Montana Endemic: Physaria humilis - St. Marys Peak Bladderpod

Montana Endemic: Physaria humilis – St. Marys Peak Bladderpod

Radd Icenoggle

March 19, 2023

Botanizing

Physaria humilis - A Bitterroot Endemic

As the snow continues its slow recession with the coming of spring, our thoughts drift more and more toward the hiking and botanizing that is just around the corner. I got to thinking about the rare plants that I want to find this summer season, and I recollected back to some of the rarities I have been lucky enough to find. And one of the best of these rare plants is the Physaria humilis, the St. Marys Peak Bladderpod.

Physaria is a genus of flowering plants in the family Brassicaceae (mustards). Many species are known generally as twinpods, bladderpods, or lesquerella. They are native to the Americas, with many species endemic to western North America. They are densely hairy annual and perennial herbs often growing prostrate or decumbent, along the ground in patches or clumps. They bear inflorescences of bright yellow flowers. The fruit is often notched deeply, dividing into twin sections, giving the genus its common name of twinpod.

This Montana endemic is restricted to a very small area of the Bitterroot Mountains in the vicinity of St. Marys Peak with only a few known occurrences. Endemism refers to the occurrence of a particular species in a specific geographic area and nowhere else in the world. Endemic plants are often rare and threatened due to their limited distribution and vulnerability to environmental disturbances. As a result, there is a strong correlation between plant endemism and rarity, with many endemic plants being classified as endangered or critically endangered. Conservation efforts are essential to protect these unique and rare species, as they are often key components of their ecosystems and play important ecological roles. So when searching for Physaria humilis, it is critical to remain on the trail that leads to the summit of St. Marys as trampling is a key concern in the conservation of this plant.

Description

Physaria humilis is a small, low perennial with 1 to several unbranched stems that are 2-5 cm long and arising from a simple taproot covered with old leaf bases. The basal leaves are 2-5 cm long and have entire-margined, ovate, or elliptic blades and a long, narrow petiole. The 3-6 stem leaves are spoon-shaped and 3-7 mm long. The herbage is silvery with a dense covering of appressed, branched hairs. The small, terminal inflorescence is 3-5 flowered, and the four yellow petals are 7-9 mm long. The compressed fruits (properly called siliques) are 3-4 mm long, and wider than they are long. It flowers once the snow has melted from the wind-scoured slope of the peak.

History

Physaria humilis (originally known as Lesguerella humilis) was formerly described as a species in 1984 by Dr. Reed Rollins. It was first discovered on St. Joseph Peak in the Bitterroot Range in 1966, by Klaus H. Lackschewitz and Tor Fageraas. This first specimen, and other early collections, were variously labeled as Lesguerella alpina, Physaria didvmocarpa, or P. geveri, but Rollins ultimately determined that they represented a previously undescribed species. The type specimen was collected in 1983 by Reed C. and Kathryn W. Rollins, with Lackschewitz, Peter Lesica, and Aileen G. Roads, near the summit of St. Mary Peak, also in the Bitterroot Range.

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Botanizing