Northwestern Thelypody - Thelypodium paniculatum
Thelypodium sagittatum var. crassicarpum
State Rank Reason (see State Rank above)
Known only from an 1899 collection in Beaverhead County, although Dorn (1984) also reports it for Madison County.
Northwestern thelypody is an herbaceous biennial or short-lived perennial with solitary, simple or branched stems that are 3-7 dm high and arising from a taproot. Its lower leaves are 4-10 cm long and have petioles and narrowly lance-shaped, entire-margined blades. The upper stem leaves are 2-6 cm long and lance-shaped with basal wings that clasp the stem. Foliage is glabrous and has a thin, waxy coating. Flowers are borne on ascending stalks in cylindric inflorescences that are up to 35 cm long when mature. Each flower has 4 separate sepals that are 5-8 mm long, 4 separate, lavendar petals that are 10-16 mm long and 2-6 mm wide, and 4 long and 2 short stamens. The ascending, straight, cylindrical capsules, or siliques, are 25-40 mm long and 1.3-2.3 mm wide.
Flowering occurs in June.
Thelypodium sagittatum is very similar but has petals that are only 1-3 mm wide and fruits that are less than 1.3 mm wide.
This species is known from ID, MT, WY and CO (Kartesz in prep. 2012). It occurs in eastern ID, southwestern MT, in Beaverhead County (Montana NHP 1999) but evidently not Madison County as included by Dorn (1984); western and southern WY in 8 counties (Park, Teton, Sublette, Lincoln, Uinta [T. paniculatum type locality], Fremont, Carbon and Platte),and CO Jackson County (Weber and Wittmann 1996a) and perhaps the northwest in Moffat County (Colorado State University Herbarium 1999, but not Weber and Wittmann 1992, 1996b).
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)
Northwestern thelypody grows in wet sedge meadows where the water level may cover basal portions of the plant. It appears to favor meadows and stream bottoms that remain wet for most of the season. Two localities in Yellowstone National Park are in very wet sedge meadows. In contrast, Thelypodium sagittatum, grows in alkaline meadows that are often dry, but may be wet in the early part of the season (Al-Shehbaz 1973).
Ecological Systems Associated with this Species
Northwestern thelypody has lightweight seeds that are probably very easily distributed (Al-Shehbaz 1973). Wind may be an important factor in their dispersal in open habitats such as deserts, flats and open slopes, but the action of rain wash is perhaps equally if not more important (Al-Shehbaz 1973). Flooding is likely to be a major means of seed dispersal for species growing along streamsides, creek beds and river banks, and may also be important for those found in meadows (Al-Shehbaz 1973).
Based on available habitat information, this species could be vulnerable to riparian grazing or hydrologic changes.
- 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.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.