Hydrilla verticillata (Hydrilla) is a perennial aquatic plant (family Hydrocharitaceae). It has been observed in the Mojave and Colorado deserts, south and central coasts, San Francisco Bay Area, and Central Valley. Currently, isolated infestations of Hydrilla are found in Shasta, Yuba, Lake, Calaveras, Madera, Mariposa, and Imperial counties. Hydrilla forms large mats that fill the […]

Centaurea virgata ssp. squarrosa (squarrose knapweed) is a perennial (family Asteraceae) found in the Klamath and Cascade Ranges, Modoc Plateau and northern Sierra Nevada Mountains of California. Squarrose knapweed favors disturbed open sites, including degraded rangeland, logged areas, grasslands and roadsides. Squarrose knapweed seed dispersal is enhanced by soil and water movement, and by clinging […]

Alhagi maurorum (=A. pseudalhagi)(camelthorn) is an herbaceous perennial or shrub (family Fabaceae) found in the central valley, southeastern Sierra Nevada and portions of the Mojave and Sonoran Deserts of California. It favors arid agricultural areas, grasslands, meadows and desert riparian areas. One camelthorn plant can spread rapidly (about 10 m per year in all directions) […]

Arctotheca prostrata (sterile capeweed) is a rosette-forming plant (family Asteraceae) found in coastal prairies and as an urban escape in the San Francisco Bay area and California’s north, central and southern coast. The infertile type of capeweed is cultivated for use as an ornamental groundcover, and a fertile type has also been introduced. The infertile […]

Arctotheca calendula (fertile capeweed) is a rosette-forming plant (family Asteraceae) found in coastal prairies of the San Francisco Bay area and California’s north coast. An infertile type of capeweed is cultivated for use as an ornamental groundcover, and a fertile type has also been introduced. The infertile type is very competitive and can escape cultivation locally […]

Bromus madritensis ssp. rubens (=B. rubens) (red brome) is a cool-season annual grass (family Poaceae) found throughout California, especially in the southern part of the state. Red brome invades disturbed areas, roadsides, agricultural fields, rangelands, and forestry sites, in addition to native communities. Red brome is spreading rapidly in desert shrublands, pinyon pine-juniper communities, three-needle pine woodlands, and […]

Centaurea jacea ssp. pratensis (=Centaurea debeauxii or C. jacea x C. nigra or C. x pratensis) (meadow knapweed) is a bushy perennial (family Asteraceae) found in a small number of disturbed areas in Siskiyou, Del Norte, and Humboldt Counties in northwestern California. Meadow knapweed reproduces by seed and via shoots from the parent plant, and is known […]

Fallopia japonica (=Polygonum cuspidatum) (Japanese knotweed) is a perennial forb/herb (family Polygonaceae ). Plants grow vigorously and create dense colonies that exclude other vegetation. Established colonies are extremely difficult to eradicate. It inhabits disturbed moist sites, roadsides, riparian and wetland areas. Plants typically grow in open, sunny areas on moist soils in cool temperate climates. […]

Festuca perennis (Italian ryegrass) is an annual or biennial grass (family Poaceae) found throughout California except in the Great Basin and deserts. Plants can be distinguished from other several other common grasses by having an unbranched inflorescence with florets and seed that have no awns. Spikelets are arranged in an alternating pattern on stem and […]

Hedera helix (English ivy) is a perennial evergreen woody vine (family Araliaceae). It is found throughout California along the coast, as well as in Shasta and Butte Counties. English ivy grows vigorously in forests where nothing else seems able to compete and inhibits regeneration of understory plants, including forest wildflowers and new trees and shrubs. […]