San Francisco


San Mateo


Contra Costa

Case studies and initial discovery links:

Case Study 1:



Affected Community:

Spartina alterniflora: California Invasive Plant Council: High

Introductions to San Francisco Bay and Padilla Bay, Washington, were associated with salt marsh restoration and erosion control projects (Spicher and Josselyn 1985, Daehler and Strong 1996 and 1997a). The introduction in Willapa Bay, Washington, appears to have been in association with oyster shipments during the nineteenth century (Sayce 1988).

Case Study 2:



Affected Community:

Lolium multiflorum: Cal-IPC: Moderate

Case Study 3:



Affected Communities:

Carpobrotus edulis: Cal-IPC: High

Case Study 4:



Affected Communities:


Shapefile of distribution, for certain surveyed areas (not complete picture of SF Bay Area):

Surveyed areas, for above:

calflora: lots of records. not sure how to download/export:

whippet: 2 records

eddmaps: 177 records:

inaturalist: 42 records in CA

blooms May, June, July

The California Invasive Plant Council classifies its potential impact on native ecosystems as High.



The first published record of perennial pepperweed in California is from 1936, when it was collected on a ranch north of Oakdale in Stanislaus County (Bellue 1936). Robbins et al. (1951) state that it may have been introduced to California as a contaminant of sugar beet seed, although no evidence is presented to support this. Recent localized infestations along State Highway 50 may have been initiated from seed or plant fragments that were contaminants in rice straw bales, since these infestations are found in areas of recent construction where straw bales were used for erosion control (Howald pers. observation).

Case Study 5

Hoary Cress (Cardaria draba)

Lens-podded Hoary Cress (Cardaria chalepensis)

IPC moderate

Case Study 6

Tocalote (Centaurea melitensis)

IPC moderate

Case Study 7

Cheatgrass (Bromus tectorum)

most widely distributed invasive plant in US

IPC : high

cheatgrass also interferes with seedling establishment of shrubs such as antelope bitterbrush (Purshia tridentata) and with pine (Pinus sp.) transplants.

Cheatgrass changes the frequency, extent, and timing of wildfires. The early-maturing fine-textured herbage of cheatgrass increases the chance of ignition and the rate of spread of wildfires. Repeated wildfires lead to the loss of native shrubs and continued cheatgrass dominance (Young and Evans 1978, Young et al. 1987). Slow-moving fauna such as desert tortoises also are sometimes killed in the rapidly moving fires (Lovich, pers. comm.).

General invasive species and fire article:

Case Study 8

Gorse (Ulex europaea)

IPC: high

nitrogren fixer

increases fire risk

Data Resources:


Information on wild California plants, georeferenced

Berkeley Ecoinformatics Engine:

API documentation:

WHIPPET (Weed Heuristics: Invasive Population Prioritization for Eradication Tool):

EDDMapS (Early Detection & Distribution Mapping System):

state and county distribution maps for plants, insects, diseases, wildlife


WeedRIC (Weed Research & Information Center):

California weed info



GBIF (Global Biodiversity Information Facility):

“Free and Open Access to Biodiversity Data”

Perennial Pepperweed Surveyed Areas - San Francisco Estuary:

shapefile of surveyed areas, 2004-2007

General invasive plants of Western Forests:

San Francisco Weed Management Area (SFWMA)

Active and Dynamic List of PRIORITY INVASIVE WEEDS for San Francisco County: