Montana Field Guide

Dense-leaf Draba is a mat-forming perennial with leaf rosettes at the ends of numerous rootcrown branches, which are clothed with old leaf bases. The leafless stems are 3-15 mm high and arise from some of the rosettes. The fleshy, narrowly lance-shaped leaves are 2-12 mm long and have a prominent midvein and straight, unbranched hairs on the entire margins but are otherwise mostly glabrous. 3-15 stalked flowers are borne at the tops of the stems. Each flower has 4 separate sepals, 4 separate, yellow petals that are 2-6 mm long, and 4 long and 2 short stamens. The style is 0.5-1.0 mm long. The hairy, egg-shaped capsules are 2-7 mm long and are borne on erect or ascending stalks.

Flowering from May-July, depending on elevation.

There are many similar-appearing, yellow-flowered, mat-forming species of Draba in our area. A technical manual and hand lens or microscope is required for positive identification. This species can be dintinquished from D. oligosperma by the simple hairs. Draba daviesiae also has glabrous leaves, except for simple hairs on the margins, but it has glabrous fruits.

Gravelly, open soil of rocky slopes and exposed ridges in the montane to alpine zones.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Dense-leaf Draba include impacts from multiple land-use activities as its habitat spans moderate to high elevations (MTNHP Threat Assessment 2021). Populations scattered from grasslands to rocky ridgelines are exposed to livestock grazing and trampling, roads and highways, and recreation-related trampling from hikers, climbers or off-highway vehicle (OHV) users. Encroachment of noxious weeds is reported to threaten some populations, where a risk of chemical herbicide application is also a potential concern.