Species Native to Missouri
Common Name: prairie milkweed
Type: Herbaceous perennial
Family: Apocynaceae
Native Range: Eastern and central United States
Zone: 4 to 8
Height: 2.00 to 3.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: June to August
Bloom Description: Purple-tinged greenish-white
Sun: Full sun to part shade
Water: Dry to medium
Maintenance: Low
Suggested Use: Naturalize
Flower: Showy
Attracts: Butterflies
Tolerate: Deer, Drought, Clay Soil, Dry Soil
Culture
Easily grown in average, dry to moist, sandy or gravely, 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 but are not considered overly aggressive. Performs poorly in wet soils. Difficult to transplant because of deep roots.
Noteworthy Characteristics
Asclepias hirtella, commonly known as tall green milkweed or prairie milkweed, is an upright herbaceous perennial that typically grows to 3’ tall on one or more unbranched stems. This is an uncommon species that is native to upland prairies, rocky glades, sandy wetland margins, roadsides, pastures and abandoned fields from Ontario and Minnesota south to Kansas, Louisiana and Georgia. The alternately arranged leaves are narrow-linear to linear-lanceolate shape in shape and will reach 2-6" long. Like all milkweeds, the stems and leaves exude a milky sap when cut. Rounded, almost spherical, 2-inch diameter umbels, each containing 30-100 tiny, purple-tinged-greenish-white flowers (to 1/8” across), develop in the middle to upper leaf axils in summer. Each individual flower has 5 sepals (lobed calyx), 5 petals (lobed corolla), and 5 upright cup-like hoods (horns absent). The reflexed 5-lobed corolla curves backward and downward toward the center of the umbel, displaying the 5 hoods which are in general a key diagnostic feature of milkweed family plants. Flowers are followed by smooth narrow seedpods (4-5” long) which split open when ripe to release 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 means rather hairy.
Common names are in reference to plant size and typical habitat.
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. Cottage gardens. Rock gardens.
Seed pods are valued in dried flower arrangements.