Swamp milkweed is an herbaceous perennial in the Apocynaceae (dogbane) family. Apocynum is the Greek term for “dog-away.” It is native to the central and eastern United States and tends to grow in wet sites along streams, ponds, or bogs. Plant swamp milkweed in full sun to partial shade in soils with neutral to acidic pH. It is native to wet sites but adapts to drier sites in moist clay or loam soils. The attractive pink to rose-purple flowers mature in mid-spring and last into early fall. The seed pods split open to release seeds that float on the wind. Milkweed is an important food source for Monarch butterfly caterpillars ( Danaus plexippus ) , and the flowers are visited by many pollinators. It is resistant to browsing by deer. Use as an accent or border in a meadow, native, or pollinator garden. It will be at home in a naturalized area or along a pond or stream where it can grow up to 5 feet tall and spread 2 to 3 feet wide. This plant was selected as the 2005 NC Wildflower of the Year , a program managed by the North Carolina Botanical Garden with some financial support from the Garden Club of North Carolina. Insects, Diseases, and Other Plant Problems: No significant disease problems. Most common milkweed pests (aphids, milkweed beetles, Monarch larvae, and milkweed tussock moth larvae) are not problematic, but both large and small milkweed bugs can be very damaging to seed pods.
Source: NC State Extension Gardener Plant Toolbox ↗Reconciled to full toolbox: matched by slug to slug 'asclepias-incarnata'. Identity (id/common/scientific name) preserved from the original 87-plant Hunnicutt set; attribute data refreshed from the 72-attribute toolbox scrape.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Clay; High Organic Matter; Loam (Silt)
Soil pH
Acid (<6.0); Neutral (6.0-8.0)
Soil drainage
Good Drainage | Moist | Occasionally Wet
Available space
3 feet-6 feet
NC region
Coastal; Mountains; Piedmont
Mature size
Height: 3 ft. 0 in. - 5 ft. 0 in. | Width: 2 ft. 0 in. - 3 ft. 0 in.
Growth rate
Medium
Maintenance
Low
Canopy layer
4 - Herbaceous (3-15 ft)
Form & Appearance
Habit / form
Clumping; Erect
Foliage
Deciduous
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Opposite
Leaf shape
Lanceolate; Oblong
Leaf margin
Entire
Leaf feel
Smooth
Leaf size
3-6 inches long, < 1 inch wide
Hairs present
No
Leaf detail
Lanceolate to oblong-lanceolate green leaves are 3-6 inches long .5 to 1.5 inches wide with pointed apex and entire margins. They are either sessile or clasping.
Flower color
Pink; White
Flower value
Fragrant; Showy
Flower form
Umbel
Flower shape
Crown
Flower size
< 1 inch
Flower detail
Individual flowers are ¼" across, consisting of 5 white upright crowns and 5 surrounding pink to mauve petals that droop downward. Blooms in clusters called umbrels on terminal stems. Flower blooms from July to September.
Bloom time
Fall; Summer
Fruit color
Brown/Copper; Cream/Tan; White
Fruit type
Follicle
Fruit value
Showy
Fruit size
> 3 inches long, 1-3 inches wide
Fruit detail
3-4-inch long follicle seed pods split on one side to release seeds with tufts of hair that float on the wind. They are green and mature to brown.
Stem color
Green
Stem detail
Stems exude a toxic milky sap when cut.
Wildlife & Ecology
Native status
Native
Origin
Central & E. Canada to W. Central & E. U.S.A.
Distribution
Northeastern and southeastern United States
Wildlife value
This plant provides nectar for pollinators including Monarch (Danaus plexippus) butterflies. It is the larval host plant for Monarch (Danaus plexippus) larvae. Its flowers are attractive to pollinators. Deer tolerant.
Attracts
Butterflies; Pollinators; Predatory Insects
Host plant for
Monarch (Danaus plexippus) larvae
Play value
Wildlife Food Source
Food & Medicine
Harvest time
Fall
Fruit type
Follicle
Landscape Use
Landscape location
Coastal; Meadow; Near Septic; Pond; Pool/Hardscape; Riparian; Slope/Bank
#pollinator plant #native perennial #NC native #butterfly friendly #Monarch butterfly #wet soils tolerant #flowers late spring #flowers early summer #border planting #flowers mid-summer #low maintenance #flowers early fall #flowers late summer #purple flowers #NC Wildflower of the Year #native wildflower #deer resistant #boggy sites #nectar plant #collier preserve tn #rabbit resistant #accent #rain garden #HS303 #cpp #fiber plant #beneficial insects
Problems & Resistance
Insect problems
Milkweed Bug; Aphids on Ornamental Landscape Plants
Problems
Contact Dermatitis; Poisonous to Humans; Problem for Cats; Problem for Dogs; Problem for Horses
Resistant to
Deer; Rabbits; Wet Soil
Particularly resistant to
Deer and rabbit resistant
Fire risk
medium flammability
Poison severity
Low
Poison parts
Flowers; Fruits; Leaves; Roots; Seeds; Stems
Poison symptoms
Can cause stomach upset, nausea, vomiting, abdominal pain, diarrhea, weakness, lethargy, and confusion if eaten in quantity. Milky sap can cause contact dermatitis and eye irritation