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Alnus (rhombifolia)

Lee Riley
USDA FS - Dorena Genetic Resource Center
34963 Shoreview Road
Cottage Grove, Oregon 97424
541-767-5709 (fax)

Family Scientific Name: Betulaceae
Family Common Name: Birch
Scientific Name: Alnus rhombifolia
Common Name: White Alder, California Alder, Sierra Alder
Species Code: ALRH2
Ecotype: John Day area, Oregon
General Distribution: Moist soils or on the edge of permanently wet areas, like stream banks. Grows in part shade and in full sun. It is tolerant of sand and clay. Is native to and persists in western North America, from western Montana and south to San Diego county in California.
Propagation Goal: Plants
Propagation Method: Seed
ProductType: Container (plug)
Stock Type: 444 ml (27 in3) container
Time To Grow: 18 weeks
Target Specifications: Stock Type: Container seedling Root System: Firm plug in container.
Propagule Collection: Female catkins mature in fall though the seeds disperse in winter. Notably, the old, woody blackish catkins from the previous year can also sometime still be found.
Pre-Planting Treatments: Seeds are placed in fine mesh bags into a 1% hydrogen peroxide (3:1 water/3% hydrogen peroxide) soak for 24 hours, rinsed, and placed in water for an additional 24 hours.
Seeds are sown into trays filled with stabilized medium plugs (Q-plugs). Trays are sealed inside plastic bags and placed into refrigeration at 1 to 3 °C for 20 days. Trays are checked weekly and kept moist throughout the stratification period. If mold is evident, trays should be treated with 1% hydrogen peroxide.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Greenhouse growing facility.
Q-plugs are lightly covered with nursery grit. Seedlings are transplanted to target containers approximately 3 weeks following removal from stratification.
Growing medium used is 40:20:20:20 peat:composted fir bark:perlite:pumice with Apex controlled release fertilizer (16N:5P2O5:10K2O with minors; 6- to 7-month release rate at 21°C) at the rate of 2 g Apex per 444 ml container.

Establishment Phase: Germination is fairly uniform and is usually complete in 2 weeks. Following germination (while still in Q-plugs), plants are fertilized with soluble 12-2-14-6Ca-3Mg at 75 to 100 ppm for 2 weeks.
Length of Establishment Phase: 2 to 3 weeks
Active Growth Phase: Plants grow rapidly following establishment. Soluble fertilizer (20-9-20 NPK, 20-18-18 NPK, or 17-5-24 NPK) at 100 to 150 ppm is applied weekly throughout the growing season.

Length of Active Growth Phase: 15 weeks
Hardening Phase: No dry-down is done to induce dormancy. Seedlings are moved to an outdoor growing area in early September.
Length of Hardening Phase: 2 to 3 weeks
Harvesting, Storage and Shipping: Harvest Date: Mid to late October
Storage Conditions: Seedlings are usually outplanted in fall. No storage except in outdoor growing area. Plants are well irrigated prior to shipping and shipped in containers.
Other Comments: USDA plant hardiness zones 8 to 11
Wetland classification: FACW
Has been seen to hybridize with Thinleaf alder (Alnus incana) in southwestern Idaho.
Main pest is the flatheaded borer in California as well as tent caterpillars.
References: Calflora. n.d. Taxon report 252, Alnus rhombifolia Nutt. white alder. URL: https://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=252 (accessed 21 Oct 2019).

Calscape. nd. White alder Alnus rhombifolia .. California Native Plant Society. URL:
https://calscape.org/Alnus-rhombifolia-(White-Alder) (accessed 21 Oct 2019).

Gilman EF, Watson DG. 1993. Alnus rhombifolia white alder. USDA Forest Service. Fact Sheet ST-72 URL: http://hort.ufl.edu/database/documents/pdf/tree_fact_sheets/alnrhoa.pdf (accessed 21 Oct 2019).

Sawyer JO Jr. n.d. Alnus rhombifolia white alder. Berkeley (CA): University of California, The Jepson Online Interchange California Floristics. URL: URL: http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12722 (accessed 21 Oct 2019).

USDA Natural Resources Conservation Service. Alnus rhombifolia Nutt. white alder. URL: https://plants.usda.gov/core/profile?symbol=ALRH2 (accessed 21 Oct 2019).


Riley, Lee E.; Kamakura, Renata. 2020. Propagation protocol for production of Container (plug) Alnus rhombifolia Plants 444 ml (27 in3) container; USDA FS - Dorena Genetic Resource Center Cottage Grove, Oregon. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2020/09/18). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.

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