Cooley's meadowrue (Thalictrum cooleyi Ahles) is a perennial herb which grows from a rhizome. The stems are usually 3.3 feet (ft) (1 meter; m) in height, but sometimes grow as high as 6.6 ft (2 m) on recently burned sites. Under ideal conditions, in full sun, these stems are erect; however, when shaded they are lax and may trail along the ground or lean on other plants. The compound green leaves are divided into three parts and the leaflets are lance-shaped and less than 2 centimeters long. The plant has both basal and stem leaves. All parts of the plant are glabrous, having virtually no hairs or glands. Each plant is unisexual, and the male to female ratio is 3 to 1. The flowers have no petals. The sepals on the male plants are pale yellow to white. There are numerous stamens, and the filaments are pale lavender. Female plants have green sepals, and their short-stalked, ribbed carpels develop into narrowly ellipsoidal achenes.

Habitat: Cooley's meadowrue occurs on circumneutral soils in wet pine savannahs and savannah like areas. It may also grow along fire plow lines, in roadside ditches, woodland clearings, and powerline rights-of-way, and needs some type of disturbance such as fire or mowing to maintain its open habitat. Plants often found growing with Cooley’s meadowrue include tulip poplar growing with bald cypress and/or Atlantic white cedar.

Threats: Cooley’s meadowrue is threatened by loss of habitat, ecological succession, clearing for agriculture, forestry, herbicide application to power line corridors, development and road maintenance and construction projects.

References:

Buchanan, M.F. and J.T. Finnegan. 2010. Natural Heritage Program List of the Rare Plant Species of North Carolina. NC Natural Heritage Program, Raleigh, NC.

Cooley's meadowrue flowers in mid June to early July. The fruits are spindle-shaped carpels which develop into 6 millimeter long achenes, maturing in August or September, and remaining on the plant into October. If the plants grow in partial shade instead of full sun, flowering may be delayed by as much as two weeks.