Horsetail milkweed, also known as Asclepias subverticillata, is a plant species that belongs to the milkweed family. This species is native to North America and is commonly found in moist, open areas such as prairies, streambanks, and wetlands. Horsetail milkweed is also known by several other names, including eastern horsetail milkweed, clasping-leaf milkweed, and sand milkweed. The plant is valued for its showy clusters of pink or purplish flowers, which bloom in the summer and attract pollinators such as bees and butterflies. Apart from its ornamental value, horsetail milkweed is also considered an important host plant for monarch butterfly larvae.