Wood Rose

Dwarf Rose, Baldhip Rose
Rosa gymnocarpa var. gymnocarpa
NATIVE

Description (Jepson, PlantID.net)

• Eudicotyledon
  • Eudicots are a major lineage of flowering plants; see family for general characteristics
• Rose Family (Rosaceae)
• Deciduous shrub, erect to spreading
• Stems are numerous and slender
  • Prickles (extensions of the epidermis) are straight and fine, ≤ 0.3 in. long
• Leaves
  • Compound (divided into leaflets)
    • 5-9 leaflets with toothed edges
• Flowers
  • Inflorescence (flower arrangement) usually solitary, or sometimes a cyme (branched stem with flowers opening from the top down) of 3-5 fragrant flowers
  • Pink to red, 5-petaled, open-faced 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
  • Pedicels (stalk of a single flower) generally and sepals sometimes (usually green, outer flower parts) with stalked glands
  • 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
  • Deciduous sepals drop off the hip earlier than deciduous sepals of other rose species
• Height to 3 ft.

Distribution

• Native to California
  • Generally grows as an understory plant in woodlands, but also found in chaparral and grasslands
  • See Calflora for statewide observations of this plant
• Outside California, grows north to British Columbia and east to Idaho and Montana
• Grows at elevations to 6,000 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 butterflies, moths, and specialist bees (Jordan 2020)
  • Many species of gall (cynipid) wasps 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)
    • Galls are abnormal, tumorlike growths induced by parasites (e.g. insect, mite, or bacterium)
    • Wood roses are frequently seen with the gall caused by the spiny leaf gall wasp (Diplolepis polita)
  • Rose hips persist, providing food through the winter
• 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”
• gymnocarpa (jim-no-KAR-pa) – from the Greek gymnos, “naked,” and karpos, “fruit,” referring to the deciduous sepals, which are dropped especially early in this species

Notes

• Simple petal arrangement is characteristic of wild roses
  • Most garden roses are double-flowered, as some stamens and pistils have been converted to petals
• 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)
• 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
• Host to the fungus-like microorganism Phytophthora ramorum, which causes Sudden Oak Death (SOD)
  • At Edgewood, the two species known to be highly susceptible to SOD are coast live oak (Quercus agrifolia var. agrifolia) and Pacific madrone saplings (Arbutus menziesii)
  • For a complete list of known hosts and host associates see USDA Risk Analysis for Phytophthora ramorum, pp.6-9
• Edgewood’s wood rose is classified as a variety
  • Variety indicates a population with small morphological variations, e.g. color, seen throughout the geographic range of the species; interbreeding is possible
  • Subspecies indicates a geographically-separated population with distinct morphological characteristics; when not isolated, interbreeding is possible
  • In practice, botanists have not consistently applied these ranks
• 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)

ID Tips

• May be confused with two other species of roses at Edgewood, California rose (R. californica) and ground rose (R. spithamea)

	Ground Rose	Wood Rose	California Rose
Growth Habit	low growing, spreading	spreading	tall, thicket-forming
Height	≤ 1.6 ft.	≤ 3 ft.	≤ 8 ft.
Prickles	usually slender, straight or curved … ≤ 0.3 in. long	fine, straight … ≤ 0.3 in. long	thick-based, flat, often curved  … ≤ 0.6 in. long
Inflorescence	≤ 10 flowers	≤ 5 flowers	≤ 30 flowers
Sepals	persist in fruit	do not persist in fruit	persist in fruit
Hips (fruit)	glandular (sticky) … spherical	not glandular (sticky) … ellipsoid to spherical	not glandular (sticky) … (ob)ovoid
Best Trails	Live Oak	lower Sylvan	…

At Edgewood

• Found in woodlands
• See iNaturalist for observations of this plant
• Flowers April – September

Specific References

Breen, P. 2020. Rosa gymnocarpa. Department of Agriculture, College of Agricultural Sciences, Oregon State University.

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

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

Pavik, P.L.S., and D.M. Skinner. 2013. Baldhip rose Rosa gymnocarpa Nutt. Plant Guide. United States Department of Agriculture, Natural Resources Conservation Service, Plant Materials Center, Pullman, Washington.

Reed, W.R. 2020. Rosa gymnocarpa. Fire Effects Information System. United States Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

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

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

General References

Calflora Database. 2014. Berkeley, California.

Calscape. 2018. California Native Plant Society.

Charters, M.L. 2015. California Plant Names: Latin and Greek Meanings and Derivations.

Charters, M.L. 2017. Southern California Wildflowers: Guide to the Pronunciation of Specific, Generic and Family Names.

Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.

Dave’s Garden.

Elpel, T.J. 2013. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, Pony, Montana.

Flora of North America. efloras.org.

Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.

Keator, G. 2009. California Plant Families. University of California Press, Berkeley and Los Angeles, California.

Native American Ethnobotany DB.

Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.