Thelypodium eucosmum

Thelypodium eucosmum is a species of flowering plant in the mustard family known by the common names arrow-leaf thelypody[1] and world thelypody. It is endemic to Oregon in the United States, where it is known from Grant and Wheeler Counties.[2] There are also historical records of the plant from Baker County.[3]

Thelypodium eucosmum
Conservation status
Imperiled  (NatureServe)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Brassicales
Family:	Brassicaceae
Genus:	Thelypodium
Species:	T. eucosmum
Binomial name
Thelypodium eucosmum B.L.Rob.

This species is a biennial or short-lived perennial herb. It produces an erect, branching stem which can reach a meter in height. The basal leaves are lance-shaped or sometimes oval in shape and are borne on a short petiole. The leaves higher on the stem are smaller and have no petiole.[4] They may clasp the stem[3] or may be arrowhead-shaped, with projections extending around the stem. The inflorescence is a raceme of many flowers with purple petals. The fruit is a silique up to 6.5 centimeters long.[4]

This species occurs in the Blue Mountains of Oregon, and along tributaries of the John Day River.[5] Its habitat is dominated by sagebrush and juniper. It grows in moist areas such as river canyons and streambanks.[2][5] The plant's population size is greatly affected by the availability of water.[5] Other plants in the habitat may include Balsamorhiza spp., Bromus mollis, B. tectorum, Ericameria nauseosa, Gutierrezia sarothrae, Hordeum murinum, Lepidium spp., Purshia tridentata, Salix spp., Sarcobatus vermiculatus, and Urtica dioica.[3]

Grazing is a main threat to the species; some populations have been extirpated by livestock grazing.[5]