Potentilla hickmanii

Species of flowering plant

Potentilla hickmanii (called Hickman's potentilla or Hickman's cinquefoil) is an endangered perennial herb of the rose family. This rare plant species is found in a narrowly restricted range in two locations in coastal northern California, in Monterey County, and in very small colonies in San Mateo County. This small wildflower, endemic to western slopes of the outer coastal range along the Pacific Ocean coast, produces bright yellow blossoms through spring and summer. This species was formerly thought to be growing in Sonoma County, but that population has been recently reclassified as another species, Potentilla uliginosa, and is presumed extinct in that county. This plant, along with many other threatened species in the northern California Floristic Province, has been designated as a species meriting protection by the U. S. government, state of California, local governments, and private conservation groups. These designations have led to blueprints for protection of Hickman's potentilla in the form of official endangerment classifications and a species recovery plan, the latter promulgated by the U. S. Fish and Wildlife Service.

P. hickmanii is a long lived, rosetted, nonglandular flowering plant with a thick taproot. The stem is prostrate, long. The somewhat subglabrous leaves are pinnately compound into generally six paired, palmately cleft leaflets. These basal leaves range from in length The Monterey population is within the municipal boundaries of the city of Monterey, growing in a native grassland opening of the Monterey pine forest at an old summer camp site. Plantings have been made, as attempts to establish new colonies in Monterey County at two areas the Point Lobos State Reserve, but those plantings failed by the summer of 2011 from the invasion of European weed grasses, and by the plantings situated too far from where the plants could easily be monitored or managed, and by planting in one site that was too wet for the species to survive. Another coastal colony was discovered in Moss Beach, California, in 1933 in a wetland area at the mouth of San Vicente Creek; this colony was presumed extinct by at least the 1970s. Another population in San Mateo County was discovered in 1995 on the south slopes above Martini Creek (USGS quad reference Montara Mountain 3712254), on private land by biologists conducting surveys for the Devil's Slide highway project. In all cases, the populations are found between 10 and 135 m above sea level. The habitat for this species includes native grassland meadow openings in pine forests, coastal bluff native perennial grasslands, and under pine trees in duff. The key to the habitat for this species is the decomposed granite substrate that lies directly under the very fine grained grassland topsoil.

The Monterey Peninsula, discovery site of P. hickmanii, is in a native grassland opening within the Monterey pine forest. The peninsula is influenced by a marine climate that is pronounced due to the upwelling of cool water from the Monterey submarine canyon. Rainfall is 40 to 50 cm per year, but summer fog drip is a primary source of moisture for plants that would otherwise not be able to persist with such low precipitation. Some taxa, such as the coastal closed cone pines and cypresses are relict stands, e. g. species that once extended more widely in the mesic climate of the late Pleistocene period, but then retreated to small pockets of cooler and wetter conditions along the coast ranges during the hotter, drier early Holocene period between 6000 and 2000 BC. Alice Eastwood discovered P. hickmanii in 1900 on the Monterey Peninsula, a region then considered the fringe of civilization. The Big Sur wilderness lay just beyond, unpenetrated by any roads at that time. Eastwood, curator of botany at the California Academy of Sciences in San Francisco was a pioneer biologist in exploring this remote area. On an expedition to amass specimens of rare plants from this southern reach of Monterey County, she retrieved a specimen of this previously unrecorded plant and named this species after J. B. Hickman. Hickman was her guide on that collecting trip, and was the horticultural commissioner of Monterey County.

Update (2013) on populations in San Mateo County, Montara Mountain, north of town of Montara: Specific consistent counts of this species are difficult due to the low stature, extended flowering period, and difficult terrain, making year to year comparisons problematic. The 2013 surveys have clearly shown that population 4 still exists above the existing Harding grass invasion, with at least 500 plants found in this area. In 2014, hand weeding of the area around population during summer 2011 has significantly lowered the weed plant cover of the area, with the big rattlesnake grass (Briza) originally at 61% cover in 2011 is now down to 1% cover in 2014. The hillside of Harding grass where population 4 exists was mowed in summer 2014.