Montana Field Guide

PLANTS: A rhizomatous shrub that grows 20-80 cm tall, but can experience die-back. Simple to sparingly branched stems grow erect to ascending. Plants have soft, interwoven hairs (tomentose), but become less hairy (glabrate) with age; this can give the plant a hoary appearance. Sources: Lesica et al. 2012; McGregor et al. 1986.

LEAVES: Alternately arranged on the stem. Leaves have short petioles and are pinnately-divided into 13-21 mm leaflets. Leaflets are oblong, 8-15 mm long with smooth (entire) margins, and covered with soft, short, grayish-white hairs (canescent). Sources: Lesica et al. 2012; McGregor et al. 1986.

INFLORESCENCE: Violet flowers are arranged in racemes that appear like a spike. Narrow, racemes are 7-15 cm long, arise from leaf axils, and are subtended by pubescent bracts. Collectively, sepals (calyx) are cone-shape (obconic). The 5 sepals are 3.5 mm long with sessile glands and dense hairs. The single petal is reduced to the banner, 4-6 mm long, and encloses the stamens. Stamens are 10, orange, united at their base, and extend beyond the petal. Pistil is single and superior. Fruit is a 1-seeded legume, 3-4 mm long, canescent with sessile glands, and has a long beak. Sources: Lesica et al. 2012; McGregor et al. 1986.

Flowering from late June to mid July; fruiting through summer.
Plants found in Carter County during August 2019 were mature and in flower and producing seed (Hansen 2019).

Dalea and Psoralea have similar looking leaves, but plants are herbaceous with flowers that have more than one petal.

Montana has several woody plants in the Pea or Fabaceae family:

Lead Plant - Amorpha canescens, Native, SOC
*Habit: Relatively shorter shrub.
*Leaves: Pinnately divided with more than 10 leaflets.
*Hairs: Short, dense, and whitish-gray (canescent).
*Flowers: Corolla consists of 1 violet petal reduced to a banner.

Siberian Pea Tree - Caragana arborescens, Exotic
*Habit: Highly branched, medium to tall shrub.
*Leaves: Even-pinnately divided 4-10 leaflets.
*Hairs: Pubescent.
*Flowers: Yellow with 4 petals, papilionaceous.

Scotch Broom - Cytisus scoparius, Noxious
*Habit: Medium to tall shrub.
*Leaves: Pinnately divided with 1-3 leaflets.
*Hairs: glabrous to pubescent.
*Flowers: Bright yellow with 4 petals, papilionaceous.

Black Locust - Robinia pseudoacacia, Introduced
*Habit: Trees up to 20 meters tall.
*Leaves: Odd-pinnately divided with 9-17 leaflets.
*Hairs: Sparse hairs (puberulent) to nearly hairless (glabrate).
*Corolla consists of 1 violet petal reduced to a banner.

In Montana plants occur in grasslands and woodlands where soils are often sandy soil within the Plains zone (Lesica et al. 2012).

Based on the 2019 observations, Lead Plant was found at elevations ranging from approximately 3,960 to 4,080 feet on slopes ranging from 5 to 40 percent (Hansen 2019). The ridges have soils consisting of mixed sands and gravels mainly in the Reeder-Cabba loams 4-15% slopes, Belltower-Dast-Reeder complex 15-35% slopes, and little bit in Parshall-Cohagen fines sandy loam 4-15% slopes (Hansen 2019).

POLLINATORS
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus pensylvanicus and Bombus griseocollis (Colla and Dumesh 2010).

LAND USE
In the Great Plains, Lead Plant is one of the most palatable range plants (McGregor et al. 1986). Plants decrease with grazing, becoming rare in overgrazed habitats (McGregor et al. 1986). In pastures and meadows where it is mowed, plants grow as herbaceous perennials, but in undisturbed grasslands plants can become tall shrubs (McGregor et al. 1986).

Plants found during 2019 in Carter County were growing within grazing allotments that have been in effect for many decades (Hansen 2019). At the time of the August observations cattle were not present and no grazing of the plants was observed. All sites had burned in the 1988 Brewer Fire with moderate-high intensity and also in the 2002 Kraft Springs fire with low-moderate intensity (Hansen 2019). The sites are naturally regenerating with Ponderosa Pine (Pinus ponderosa); one site is being colonized by Quaking Aspen (Populus tremuloides) which seem to be recently expanding in the Long Pines area southeast of Ekalaka, Montana (Hansen 2019).

STATE THREAT SCORE REASON
Reported threats to Montana’s populations of Lead Plant include the presence of noxious weeds, but the impact was found to be negligible, which results in an unassigned State Threat Score (MTNHP Threat Assessment 2021).