hemp dogbane

Apocynum cannabinum grows up to 1 m (3 ft 3 in) tall. The stems are reddish and contain a milky latex. The leaves are opposite, simple, broad, and lanceolate, 7–15 cm (2+3⁄4–6 in) long and 3–5 cm (1+1⁄4–2 in) broad, entire, and smooth on top with white hairs on the underside. It flowers from July to August, has large sepals, and a five-lobed white corolla. The flowers are hermaphrodite, with both male and female organs. The seeds have white, silky hairs to aid in wind dispersal, but the lightweight seed is also able to disperse via water due to its light weight. The root system consists of short rhizomes and horizontal roots.

Apocynum cannabinum grows in open wooded areas, ditches, and hillsides. It is found in gravelly or sandy soil, mainly near streams in shady or moist places. It is also found in human-disturbed habitats. It is native to much of North America—in the southern half of Canada and throughout the United States.

The plant serves as a larval host for the snowberry clearwing (Hemaris diffinis), which is a pollinator that resembles a small hummingbird. It is also a host plant for the dogbane tiger moth (Cycnia tenera) and the zebra caterpillar (Melanchra picta). The larvae of Marmara apocynella feed on the stems, making a "long whitish serpentine mine". Apocynum cannabinum is primarily pollinated by insects that are attracted to the fragrance and nectar of the flower.

The seeds have an edible use as a meal (raw or cooked) when ground into a powder.

It is used in herbal medicine to treat fever and to slow the pulse. Apocynum cannabinum has been employed by various Native American tribes to treat a wide variety of complaints including rheumatism, coughs, pox, whooping cough, asthma, internal parasites, diarrhea, and to increase lactation. The root has been used as a tonic, cardiotonic, diaphoretic, diuretic, an emetic (to induce vomiting), and an expectorant. It is harvested in the autumn and dried for later use. The fresh root is medicinally the most active part. A weak tea made from the dried root has been used for cardiac diseases and as a vermifuge (an agent that expels parasitic worms). The milky sap is a folk remedy for genital warts. However, both illness and deaths have resulted from use as a medicine.

Apocynum means "poisonous to dogs". The specific epithet cannabinum, and the common names hemp dogbane and Indian hemp refer to its similarity to Cannabis as a source of fiber. It likely got its name from its resemblance to a European species of the same name. It is called qéemu [qǽːmu] in Nez Perce and [taxʷɨ́s] in Sahaptin. The Maidu Concow people call the plant pö (Konkow language).