Abstract
Desert peach (Prunus andersonii A. Gray [Rosaceae]) is a common component of sagebrush and desert mountain shrub communities in the Great Basin and Mojave Desert. Freshly harvested seeds of this species readily germinate without pre-treatment if seeds remain moist immediately after cleaning. Unlike many Prunus L. species, stored desert peach seeds require only a 6 to 8 wk naked, cold stratification to obtain high rates of germination. Stored seeds remain viable for at least 6 y. Seedlings can be produced in 7 mo in 164 ml (10 in3) Ray Leach cells. This species is utilized for desert mountain shrub and sage steppe restoration and is suitable for xeric landscapes of the Great Basin and desert regions of Nevada and California.

Desert peach blooming in early spring.
The Nevada Division of Forestry nursery program began in 1957 and currently consists of 2 container nurseries, Washoe State Nursery (WSN) near Carson City, Nevada, and Las Vegas State Nursery in Las Vegas, Nevada. WSN produces tree, shrub, forb, grass, and wetland species for conservation uses in the Sierra Nevada and Intermountain West. Seedlings are typically started in 164 ml (10 in3) cone-tainers (Ray Leach Cone-tainers, Stuewe & Sons Inc, Tangent, Oregon), and WSN has greenhouse capacity for 125,000 containers of this size. Staff consists of a nursery manager, a conservation aid, and a conservation camp inmate crew that varies in size seasonally depending on workload. WSN has grown desert peach for at least 15 y.
Desert peach is a thorny, multi-stemmed, early flowering shrub 1 to 3.5 m (3–7 ft) tall that is common in the Great Basin of Nevada. It ranges south along the eastern slopes of the Sierra Nevada of California to the Desert Mountain Ranges of the northern Mojave Desert, California. Mature shrubs produce hundreds of showy, bright pink to occasionally white flowers per stem (see photo on opening page). Once established, individual stems naturally layer and produce adventitious roots where stems are buried by blowing sand or accumulated soil.
This drought-adapted species is found growing in sands, sandy loams, and rocky or gravelly soils in washes, canyons, and rocky slopes in pinyon-juniper, sage-scrub, and on sparsely vegetated slopes. It is common on poorly developed granitic soils. In Nevada and California, desert peach is a frequent component of antelope bitterbrush (Purshia tridentata (Pursh) DC. [Rosaceae]), curl-leaf mountain mahogany (Cercocarpus ledifolius Nutt. [Rosaceae]), and big sagebrush (Artemisia tridentata Nutt. [Asteraceae]) community types, on slopes and flats with well-drained, rapidly permeable soils. This species provides important browse for mule deer, cover for birds and small mammals, and is important for early emerging or migrating native pollinators in the Great Basin and Mojave Desert. Desert peach readily re-sprouts from subterranean adventitious buds and lignotubers following fires. It is frequently one of the most common re-sprouting shrubs in post-fire sagebrush communities that have been infested with cheatgrass (Bromus tectorum L. [Poaceae]) (Gucker 2007) and is important for post-fire soil stabilization on steep desert mountain slopes.

Desert peach with thorny stems and ripe fruit.
Desert peach begins flowering from March to May in northern Nevada, though the flowering period usually lasts only a few weeks. Fruits typically ripen from June to August. Mature fruits are puberulent, yellowish to reddish-orange with soft, tender flesh, or leathery, dry flesh depending on moisture availability during development. Fruit skins usually split open at maturity. Thick endocarps enclosing the seeds are tan to brown, somewhat rounded to elliptic and flattened, and 1.0 to 1.5 cm (0.4–0.6 in) long. On average, desert peach has approximately 4200 seeds/kg (1900 seeds/lb).
SEED PROPAGATION
Seed Collection Information
Seeds are hand-collected at several sites in the local area where it is found in dense stands between mature big sagebrush and antelope bitterbrush. Fruits must be monitored often when near-ripe, because rodents will strip plants seemingly overnight once fully mature. Fruits are kept in woven polypropylene seed bags in a walk-in cooler at 1.7 °C (35 °F) prior to cleaning.
Fruits are mixed with water in buckets and allowed to open-ferment at room temperature for up to 5 d to soften flesh. Fruits are then processed with a Dybvig macerator (Dybvig Seed Cleaner, Bob Mills, Astoria, Oregon) using a wet process to separate flesh from seeds. The resulting seed and flesh mixture is put into a bucket, and debris and unfilled seeds are floated off with a slow stream of water. This method results in high purity seed, though some insect-damaged seeds will remain.
Seeds are air-dried on wire mesh racks for 10 to 14 d depending on temperature, then stored in woven polypropylene seed bags in a walk-in cooler at 1.7 °C (35 °F) and ambient humidity. Seeds can retain good viability for up to 6 y under these conditions. We store seeds for 5 mo from harvest and cleaning to pre-treatment in early winter.

Desert peach fruits showing split skins and seed removed.
Methods Used for Seed Pre-treatment
Freshly harvested seeds will readily germinate if kept moist. In fact, WSN employees used to take freshly harvested fruits, soak them in water until the flesh could be removed, then keep the cleaned seed submerged until the endocarp split, at which time they were planted. With that method, germination rates were approximately 60%. We have no extant records of the resulting plants, however, and this summer sowing technique has been discontinued in favor of spring sowing.
Stored desert peach seeds exhibit a non-deep, physiological dormancy and require cold, moist stratification. The hard endocarp is permeable to water. Unlike many other Prunus L. species, desert peach seeds do not require scarification or mechanical removal of the endocarp or a prolonged after-ripening for full embryo development prior to stratification.
We place seeds in mesh paint strainer bags for a 48 h running water rinse, then soak them in a 5% household bleach solution for 15 min before placing seeds into a naked (no media), cold, moist stratification. Hydrated seeds are placed in a shallow layer in plastic storage containers under refrigeration at 1.7 °C (35 °F) for approximately 8 wk. Seeds are tumbled weekly to prevent mold formation. After 6 wk, we check seeds weekly for germination. Nevada seed sources germinate as early as 55 d after cold, moist stratification and continue to germinate over a several week period. Our germination percentages can be as high as 88%.
We plant germinants, just as the endocarp splits and the radicle emerges, into 164 ml (10 in3) Ray Leach cell containers filled with a pre-moistened growing medium of 1:1:1:1 composted bark, peat, vermiculite, and perlite (v:v:v:v). Pumice or cinder can also be used as a medium component for this species, since it prefers rapid drainage and good aeration, particularly if transplanted to larger containers. Irrigation practices are adjusted to allow the medium to dry well between irrigations because plants are susceptible to overwatering during germination and growth. We have also found desert peach susceptible to Fusarium root rot and now add Root Shield Plus granules to all our media at 1.2 kg/m3 (2 lb/yd3).
Seedlings are germinated in a greenhouse at a 27 °C day/13 °C night (80 °F/55 °F) temperature cycle. During germination, seeds are kept evenly moist. Seedlings grow quickly and are usually well established with true leaves approximately 4 wk after sowing. We have occasionally seen mutations in seedlings, such as red-purple leaves or narrow, linear leaves, which could be developed into interesting cultivars.
During active growth, we fertilize seedlings with a custom formulation of 200-50-150 ppm NPK and micronutrients every other week. Seedlings are grown in the greenhouse to provide optimum temperatures and to manage irrigation.
Seedlings are hardened in midsummer by reducing irrigation and fertilization and by moving seedlings to the outdoor growing facility where more air circulation and full direct sunlight appear to be beneficial. During the hardening phase, seedlings are fertilized with a custom formulation of 50-50-70 ppm NPK and micronutrients every other week. Irrigation is applied only when medium is dry. Seedlings are hardened outdoors for 8 to 16 wk prior to winter storage or outplanting.
Seedlings not planted by November are overwintered at the nursery in the outdoor lath house or unheated greenhouse, depending on expected winter precipitation. Care must be given to ensure that root systems remain relatively dry during dormancy and overwinter storage. Typically, seedlings are ready for outplanting during September and October, or the following April. Desert peach is a beautiful, tough, native shrub that deserves more consideration in both restoration and xeric landscapes.
Footnotes
Photos by Ryan Sharrer
This article was prepared by a U.S. government employee as part of the employee’s official duties and is in the public domain in the United States.