Mosquito Range Mustard

This plant is a perennial herb growing about six inches tall and bearing clusters of cream-white flowers in the summer. The alpine habitat of the plant is a wet tundra kept constantly fed with ample water by the surrounding snowfields. Wind melts the snow which runs into the tundra and turns it to a fen, a wetland on limestone substrates. The plant grows in rocky nooks that shelter it from the wind and keep the mossy peat soil saturated, but not flooded. The elevation is at least 3700 meters. The habitat is within a section of the Continental Divide that trends east–west in opposition to the general north–south direction of most of the ranges, and the plants grow on south- and east-facing slopes. There are about eleven occurrences, with populations at Hoosier Ridge, Mount Silverheels, the Mosquito Pass, the Hilltop Mine, Mount Blue Sky, and Loveland Mountain. The total area occupied by the plant is probably around 500 acres (2.0 km2).

This plant is the only Eutrema in the lower 48 states and only one of two that occur in North America; its nearest close relative is Eutrema edwardii, a plant of the Arctic. E. penlandii is a small alpine climate species, possibly a relict from the last ice age which persists in the high, cold fens of the Rocky Mountains. Today the plant only occurs in the Mosquito Range, a ridge of mountains in the Rockies. It was first collected by the botanist C. William Penland in 1935 on Hoosier Ridge in the Mosquito Range, and it is one of several rare alpine plants native to the area, such as the globe gilia (Gilia globularis).