Holodiscus dumosus

Mountain Spray (Rockspiraea)

Rosaceae

The Basics

Rockspirea occurs in all stages of succession as long as the canopy is open or only partially closed. It grows on both seral shrubfields and in climax forest habitat types. In successional stages of the rockspirea phase of white fir/Gambel oak habitat types on the Lincoln National Forest, rockspirea and other shrubs dominate for "a few years" after stand-replacement fire. Native Americans of the Great Basin ate the seeds, and pioneers made nails from the wood. The Navajo used a decoction of the leaves to treat influenza. The Tewa ate the fruits...Because they retain heat and snow melts off from them early, conifer/rockspirea scree habitat types of Arizona and New Mexico are important sites for groundwater recharge.

Identification

Rockspirea is a deciduous shrub from 0.5-6.2 m tall. It is generally shorter than creambush oceanspray. Its form is spreading; mature plants may reach 1.5-3 m across. Main branches arise from the root crown. Terminal branches may be weakly spinescent. Bark is shreddy. The roots are dense and spreading. Its roots reach at least 30 cm below ground. The leaves occur mainly on spur branches; they range from 1-2.3 cm long and 0.4-1.2 cm wide. Rockspirea leaves and inflorescences are smaller than those of creambush oceanspray. Its inflorescence is a panicle or a raceme from 5-20 cm long.

Threats

Fire top-kills rockspirea. Rockspirea sprouts from the root crown and establishes from seed after fire...Rockspirea and other sprouting shrubs may facilitate postfire establishment of conifers...The coniferous and hardwood communities in which rockspirea occurs historically experienced mostly frequent, low- to mixed-severity fires. Fire-return intervals tend to lengthen from dry, low-elevation sites to cool, high-elevation sites where rockspirea is most common.Rockspirea is not usually overbrowsed due to its relative unpalatability and habit of growing in often inaccessible places. In riparian areas used as livestock rangelands, it may be ignored at the expense of grasses.

Reproduction

Flowering and Fruiting - Rockspirea flowers are perfect. They are pollinated by insects...Wind disperses rockspirea seeds...Seed viability may be low in rockspirea. One study found seed soundness averaged 7% for rockspirea. Seeds are dormant and probably require overwinter stratification in the field.

Asexual regeneration - Rockspirea sprouts from the root crown. Its sprouting ability is not well documented. Since creambush oceanspray and rockspirea are closely related and sprouting is the primary method of regeneration for creambush oceanspray, sprouting it is likely rockspirea's primary method of regeneration as well.

Species Distribution

Citation

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
Map Photo credit

USFS Plant Database
Fryer, Janet L. 2010. Holodiscus discolor. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/shrub/holdis/all.html [2021, March 29].
Photo credit