''Thelypodium eucosmum'' is a species of flowering plant in the

mustard family Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The le ...

known by the common names arrow-leaf thelypody and world thelypody. It is endemic to Oregon in the United States, where it is known from Grant and Wheeler Counties.''Thelypodium eucosmum''.
Center for Plant Conservation. There are also historical records of the plant from Baker County.''Thelypodium eucosmum''.
Oregon Department of Agriculture. 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.''Thelypodium eucosmum''.
Flora of North America. They may clasp the stem or may be arrowhead-shaped, with projections extending around the stem. The inflorescence is a

raceme A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...

of many flowers with purple petals. The fruit is a silique up to 6.5 centimeters long. This species occurs in the Blue Mountains of Oregon, and along tributaries of the John Day River.''Thelypodium eucosmum''.
NatureServe. Its habitat is dominated by sagebrush and

juniper Junipers are coniferous trees and shrubs in the genus ''Juniperus'' () of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere, from the Arcti ...

. It grows in moist areas such as river canyons and streambanks. The plant's population size is greatly affected by the availability of water. Other plants in the habitat may include ''

Balsamorhiza ''Balsamorhiza'' is a genus of plants in the family Asteraceae known commonly as balsamroots. These are perennials with fleshy taproots and caudices bearing erect stems and large, basal leaves. Atop the tall stems are showy yellow sunflower-like ...

'' spp., '' Bromus mollis'', '' B. tectorum'', ''

Ericameria nauseosa ''Ericameria nauseosa'' (formerly ''Chrysothamnus nauseosus''), commonly known as Chamisa, rubber rabbitbrush, and gray rabbitbrush, is a shrub in the sunflower family (Aster) found in the arid regions of western North America. Two subspeci ...

'', '' Gutierrezia sarothrae'', '' Hordeum murinum'', ''

Lepidium ''Lepidium'' is a genus of plants in the mustard/cabbage family, Brassicaceae. The genus is widely distributed in the Americas, Africa, Asia, Europe, and Australia.Purshia tridentata ''Purshia tridentata'', with the common name bitterbrush, is a shrub in the genus '' Purshia'' of the family Rosaceae. It is native to mountainous areas of western North America. Common names include antelope bitterbrush, antelope bush, buc ...

'', '' Salix'' spp., '' Sarcobatus vermiculatus'', and '' Urtica dioica''. Grazing is a main threat to the species; some populations have been extirpated by livestock grazing.

References

{{Taxonbar, from=Q7781140 eucosmum Flora of Oregon Endemic flora of the United States Grant County, Oregon Wheeler County, Oregon Endangered flora of the United States Endemic flora of Oregon