Plants

Cape ivy control

Cape Ivy is the California coast's biggest and baddest weed. If the Park Service had their way, we would be circulating a mug shot of this bright green vine. It is such a pain that it is the first wildland weed that the California Department of Agriculture has decided to develop a biocontrol for, it has cost so much money for land management agencies to combat it. Cape ivy currently covers 500,000 acres throughout the state! Golden Gate preserves some of the only remaining high quality coastal habitat in the country. Conservation International and The Nature Conservancy consider the California Floristic Province to be a global biodiversity hotspot: one of 25 regions worldwide where biodiversity is most concentrated and the threat of loss most severe. The San Francisco Bay area is also a United Nations Biosphere Reserve, one of 400 sites worldwide where governments, scientists, and NGOs are working together to protect critical ecosystems.

Cape ivy was introduced to the eastern United States in the 1850s as a common house plant. It's pretty yellow flowers are proof positive that looks can kill. It was introduced to California a century later in the 1950s. It is a now a serious threat to most of the western coast of North America as well as Italy and Australia. In its natural range in South Africa, Cape ivy has a relatively restricted distribution, growing in moist mountain forests. Central coastal California shares a Mediterranean climate type with only four other regions in the world: South Africa, the Mediterranean basin of Europe, Western Australia, and Chile. Crossing the world's oceans from continent to continent through the movements of mankind, these plants have landed in areas that they never would have been able to breach on their own.

In Golden Gate National Recreation Area cape ivy has invaded disturbed sites with year-round moisture, including riparian habitats along stream banks, coastal forests, and soils with a high water table. The ivy is also very good at colonizing new areas due to the fact that it can reproduce from stem fragments as small as half an inch. Carried by runoff, wildlife, or humans, it can root and grow rapidly. To illustrate the point, in 1987 there were 9 acres of Cape ivy in the Marin Headlands. In the next decade, the ivy gobbled up 67 acres! The ivy forms impenetrable mats as it climbs native shrubs and trees to form a solid layer that blocks out light and smothers other vegetation. It drapes from tree to tree, aptly nicknamed the "kudzu of the west."

Cape ivy is unsuitable forage for most wildlife due to the presence of strong chemical compounds (alkaloids and xanthones) in its leaves. It is known to be toxic to mammals and spiders, and there is some evidence that it is harmful to aquatic organisms. This monoculture of a bully plant reduces habitat for pollinators, and drastically alters bird diversity. Cape ivy most likely alters ecosystem level functions like nutrient cycling and food web dynamics as well.

Currently Golden Gate and Point Reyes National Seashore to our north are working together to remove 188 acres of ivy patches in both parks. The basic plan is to first create containment lines around the patches to stop the spread. Then all vegetation in the patch must be completely removed and raked to bare ground, and tarped to compost on site. Native shrubs and trees will resprout and refill the area over time, with staff consistently following up on ivy resprouts for the next 3-5 years. Different methods have been used in removal, mainly manually or with power tools, but also employing judicious herbicide application and innovative methods such as goat grazing and prescribed fire. Staff have also monitored different treatment plots and mapped ivy areas to be contained or removed in the future.

Nonnative Plants

Nonnative plants thrive in the park, particularly in areas subject to intensive historic land use related to grazing or military occupation, or adjacent to urbanized areas that are a constant source of weed invasion. The spread of non-native plants represents the most significant threat to the biodiversity of the park. One or several of the park’s 21 most invasive non-native pest plant species invade approximately 85 percent of the park’s estimated 48 plant communities. Research has shown that introduced species alter community composition and reduce the diversity of native plants, insects, and small mammals. Invasive non-native species are also found within all nine Special Ecological Areas designated as the most biologically intact and diverse areas within the Golden Gate. Non-native species also directly threaten habitat for the federally endangered mission blue and San Bruno elfin butterflies, Raven’s manzanita, Presidio clarkia, and San Francisco lessingia, as well as 12 other special status plants (Department of Fish and Game and Native Plant Society listed).

Golden Gate has currently targeted the 22 most invasive non-native species for control. These species include: Monterey pine, blue gum eucalyptus, Monterey cypress, black acacia, thoroughwort, cotoneaster, helichrysum, Himalayan blackberry, tall fescue, European harding grass, French and Scotch broom, Cape ivy, Ox-eye daisy, pampas grass, yellow star thistle, periwinkle, gorse, capeweed, English ivy, and calla lilies. These invasive plant populations are considered under control due to a decade of volunteer, staff and grant expenditures. And despite the extensive urban perimeter around the park, only two new invasive species have established small populations within the park within the last decade.

Endangered Scrubland Plants

The endangered Raven's manzanita is one of the San Francisco peninsula's unique subspecies of Hooker's manzanita. Discovered by Missouri Botanical Gardens curator Peter Raven as a young man, it is now reduced to a single plant near the World War II memorial in the Presidio. Cuttings from the mother plant have been grown and outplanted in the area. A Fish and Wildlife Service Recovery Plan came out in 2002, calling for more cuttings planted in the Presidio and other natural areas of the San Francisco peninsula.

Endangered Grassland Plants

The endangered Presidio Clarkia occurs in serpentine soils created from California’s state rock Serpentinite. Serpentenite occurs in fault zones and tends to have high levels of heavy metals such as zinc and magnesium and low levels of nutrients. Most of the Presidio’s grasslands have been developed or overrun by invasive European grasses. There is an additional population in the Oakland Hills.

The endangered White-rayed pentachaeta is a small annual plant with yellow disk flowers surrounded by white to purple ray flowers. This member of the sunflower family (Asteraceae) is currently known from a serpentine bunchgrass community and native prairie in two small areas of San Mateo County, both on San Francisco Water District lands. It was formerly known from Marin to Santa Cruz counties.

The endangered Fountain thistle is an herbaceous perennial with several stout, erect, reddish stems and large white to pinkish, nodding flowering heads. This member of the sunflower family occurs only in the extremely restricted serpentine seeps of the Crystal Springs region, San Mateo County. It sometimes grows with other rare plants like fragrant fritillary (Fritillaria liliaeca) and San Francisco wallflower (Erysimum franciscanum). The few existing fountain thistle occurrences are on public land owned and managed by CALTRANS and SFWD. An occurrence previously known from Edgewood County Park is thought to be extirpated; no plants have been seen there since one plant was observed in 1993. Construction of Interstate 280 contributed to the decline of fountain thistle by destroying habitat and altering the drainage patterns feeding the seeps in its serpentine grassland plant community; subsequent invasion of pampas grass into several of the colonies further threatens the species.

The threatened Marin dwarf-flax is a delicate annual plant in the flax family, with congested clusters of small rose to whitish flowers. It is found on serpentine ridges covered with bunchgrass from Marin County to San Mateo County and in a serpentine chaparral association in Marin County. There are now 20 known existing occurrences, ranging from land owned by the Marin Municipal Water District to the Presidio of San Francisco to Edgewood Park in San Mateo County to land owned by the San Francisco Water District. Residential development and road and freeway construction have eliminated five of the historically known populations.  of Marin western flax.

The endangered San Mateo thorn mint is an aromatic annual herb of the mint family. The small plants have white flowers, sometimes tinged with lavender, in tight clusters. It is restricted to serpentine soils of grasslands in San Mateo County. The species occupies slopes and flats with deep clay areas. The only remaining remnant population is in Edgewood County Park, and there is an introduced population at Pulgas Ridge. The extant populations are threatened by development and off-road vehicles.