Asclepias perennis
aquatic milkweed
Southeastern and south-central United States
Overview
Asclepias perennis is a herbaceous perennial milkweed 12-36 inches (30-90 cm) tall, with slender, often branched stems rising from a fibrous root system. The narrow lance-shaped leaves are 2-6 inches (5-15 cm) long, paired along the stems, and the plant exudes a milky white sap when cut. From late spring through summer it carries flat-topped clusters of small white flowers, sometimes flushed pink, each with the reflexed petals and raised central crown typical of milkweeds. The flowers are followed by slender seed pods 2-4 inches (5-10 cm) long that release flattened seeds; unlike most milkweeds, the seeds have little or no silky floss and drift on water rather than wind. The plant grows in swamps, floodplain forests, ditches, and pond margins across the southeastern United States, tolerating standing water and seasonal flooding. It supports monarch and queen butterflies as a larval food plant and draws many nectar insects. All parts contain toxic cardiac glycosides. It needs consistently wet soil and declines in dry ground.
Native Range
Asclepias perennis is native to the southeastern and south-central United States, from South Carolina and Florida west to Texas and north along the Mississippi valley to Missouri and Indiana. It grows in swamps, floodplain woods, wet ditches, and the margins of ponds and slow streams.Suggested Uses
Used in rain gardens, bog gardens, pond edges, and wet meadow or pollinator plantings. It serves as a larval host for monarch and queen butterflies and a nectar source for bees and wasps. Suited to wet sites where most other milkweeds fail.How to Identify
Appearance
Size & Dimensions
Height1' - 3'
Width/Spread1' - 2'
Reaches mature size in approximately 2 years
Bloom Information
Flat-topped clusters of small white, sometimes pink-flushed flowers open from late spring through summer, often over a long season in warm climates. Bees, wasps, and butterflies pollinate them. Slender pods follow and split to release water-dispersed seeds.
Detailed Descriptions
Flower Description
white, sometimes pink-tingedFoliage Description
greenGrowing Conditions
Sun Requirements
Requires 4-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Asclepias perennis grows in full sun to part shade on wet to consistently moist soils and tolerates standing water and seasonal flooding. It establishes easily from seed, which needs little or no cold treatment, and from division in spring. Unlike dry-land milkweeds, it depends on steady moisture and will not persist in dry borders. It self-sows where soil stays wet and can form small colonies. All parts contain toxic cardiac glycosides. Hardy in USDA zones 6-9, it dies back in winter and returns from the roots in spring.Pruning
Spent flower clusters can be removed to extend bloom or left to form seed pods. Stems are cut back to the ground in late autumn or late winter after they die down. No other pruning is required.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
fallwinter
Container Growing
✓ Suitable for container growing
Minimum container size: 2 gallons