Glabrous and glaucous, taprooted biennial. Stems erect, usually branched, 20–80 cm. Basal leaf blades oblong, 1–10 cm long, entire. Stem leaves sessile to short-petiolate, reduced, lanceolate. Petals white to purple, 4–7 mm long. Fruits ascending, 1–3 cm × 0.7–1.1 mm; the stipe 0.3–2 mm long; style 0.4–1.3 mm long; pedicels ascending, 2–8 mm long. Plants in Montana are variety
integrifolium (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Differentiating Montana's three
Thelypodium species requires a technical key, such as those by AL-Shehbaz
in FNA 2010, Lesica et al (2012), and Giblin et al. [eds.] 2018. Other genera can also appear similar.
Thelypodium species have cylindrical siliques while species of
Arabis have flattened siliques.
Entire-leaved Thelypody -
Thelypodium integrifolium subspecies
integrifolium* Stem Leaf: Bases are cuneate to attenuate, not auriculate, sagittate, or auriculate clasping; sessile.
* Flower: Petals white to purple, 4-7 mm wide
* Fruit: Siliques ascend, 1-3 cm by 0.7-1.1 mm long with a 0.3-2.0 mm long stipe.
* Habitat: Moist to wet, alkaline or saline meadows in the plains, valleys, and montane zones of Montana.
Northwestern Thelypody -
Thelypodium paniculatum, SOC
* Stem Leaf: Auriculate-clasping, mostly sessile.
* Inflorescence: Terminal racemes do not considerably elongate in fruit (opened flowers crowded at tip).
* Flower: Petals lavender to purple, 2.5-5 mm wide. Anthers 1-2 mm long.
* Fruit: Siliques often straight, 1.3-2.3 mm wide.
* Seed: Plump.
* Habitat: Wet meadows and streambanks. In the montane zone of Montana.
Slender Thelypody -
Thelypodium sagittatum subspecies
sagittatum, SOC
* Stem Leaf: Auriculate-clasping, mostly sessile.
* Inflorescence: Terminal racemes do not considerably elongate in fruit (opened flowers crowded at tip).
* Flowers: Petals light to deep violet-purple, 1-3 mm wide. Anthers 2-3 mm long.
* Fruit: Siliques often straight, 0.5-1.2 mm wide.
* Seeds: Flat.
* Habitat: Moist, often alkaline meadows that dry by summer, desert plains to lower mountains. In the montane zone of Montana.
