Montana Field Guide

PLANTS: A mat-forming perennial plant that grows from an intricately branched caudex. Hairs on plant are strigillose (stiff, straight, sharp, and appressed) to villous (long, soft, crooked, and not tangled). Stems prostrate with upper ends ascending 1–3 cm. Source: Lesica et al. 2012.

LEAVES: Leaves alternately arranged on the stem and pinnately divided into 3 to 7 leaflets. Leaflets are narrowly lanceolate in shape, 3–9 mm long, and with mucronate tips. Terminal leaflet is confluent with the rachis of the leaf. Stipules are 2–5 mm long, sessile (basally fused). Source: Lesica et al. 2012.

INFLORESCENCE: Raceme of 1 to 3 flowers growing in the axils of a leaf and shorter than the leaves. Papilionaceous flowers: Petals are white to purple; Banner is reflexed, 4–8 mm long; and Keel is 3–7 mm long. Sepals are green with white and/or black strigillose hairs, 1-3 mm long. Legume is ovoid, compressed, strigose, and 3–5 mm long. Source: Lesica et al. 2012.

In Montana we have two varieties: kentrophyta and tegetarius (Lesica et al. 2012).

Astragalus is derived from the Greek word for ankle bone, astragalos which may refer to the shape of the leaves or fruits (legumes) (Giblin et al. [eds.] 2018).

At the species-level Astragalus kentrophyta is unique in having a combination of these characteristics:
*Height: Grows low along the soil; mat-forming.
*Leaflets: 3-9mm long and tipped with an abrupt, short, sharp, and terminal tip (mucronate). Terminal leaflet is confluent (continuous) with the rachis.
*Inflorescence: 1-3 flowers

Variety kentrophyta

Variety tegetarius

Stony or gravelly, sparsely vegetated soil of grasslands, steppe, and fellfields in the plains, valleys, and alpine zones of Montana (Lesica et al. 2012).

POLLINATORS
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus appositus, Bombus auricomus, Bombus bifarius, Bombus borealis, Bombus centralis, Bombus fervidus, Bombus flavifrons, Bombus huntii, Bombus mixtus, Bombus nevadensis, Bombus rufocinctus, Bombus ternarius, Bombus terricola, Bombus occidentalis, Bombus pensylvanicus, Bombus griseocollis, and Bombus insularis (Macior 1974, Thorp et al. 1983, Mayer et al. 2000, Colla and Dumesh 2010, Wilson et al. 2010, Koch et al. 2012, Miller-Struttmann and Galen 2014, Williams et al. 2014).

Plants reproduce by seed. Seeds have the potential for long term viability in natural seedbanks (Tara Luna personal communication). In eastern Glacier County it has been observed that plants do not flower and reproduce during drought conditions (Tara Luna personal communication).

PAPILIONACEOUS FLOWER
*Species belonging to the Pea Subfamily (Papilionoideae) have papilionaceous flowers (Elpel 1998). This applies to almost all species in the northern latitudes (Elpel 1998).
*It refers to the petals of the flowers appearing like a butterfly.
*The 5 petals (collectively called the corolla) have a bilateral symmetry: large upper petal (banner), two lateral petals (wings), and usually two fused lower petals (keeled). The keel petals resembling a boat.

GRAZING
In north-central Montana, livestock have been observed to avoid plants.