Packard’s milkvetch Astragalus cusickii packardiae
ESA status: candidate for listing

This species has been awaiting Endangered Species Act listing for
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Packards milkvetch pc Ann Debolt

Packard’s milkvetch is considered one of the rarest plants in Idaho. It is so rare that it was only discovered in 1980, and there are only a few years of monitoring data available for known populations. There are approximately 5,000 plants located on 10 square miles of rolling hills and terraced creek bottomlands in southwestern Idaho near the town of Payette.

Packard’s milkvetch is a narrow endemic restricted to visually distinctive light-colored sedimentary outcroppings, where the soil properties appear to differ from the surrounding soils in ways that are not yet understood. Adapting to the unique soil composition probably allowed the milkvetch to avoid competition from other native plants, and also makes their environment more resistant to weed invasion.

The plant’s unique habitat patches, historically within sagebrush steppe, are now surrounded by annual grassland dominated by non-native species. While livestock grazing, unnatural fire and invasive plants continue to degrade the landscape, the biggest threat to the milkvetch is off-road vehicles (ORVs).

In 1999, when the first survey of the milkvetch was taken, ORV use was likely contained in the nearby Clay Peak Motorcycle Park, and no sign of ORV use was discovered in the plant’s habitat. But that quickly changed. The motorcycle park closed in 2007, and ORVs began running rampant over nearby public land, with devastating effects on the millkvetch. In 2009, over half the monitoring plots had ORV tracks running through them. ORVs crush and uproot the plants and spread invasive weeds. They also disturb the unique soils that the milkvetch needs, leading to accelerated erosion of its steep outcroppings. The erosion exposes the milkvetch’s roots, smothers them in loose soil, and hinders seed germination. The Bureau of Land Management has proposed to designate an Area of Critical Environmental Concern for the plant, which would implement new management for ORVs. However, the designation has not yet been adopted, and the ORVs keep coming. There is no fencing, no signage, and no enforcement, even in the one area where ORV use is supposedly limited to existing roads and trails.

Packard’s milkvetch needs immediate protection from ORV use. The riders and their thrill machines, if left unchecked, could crush one of our rare native plants into oblivion. WildEarth Guardians is fighting to make sure this tragedy is not allowed to happen.

photo credit: Ann Debolt