Yellowstone National Park is like no other place on Earth. Protected here are the largest concentration of geysers in the world, a spectacular array of free-roaming wildlife, and a collection of rare and unique plant species. Yellowstone sand verbena (Abronia ammophila) is one such special plant. Unique to Yellowstone’s lakeshores, this sand verbena is endemic to the park—it exists nowhere else in the world.

The presence of a sand verbena on the Yellowstone Plateau is surprising because of the high elevation (approximately 7,740 feet, or 2,360 meters) and long, cold winters. Yellowstone sand verbena is a member of a New World plant family that typically lives in warmer climates such as deserts and tropical areas. The genus Abronia includes about 30 species that primarily occur in warmer areas of the western United States and Mexico. Some botanists speculate that the thermal activity in Yellowstone has made it possible for a sand verbena to survive the harsh winters here and slowly evolve into a species that is adapted to this climate.

In recent surveys, botanists have located four populations of Yellowstone sand verbena, but very little is known about its life history and biology. For example, the plant is represented as an annual in the scientific literature, although it is actually a perennial that overwinters underground as a large root system. No one currently knows how the plant is pollinated, how the seeds are transported, or how long the seeds survive. In order to protect this unusual sand verbena, more research is needed to better understand this remarkable plant.

What it Looks Like

Yellowstone sand verbena, as the name suggests, is associated with sandy sites. It grows as a sand-hugging mat one to four inches tall and up to three feet wide. Because sticky glands cover the surface of the plant, sand grains adhere to flowers, stems, fruit, and leaves.

Clusters of white flowers are present from mid-June to late August or early September when harsh frost kills the above-ground parts of the plant. This long blooming period is unusual for Yellowstone; most plants bloom for a short time during the summer. The advantages to the sand verbena for this sustained bloom are unknown, although one reason could be the sporadic presence of pollinators such as moths. A prolonged blooming period would maximize the chance that at least some of the blossoms will be pollinated.

Where it Grows

Frank Tweedy, who wrote the first flora of Yellowstone, first collected Yellowstone sand verbena in 1885. To date, it has only been found around Yellowstone Lake and is restricted to stabilized sandy areas just above the maximum splash zone. Yet herbarium specimens suggest that the species used to be more widely distributed along the lake’s shoreline than it is today. Yellowstone sand verbena is sensitive to disturbance, such as trampling, and increased visitor use of the lakeshore may have contributed to its decline. The entire population of Yellowstone sand verbena numbers approximately 8,000 individuals, which vary in size from seedlings to large mats.

Why it's Important

For many people, the beauty of a plant growing in its natural habitat is enough reason for it to be valued. Beyond that, Yellowstone sand verbena occupies a specific niche in the unique, high-elevation, thermally influenced lakeshore community. The inter-woven relationship of the plants and animals in this community is not yet fully understood. The loss of any part of this web of life could have far-reaching consequences.

Just like many other native plant species, very little is known about the life history and biology of Yellowstone sand verbena. Botanists want to understand how this unique species with its highly restricted distribution evolved in the Yellowstone ecosystem, and what the relationship of Yellowstone sand verbena is to other sand verbenas, especially those in the northern Rocky Mountain region.

Scientists do not yet know if the genetic or chemical makeup of this particular plant will be useful to humans. In recent years, important medical treatments have been derived from little-known plants, such as the rosy periwinkle (which contains compounds that are the best-known treatment for childhood leukemia) and the Pacific yew (which contains taxol, the best hope for treatment of ovarian cancer). Yellowstone sand verbena, as long as it is continually protected in the park, will remain available for future research and also for everyone to enjoy.

There are three publication-quality Sand Verbena images available online:

Yellowstone National Park gratefully acknowledges the financial assistance of Canon USA through the “Eyes on Yellowstone, made possible by Canon” program administered by the Yellowstone Park Foundation and of the National Fish and Wildlife Foundation. This support is enabling botanists to collect information about the Yellowstone sand verbena so that you can learn more about one of Yellowstone’s rare endemic species.

For more information contact Yellowstone Park at (307) 344-7381.