Species Native to Missouri
Common Name: whorled milkweed
Type: Herbaceous perennial
Family: Apocynaceae
Native Range: United States
Zone: 4 to 9
Height: 1.00 to 2.50 feet
Spread: 1.00 to 2.00 feet
Bloom Time: June to September
Bloom Description: White
Sun: Full sun to part shade
Water: Dry to medium
Maintenance: Low
Suggested Use: Naturalize
Flower: Showy
Attracts: Hummingbirds, Butterflies
Tolerate: Deer, Drought, Dry Soil
Culture
Easily grown in average, dry to medium moisture, well-drained soils in full sun. Tolerates part shade. Best in sunny locations with sandy loams. Drought tolerant. Easily grown from seed, and will self-seed in the landscape if seed pods are not removed prior to splitting open. Likes hot dry soils, but tolerates moist garden soils. Plants will spread by rhizomes and can be considered aggressive particularly in small garden areas.
Noteworthy Characteristics
Asclepias verticillata, commonly known as whorled milkweed, is an upright, rhizomatous perennial native to ridges, bluffs, glades, prairies, and other open, upland habitats as well as woodlands, wet meadows, streambanks, and forest edges in much of the eastern United States. Mature plants typically reach 2.5’ tall with simple, usually unbranched stems clad with long, narrow, sessile, needle-like, linear leaves (each 2-3” long) with revolute margins arranged in whorls of 3 to 6 at each node along the length of the stems. Stems and leaves ooze a milky sap when cut or broken. Flowers bloom in small clusters (umbellate cymes of 3-20 flowers) in the upper leaf axils and stem ends between June and September. Flowers are fragrant. Each tiny flower (to 1/4” long) has a 5 lobed calyx, 5 greenish-white corolla lobes and 5 white hoods with incurved horns protruding from each hood. Flowers give way to smooth, narrow seed pods (to 3” long) which split open when ripe releasing numerous silky-tailed seeds for dispersal by the wind.
The charismatic and imperiled monarch butterfly requires milkweed plants in order to survive. Monarchs migrate into the eastern U.S. from Mexico in spring to lay their eggs on milkweed species plants. Caterpillars hatch from the eggs and consume the milkweed plant foliage as food for growth and development. Mature caterpillars will search for a nearby, sheltered location to enter the pupal stage and form a chrysalis. Inside, they will complete metamorphosis and emerge as an adult butterfly in around 2 weeks. Flower nectar is consumed by adult butterflies as a valuable food source. The 4th or 5th generation of monarch butterflies that emerges in August-September will migrate into Mexico to overwinter as adults. Significant declines in monarch butterfly populations in North America over the course of the 21st century are believed by many experts to be caused by a reduction in milkweed due to widespread use of herbicide-tolerant row crops, climate change, and loss of overwinter sites due to habitat destruction.
To support monarch butterflies, plant species of milkweed that are native to your area.
Genus name honors the Greek god Asklepios the god of medicine.
Specific epithet comes from the Latin word verticillatus meaning whorled in reference to the leaves appearing in whorls.
Common name suggests this plant is noted for its whorled leaves and milky sap. Additional common names for this plant include horsetail milkweed.
Problems
No serious insect or disease problems. Aphids can be problematic but attempting to control them can result in inadvertent harm to monarch caterpillars and other beneficial insects.
Uses
Butterfly gardens, meadows, prairies, or naturalized/native plant areas. Borders. Seedpods can be used in dried flower arrangments.