Saccharum ravennae (ravennagrass) is a large perennial grass (family Poaceae) found in the Sonoran Desert and Sacramento Valley of California. It is also found in a number of other states throughout the country. Ravennagrass is sold in the nursery trade as a hardier alternative to pampas grass, since it can grow in cooler climates. Ravennagrass […]

Salsola soda (oppositeleaf Russian thistle, glasswort) is an annual (family Chenopodiaceae) found in the San Francisco Bay region. Oppositeleaf Russian thistle is native to southern Europe and inhabits vernal pools, swamps, mudflats and salt marshes. It may form dense stands in estuaries, especially in disturbed areas or places where dredge soil is discharged. It is […]

Salvinia molesta (giant Salvinia) is a floating aquatic fern (family Salviniaceae) found in the lower Colorado River and its drainages in the Sonoran Desert, and in San Luis Obispo County, California. Giant Salvinia was originally introduced for use in aquaria and ponds. It is native to Brazil. It grows in dense mats that may completely […]

Saponaria officinalis (bouncing-bet) is a perennial (family Caryophyllaceae)  that is native to Europe and Siberia. It has escaped gardens where it has been grown as an ornamental and medicinal plant and is now broadly naturalized across the continental United State. In California it is especially problematic near Mono Lake. Bouncing-bet can be distinguished by its […]

Schinus molle (Peruvian peppertree) is an aromatic, evergreen shrub or tree (family Anacardiaceae) found in central and southern California. It is native to more arid parts of the Andes and elsewhere in south America and has been widely introduced as a street tree elsewhere around the world. Like its close relative, Brazilian peppertree (S. terebinthifolius), […]

Schinus terebinthifolia (Brazilian peppertree) is an evergreen shrub or tree found along portions of the southern coast of California. Brazilian peppertree prefers riparian areas, canyons, fields and roadsides where some water is available throughout the year. Its pink fruits are sold as peppercorns, but they may be toxic to humans and animals if too many are […]

Schismus arabicus (Mediterranean grass) is an annual grass (family Poaceae) found mostly in disturbed areas and deserts. It is difficult to distinguish from its close relative Schismus barbatus. Both species contribute to the conversion of desert shrubland into annual grassland by carrying fire across open areas, where they ignite and kill native shrubs.

Senecio jacobaea (tansy ragwort) is a noxious perennial, biennial, or sometimes annual weed (family Asteraceae) native to northern Africa, Asia, and Europe, that that occurs mostly in northern California. Plants are ruffled rosettes when young and erect when mature, growing up to  4′ . Leaves are twice pinnately compound and dark green. Flower heads have […]

Sesbania punicea (red Sesbania, scarlet Wisteria) is a deciduous shrub or small tree (family Fabaceae), up to 4 meters tall. Sesbania punicea is mostly found in riparian areas in the Central Valley, forming clusters so thick that access to the river becomes difficult to impossible. It displaces native plants used by wildlife and contributes to […]

Silybum marianum (blessed milk thistle) is a winter annual or biennial with prickly leaves (family Asteraceae). It is widely spread throughout California in overgrazed pastures and along fencelines and other disturbed areas. Blessed milk thistle produces tall, dense stands that outcompete native species.