A diverse array of plant communities is found on Santa Rosa Island, including coastal strand, coastal bluffs, grasslands, coastal sage scrub, chaparral, woodlands, pine forests, riparian and marsh communities. There are about 500 different native and introduced plants which occur on the island. About 35 of these plants are endemic to the California Channel Islands.

There are four plants restricted to Santa Rosa Island: Live-forever (Dudleya blochmanae insularis), manzanita (Arctostaphylos confertiflora), gilia (Gilia tenuiflora hoffmannii), and a variety of Torrey Pine (Pinus torreyana insularis).

There are stands of Bishop pine (Pinus muricata), Santa Cruz Island pines (Pinus remorata), as well as a stand of Torrey pines. Torrey pines are found on the northeast sector of Santa Rosa Island. They grow at elevations between 200-500 feet. This is the only native stand of Torrey pines on any Channel Island. They occur naturally at only one other location, on the southern California coast just south of Del Mar in San Diego County.