California Rose

California Rose © KKorbholz

California Wild Rose
Rosa californica
NATIVE

Description (Jepson, PlantID.net)

  • Eudicotyledon
    • Eudicots are a major lineage of flowering plants; see family for general characteristics
  • Rose Family (Rosaceae)
  • Semi-deciduous, thicket-forming shrub
  • Stem with thick-based, flat, usually curved prickles (extensions of the epidermis), ≤ 0.6 in. long
  • Leaves
    • Compound (divided into leaflets)
      • 5-7 leaflets with toothed edges
    • Leaflets and axis (supporting structure) sometimes hairy and sometimes glandular (sticky)
  • Flowers
    • Inflorescence (flower arrangement) is a cyme (branched stem with flowers opening from the top down) of 3-30 fragrant flowers
    • Pink, open-faced, 5-petaled flower
      • Numerous stamens (male flower parts) and pistils (female flower parts)
      • 5 sepals (usually green, outer flower parts), sometimes glandular
      • Hypanthium (floral cup, formed from the fusion of petals, sepals, and stamens) is present
    • Ovary superior (above the attachment of other flower parts)
  • Fruit is an aggregate of many achenes (single-seeded, dry fruits that do not split open)
    • Red-orange, fleshy, egg-shaped floral cup (hypanthium), called a hip, encloses the seeds
    • Sepals generally erect and persistent in fruit
  • Height to 8ft.
Prickles © KKorbholz

Distribution

  • Native to California
    • Generally grows in moist areas of woodlands and grasslands
    • See Calflora for statewide observations of this plant
  • Outside California, grows from southern Oregon to northern Baja California, Mexico
  • Grows at elevations to 5,900 ft.

Uses (San Mateo County Parks prohibits removal of any natural material)

  • Wildlife
    • Dense, thicket-like growth provides protection and nesting habitat for birds and mammals
    • Plant structure and material are used by native bees for nesting
      • Some cavity-nesting bees nest in small hollow stems (Jordan 2020)
      • Leafcutter bees (Megachilidae) collect leaf material for nests – look for the half-moon cuts!
    • Pollen source for native bees and other insects
    • Larval food source (host) for larvae of butterflies, moths, and specialist bees (Jordan 2020)
    • Rose hips persist, providing food through the winter for birds and mammals
  • Native people (for Rosa species)
    • Medicinal uses
      • Infusion of petals or buds used as an eye wash and to treat fevers in infants
      • Infusion of leaves used for intestinal ailments
      • Decoction of rose hips used to treat fever, colds, indigestion, rheumatism, and kidney ailments
    • Rose hips, a source of vitamin C and antioxidants, were eaten
    • Blossoms used to make a beverage
    • Stems used in basketry
  • Rose hips are commonly used around the world to make essential oils, teas, jellies, jams, and wines

Name Derivation

  • Rosa (RO-za) – from the Latin for “rose,” probably from the Greek rhodon, “rose”

Notes

  • Wild roses (Rosa species), nightshades (Solanum species), and California poppies (Eschscholzia species) are examples of plants with nectarless flowers that offer only pollen
    • Pollen provides no immediate energy, so bees foraging on these flowers must intermittently visit nectar-bearing plants to keep their sugar buzz (Thorp 2002)
  • Simple petal arrangement is characteristic of wild rose species
    • Most garden roses are double-flowered, meaning some stamens and pistils have been converted to petals
  • California rose is deep rooted and spreads by underground runners, enabling it to survive drought and winter die-back
  • Only native rose in California with strongly curved, thick-based prickles (Ertter 2001)
    • Roses have prickles, rather than thorns or spines, which help deter herbivory
      • Prickles grow from the outer layers (epidermis) of plant stems, as on blackberries
      • True thorns are sharp-pointed modified stems, as on citrus trees and at Edgewood on chaparral pea (Pickeringia montana var. montana)
      • Spines are sharp-pointed modified leaves, as on cacti and at Edgewood on gooseberries, or leaf parts, as on leather oaks
  • Many species of cynipid wasps can co-opt the DNA of Rosa species to create a unique home and food for their larvae in the form of a gall (Russo 2021)
    • Frequently seen with the gall caused by the spiny leaf gall wasp (Diplolepis polita)
  • For an interesting discussion of the complex classification history of the Rosa genus, see Barbara Ertter’s Historical Background essay on the California rose (Rosa californica), where she writes, 
    • “The reason for the tremendous uncertainty in the number of species of Rosa is largely because the genus refuses to resolve itself into a tidy set of unequivocal species, under any species concept.” (Ertter 2001)
Hips of Ground Rose (L), Wood Rose (M), California Rose (R) © DSchiel (L,M), SBernhard (R)

ID Tips

  • May be confused with the 2 other Rosa species at Edgewood — wood rose (R. gymnocarpa) and ground rose (R. spithamea)
Ground RoseWood RoseCalifornia Rose
Growth Habitlow growing, spreadingspreadingtall, thicket-forming
Height≤ 1.6 ft.≤ 3 ft.≤ 8 ft.
Pricklesusually slender, straight or curved

≤ 0.3 in. long
fine, straight

≤ 0.3 in. long
thick-based, flat, usually curved 

≤ 0.6 in. long
Inflorescence≤ 10 flowers≤ 5 flowers≤ 30 flowers
Sepalspersist in fruitdo not persist in fruit persist in fruit
Hips (fruit)glandular (sticky)not glandular (sticky)not glandular (sticky)
Best TrailsLive OakLower Sylvan

At Edgewood

  • Found in woodlands
  • Flowers April – October
  • Fruit persists in winter

See General References

Specific References

Breckling, B. 2008. Spring Wildflowers of Henry W. Coe State Park and the Inland San Francisco Bay Area. Pine Ridge Association.

Ertter, B. 2001. Rosa californica. Native California Roses.

Golden Gate National Park Conservancy. 2021. California Wild Rose.

Jordan, S.F., J. Hopwood, and S. Morris. 2020. Nesting and Overwintering Habitat for Pollinators and Other Beneficial Insects. Xerces Society.

Lady Bird Johnson Wildflower Center. 2018. Rosa californica. Plant Database. University of Texas at Austin.

Prigge, B.A. and A.C. Gibson. 2013. Rosa californica. A Naturalist’s Flora of the Santa Monica Mountains and Simi Hills, California. Web version, hosted at Wildflowers of the Santa Monica Mountains National Recreation Area. United States Department of Interior, National Park Service.

Russo, R. 2021. Plant Galls of the Western United States. Princeton University Press, Princeton, New Jersey.

Simpson, M.G. 2019. Plant Systematics (3rd ed.). Elsevier.

Thorp. R., P. Schroeder, and C. Ferguson. 2002. Bumble bees: Boisterous pollinators of native California flowers. Fremontia 30(3-4): 26-31.

Tree of Life Nursery. 2016. California wild rose – Rosa californica. Blog. California Native Plants, Garden Planning Tools. Tree of Life Nursery.

Wheeler, J. 2017, Mar. 17. 5 ways to increase nesting habitat for native bees. Xerxes Blog. Xerces Society.

Xerces Society. Recommended Plants for Pollinators & Beneficial Insects, California Central Coast Region.