Leaves odd foliate (most often 5-7 leaflets make up the leaf) Leaflets ovate (egg-shaped), simply or doubly serrate (toothed or having small teeth on the margins of the main teeth, pointing toward the leaflet tips), ~1-3.5 cm long (the outermost, single leaflet usually a little larger than the others), ~1-1.5 cm wide. Petioles (leaf stalks) and rachis (central stem inside the leaf, to which the leaflets attach) are pubescent (hairy/fuzzy) and often prickly. Petioles ~1.5-2.5 cm long, with a pair of irregular stipules winging the base of the petiole. Leaflets are thin but somewhat sclerophyllous (leathery), puberulent (faintly fuzzy), and dark green on top and lighter, pubescent, and sometimes glandular/faintly sticky below. The plant is winter deciduous, though some leaves can persist throughout the year. Stems are famously thorny, this species' thorns being short, flattened at the base, and recurved. Flowers have 5 ovate(egg-shaped, wider toward base) to obovate (egg-shaped, wider toward tip) petals ~1-2.5 cm long, concave upward, pleasantly aromatic, pink or rosy-pink or lavender-pink., sometimes shading to white in the center There are 5 lanceolate (much longer than wide, wider toward the base) sepals with attenuated, tapering, sharp tips to their lobes, and these are dark green and sometimes glandular/sticky. There are many stamens with small yellow anthers (pollen-bearing structures) ringing the center of the corolla and surrounding the numerous and tightly clustered pistils. The flowers are usually carried in clusters (cymes) with anywhere from 1-20 blooms per cluster, each on pedicels (small stems) ~0.5-2 cm long. Blooms May through August. Fruit is a round to ovate "hip" about 0.8-2 cm in diameter. Plant itself is a densely branched and thicket-forming shrub ~0.75-3 m tall and wide. Favors fairly moist places, such as can be found in canyons and along streams and washes. Found below 1600 m throughout most of California and southern Oregon from the foothills of the Sierra Nevada and Cascades west to the coast, in the Transverse and Peninsular ranges into northern Baja.
Rosa californica aka R. aldersonii (Rosaceae): California wild rose or California rose
The development of this key was partially funded through the Geoscience Diversity Enhancement Program (Award #0703798) and through a course of re-assigned time provided by the CSULB Scholarly and Creative Activities Committee. Thanks also to the students in sections of biogeography, introductory physical geography, GDEP, and LSAMP for "test-driving" various editions of this key.