Culture
Best grown in evenly moist, rich, well-draining soils in part sun to full shade. Hardy in Zones 4-8.
Noteworthy Characteristics
Asclepias exaltata, commonly called poke milkweed, is a herbaceous perennial native to forest openings and edges in the northeastern United States, Great Lakes region, parts of the northern Midwest, and south through the Appalachian Mountains to far northern Georgia and Alabama. Mature plants will reach 4-6' tall and spread to fill a 2-4' area. The oppositely arranged, broadly lanceolate to ovate foliage will reach around 3-8" long and 1-3" wide. The upright stems are topped with loose, terminal umbels of small, green and white flowers in from early to mid-summer. Like all milkweeds, the stems and leaves exude a milky sap when cut. The flowers are attractive to butterflies and other insect pollinators.
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.
The specific epithet exaltata means "very tall" and refers to the potential height of this species.
The common name poke milkweed refers to the similar appearance of this plant to Phytolacca americana, American pokeweed. A now synonymous name for this species was Asclepias phytolaccoides which means "poke-like 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
Partly shaded mixed borders, naturalistic plantings, butterfly gardens.