Showy Indian Clover Reintroduction Project

Photo Credit: FWS

By Mike Hawkes

The showy Indian clover (Trifolium amoenum), a tall native annual, is an endangered wildflower that was once widespread in coastal grasslands within the counties surrounding San Francisco Bay, California. In 1994, after almost all known populations were extirpated due to habitat loss, the Fish and Wildlife Service listed this species as endangered. The single remaining wild population grows in the front yard of a private residence in coastal Marin County. But in July 2006, Diana Immel (a rare-plant ecologist) and the Service’s Sacramento Field Office reintroduced the showy Indian clover to Point Reyes National Seashore (PORE) in Marin County, California.

We took this step toward the species’ recovery in coordination with the National Park Service, which manages PORE. The reintroduction will reduce the risk of extinction by spreading populations over additional locales that are protected in perpetuity on public land.

Showy Indian clover habitat.

Photo Credit: FWS

The reintroduction site at Point Reyes, known as D Ranch, is undisturbed coastal prairie with soils and plant communities similar to the adjacent E Ranch, where J. Burtt Davy collected the species in 1900. In the fall of 2006, we planted handprepared seeds in small groups along 12 transects following environmental variables (aspect, elevation, moisture) at six different locations spread over a wide area. A monitoring trip in June 2007 revealed that over half of the 728 planted seeds germinated. The rest were eaten by snails, insects, and possibly small mammals. Other plants were eaten later by larger mammals, such as rabbits, gophers, deer, and elk. Plants that survived herbivory were subject to desiccation due to low rainfall.

Seventy-seven plants survived to the end of the growing season, and all but one of those produced flower heads. Although seeds had not completely developed by the time of our monitoring visit, we estimated future seed production using data from a previous study. Over half of the expected seed production (449 seeds) was expected from one area (transect 9) that differed from the other transects by having a relatively higher elevation and a gentler slope.

Rare-plant ecologist Diana Immel examines a showy Indian clover bloom.

Photo Credit: FWS

A second year of funding in Fiscal Year 2008 enabling Ms. Immel another year of monitoring at PORE. Germination was extremely low in winter 2007/2008 and, by June 2008, only transect 9 produced plants with flowers. In October 2008, she returned to the site to conduct supplemental seeding at seven of the most successful transects. Though rainfall was low in early winter 2008/2009, February 2009 has so far proved normal to above average in that regard, providing hope for improved 2009 seed set. Also, as Trifolium amoenum seeds can remain viable in the soil for many years, any seeds that do not germinate this year have the potential to contribute both genetically and numerically to the population in the future. Monitoring for flowering plants and estimated seed set is planned for approximately May 2009, at which point future actions will be determined.

This was intended as a pilot project to determine microhabitats most suitable to Trifolium amoenum survival and seed production. The project may gain additional funding in future years to supplement the existing seedbank at sites where fitness was highest. Its true success will be revealed in the next few years when we can more accurately determine the additional contributions to the seedbank and resulting germination rates. The project, funded by the Service’s Sacramento Fish and Wildlife Office, exemplifies a mutually beneficial partnership with the National Park Service.

We hope that with refined site selection and more typical rainfall, the populations of this endangered plant will flourish.

Valary Bloom, a fish and wildlife biologist in the Service’s Sacramento Fish and Wildlife Office, can be reached at valary_bloom@fws.gov or 916-414-6600.