Montana Field Guide

Taper-tip desert-parsley is a low, herbaceous perennial with stems reaching 7-25 cm in height and bearing 1-2 nearly prostrate leaves on the lower portion. The leaf stalks form a sheath around the stem and the blades are broadly lance-shaped (2-11 cm long) and 3-4 times divided into oblong-linear segments, each 2-5 mm in length. The foliage is roughened like sandpaper. Tiny yellow flowers are borne atop the stems in 5-8 open, umbrella-like clusters with stalks 1-5 cm in length. Each cluster is subtended by up to 6 pointed, linear, inconspicuous bracts, or involucels. Flowers have 5 separate petals atop an ovary that matures into a glabrous, elliptical, flattened fruit 5-8 mm long with corky wings (about. 0.5 mm wide) and a stalk that is 3-10 mm long.

Flowering occurs in June and fruits mature in July.

The closely related Lomatium cous has conspicuous elliptic involucel bracts and fruit stalks that are only 1-3 mm long.

The taper-tip desert-parsley grows in scree or dry, gravelly soil of south- or west-facing slopes in mountains, canyons and foothills (Vanderhorst and Heidel 1998). Subsurface horizons often have clay or silt accumulations, or the gravels are perched on shallow bedrock, ameliorating the droughty surface conditions. Most populations are on limestone, but the species has also been found on igneous rock.

In Montana, populations of the species typically occur on dry, unstable, moderate to steep, south- or west-facing slopes in mountains, canyons and foothills (Vanderhorst and Heidel 1998). Its position on the slope varies with substrate conditions. The steepest slopes are in canyons, formed from colluvium of overtowering cliffs. Rock outcrops are present at nearly all sites. A few populations (e.g., near Bannack) extend onto nearly level ridgetops with shallow gravels overlying bedrock. Some large populations extend onto more mesic northern exposures and canyon bottoms or toeslopes.

Soils are generally poorly developed lithosols with a high proportion of gravel, commonly referred to as scree (Vanderhorst and Heidel 1998). The substrates are dry, loose, easily disturbed, and have high water infiltration rates with little or no surface runoff. Surface horizons may be sandy, but subsurface horizons often have clay or silt accumulations, or the gravels are perched on shallow bedrock, ameliorating the droughty surface conditions.

Most populations in the state occur on substrates with limestone parent material but it also grows on igneous substrate in the Tendoy Mountains and Grasshopper Creek and Cold Spring Creek drainages. In Wyoming, this desert-parsley is most often found on volcanics (W. Fertig, personal communication).

A deep, tough rootstock and short period of active growth allow the species to exploit seasonal subsurface moisture, avoid damage from shifting scree, and remain dormant in dry years. Most populations occur on sites with warm, southerly aspects. By mid-summer, the exposed scree is dry and hot, and leaves and stems of the plants are withered. Year to year climatic fluctuations undoubtedly affect seed production, with apparently greater seed production in cool, wet years. In dry years, a high proportion of the plants may remain in a vegetative (non-flowering) state.

In general, the rugged topography and lack of forage in taper-tip desert-parsley habitats minimize direct threats from livestock grazing and other disturbance.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Taper-tip Desert-parsley are currently assigned as unknown (MTNHP Threat Assessment 2021). Spotted Knapweed (Centaurea stoebe), and Cheatgrass (Bromus tectorum) are found at some populations. Information about the severity of impacts to populations is needed to assess its relative risk.