of Maryland:  A biological summary and checklist by Maryland DNR

Photo Credits

Jennifer Anderson, hosted by the USDA-NRCS PLANTS Database

Additional information

Zones

Zone 5, Zone 6, Zone 7, Zone 8

Light

Part Sun, Sun

Soil

Clay, Loam, Moist, Wet

Flower Color

Pink, Red

Flower Season

Spring, Summer

Fruit Season

Fall, Summer

Wildlife Value

Beneficial Insects, Butterfly Host, Deer Resistant, Hummingbird, Nectar

Notable Features

Containers, Cut Flowers, Fragrant, Rain Garden

Local Availability

Available, Widely Available

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