SafePlants

Green Milkweed (Asclepias viridis & Asclepias viridiflora) and Tall Green Milkweed (Asclepias hirtella)

This page provides information on Green Milkweed (primarily Asclepias viridis and Asclepias viridiflora), and Tall Green Milkweed (Asclepias hirtella), focusing on their characteristics and potential interactions with pets and children. Note that some sources refer to the same plant with different scientific names, reflecting taxonomic complexity.

Nomenclature and Taxonomy

• Scientific Names: Asclepias viridis, Asclepias viridiflora, Asclepias hirtella
• Common Names: Green Milkweed, Green Antelopehorn, Spider Milkweed, Tall Green Milkweed, Green Antelopehorn Milkweed, Short Green Milkweed
• Family: Dogbane Family (Asclepiadaceae, as noted for Green Comet Milkweed)
• Note: Older classifications may refer to Asclepias as formerly Acerates.
• Synonyms/Related Species: Mentions Matelea reticulata (Green Milkweed Vine, Pearl Milkweed) but does not make it clear if it's a synonym of Asclepias.

Distribution and Habitat

• Green Milkweed (Asclepias viridis) is most common in Texas, ranging from deep East Texas to the Edwards Plateau.
• It is also found in the Red Valley and low elevation limestone areas of some parks.
• It reaches the limit of its range in New England, where it can only be found in Connecticut (where it's endangered).
• Tall Green Milkweed (Asclepias hirtella) is found throughout the Tallgrass Prairie region, typically in prairies or remnants of prairies.
• It grows in full sun in sandy or rocky, calcareous soils of prairies and marshy areas.
• One variety is limited to serpentine and calcareous rocks in southeastern New York.
• Habitats include prairies, glades, along roadsides, moist areas, meadows, and beside fences and stream beds.

Morphology and Growth Habits

• Green Milkweed (Asclepias viridis) is a perennial from a vertical rootstock.
• It typically ranges from one to three feet in height (60-290 cm when described as a thick, hairy herb).
• The stems are mostly solitary or in pairs.
• Leaves are opposite, entire, and can be spreading to erect, opposite to subopposite.
• Flowers are light green, 5-parted, and about an inch long, forming round clusters about 2 inches across or green-yellow rounded flower clusters, often nodding. Some flowers have purplish accents.
• It has a taproot with a usually simple crown.
• Tall Green Milkweed (Asclepias hirtella) matures to 4 feet in height. It has abundant clusters of small pale green cylindrical flowers, tinged with violet hues. Stems are light green to light purplish green and more or less pubescent.
• Asclepias viridiflora grows to 1 meter (3ft 3in).
• The herbage is puberulent to tomentose.

Ecological Role

• Milkweed plants are essential for monarch butterflies.
• The loss of milkweed plants in the monarch’s spring and summer breeding areas is a concern, highlighting the importance of species like Asclepias asperula ssp. capricornu and Asclepias viridis.

Interactions with Other Organisms

• Phymateus viridipes, the Green Milkweed Locust or African Bush Grasshopper, feeds on milkweed.
• Praying mantises are found on milkweed.

Cultivation

• Green Milkweed is best propagated by seed, which is commercially available.
• It prefers dry-mesic to dry conditions in full sun.
• While it likes moist conditions initially, it doesn't need much water once established.
• It tolerates partial sun, mesic conditions, and rich loam if well-drained.

Resources

• Michigan Natural Features Inventory (P.O. Box 30444 - Lansing, MI 48909-7944, Phone: 517-373-1552)
• Native American Seed (for purchasing seeds)
• National Park Service (NPS)