Slender Thelypody - Thelypodium sagittatum
State Rank Reason (see State Rank above)
Known from numerous occurrences in extreme southwestern Montana.
Slender Thelypody is an herbaceous biennial or short-lived perennial with solitary, simple or branched stems that are 3-8 dm high and arising from a taproot. The lower leaves are 6-20 cm long and have petioles and broadly lance-shaped, entire-margined blades. The upper leaves are smaller, narrowly arrow-shaped, and they lack petioles. Foliage is glabrous or nearly so and has a thin, waxy coating. Flowers are densely clustered on ascending stalks in cylindric inflorescences that expand greatly when in fruit. Each flower has 4 separate sepals that are 3-7 mm long, 4 separate, lavendar petals that are 7-14 mm long and 1-3 mm wide, and 4 long and 2 short stamens. The ascending, straight, cylindric siliques are 18-53 mm long and less than 1 mm wide.
Flowering and fruiting from the end of May to mid-July.
Only the typic subspecies is in Montana. This taxa is similar to T. paniculatum, but the latter has fruits that are greater than 1.3 mm wide and petals that are greater than 2.5 mm wide. T. sagittatum might also be confused with species of Arabis, but those plants have flattened rather than cylindrical siliques.
Southeastern WA to CA, east to MT and WY.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Moist, alkaline meadows, often with greasewood or shrubby cinquefoil, in the valley to montane zones.
Ecological Systems Associated with this Species
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana's populations of Slender Thelypody are currently assigned as unknown. Potential threats due to livestock trampling and grazing are negligible according to reported data (MTNHP Threat Assessment 2021).
- Additional ReferencesLegend: View Online Publication
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- Al-Shehbaz, I. A. 1973. The biosystematics of the genus Thelypodium (Cruciferae). Contributions from the Gray Herbarium No. 204:3-148.
- Haglund, B.M. 1972. Ecological effects of weather modification, Bangtail Ridge, Bridger Range, Montana: relationships of pocket gophers (Thomomys talpoides) to time of snow melt. M.Sc. Thesis. Bozeman, Montana: Montana State University. 26 p.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.