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Protocol Information

Rae Watson
Forestry Technician
USDA FS - J Herbert Stone Nursery
2606 Old Stage Rd.
Central Point, Oregon 97537

Family Scientific Name: Rosaceae
Scientific Name: Purshia tridentata
Common Name: Bitterbrush
Propagation Goal: Plants
Propagation Method: Seed
Product Type: Bareroot (field grown)
Stock Type: 1+0
Target Specifications: Minimum height of 4 inches and caliper of 3mm.
Propagule Collection: Most seed comes from wild collections, with the remainder coming from seed orchards managed by the Forest Service and Bureau of Land Management. All seed is kept separate by the collection area, elevation and date collected. All seed is collected or contracted for collection by the Forest Service and Bureau of Land Management or other government agencies. All seed is collected in the fall.
Propagule Processing: Seed is sent to Bend Pine Extractory in the fall for cleaning. It is dried to between 5 and 8% moisture and placed in air tight plastic bags, then stored in seed freezers set at -15C (5F) at the nursery. This seed has a long storage life under these conditions.
Pre-Planting Treatments: Seed is placed in mesh bags and soaked in cold running water for 48 hour. The seed is then laid out 3cm (1 in) thick on trays with fine screen meshed bottoms and placed in cold stratification rooms for 30 to 45 days. Rooms are equipped with foggers to keep the naked seed moist at all times (seed covered with free moisture). Temperatures are set at 1C (33F). Seed is monitored daily to detect seed mold. If mold is found, the seed is hosed down with water.
Growing Area Preparation/
Annual Practices for Perennial Crops:

The nursery soils are a sandy loam (Central Point Sandy Loam Soil Series – Coarse-loamy, mixed, mesic Pachic Haploxeroll). Nine months before sowing, in late spring, 2.5cm (1in) inch of fresh sawdust is applied and disked into the surface. During the summer, the fields are irrigated to encourage weeds to sprout. The fields are disked at regular intervals to keep them free of weeds. Soils are formed into 1.2m (4ft) wide raised beds separated by a 0.6m (2ft) tractor path. There are six beds between irrigation pipelines.
Establishment Phase: Seed is sown through a modified Oyjard seed drill. Seed is sown for an initial seedling density of 215 seedlings/m2 (20 seedlings/ft2). Attached to the front of the seed drill is a fertilizer bander. Depending on our soil analysis the bander places 500 kg/ha (450 lb/ac) of potassium sulfate (0-0-53) and 400 kg/ha (360 lb/ac) of ammonium phosphate (11-52-0) is placed at a depth in the soil of10cm (4in). The seed drill has been adapted by attaching 8 steel bands to the drum. The bands are 3cm (1¼ in) wide by 1cm (3/8in) deep and 15cm (6 in) apart. As it rolls in front of the seeder, the band creates a small impression for the seed to drop into. The tubes of the seed drill have been increased in size to allow large seed to pass through and drop directly into the impressions. Behind the seed tubes are small wheels that press the seed into the surface of the soil. Within a half hour of sowing, and then covered with 1cm to 1.3cm (3/8 to ½ in) of fresh (undecomposed) sawdust. The sawdust is sprayed with Agrilock at 15% solution to hold it in place in case of high winds. Then the seedbeds are sprayed with Goal (oxyfluorfen) at 2 pints per acre as a pre-emergent control for weeds.The seedbeds are irrigated when the seed appears to be drying out. This occurs only on warm days. There is no fertilization during this period.
Length of Establishment Phase: 4 weeks
Active Growth Phase: Irrigation: Soil tensiometers are placed at 15cm (6in) depths and monitored at least once per week. Soils are irrigate to 30cm (12in) when tensions are at -0.2 or higher. Light (5 minute) bursts of irrigation are given when surface soil temperatures (temperature probe placed under a ¼ inch of soil) are 33C (91F) in June; 35C (95F) in July; 38C (100F) in early August and 40C (104F) in mid August. Fertilizer: Fertilizer is applied in granular form over the seedlings. After application is complete, the fertilizer is washed off the foliage and into the soil with a half hour of irrigation water. Four applications are made: Approximately 6 weeks after emergence, 56 kg/ha (50 lbs/ac) of ammonium nitrate is applied when lateral roots have developed from new germinants. 8 weeks after emergence – 84 kg/ha (75 lbs/ac of ammonium nitrate. 10 weeks after emergence – 181 kg/ha (162 lbs/ac) ammonium sulfate, 12 weeks after emergence – 120 kg/ha (100 lbs/ac) of ammonium nitrate and 14 weeks after emergence – 120 kg/ha(100 lbs/ac) of ammonium nitrate.IPM: Handweeding of beds if necessary. If lygus insect found to damage buds, utilize mechanical insect control (Bug suck vacuum) and isecticide (Pydrin) at 10 day intervals until damage from insect no longer observed.
Length of Active Growth Phase: 4 months
Hardening Phase: By the third week in August or when the seedlings dormancy is induced.Irrigation: Only irrigate when the surface temperatures exceed 38C (100F) or pre-dawn plant moisture stress (PMS) exceeds 10 bars. In the early fall the soil profile is completely moistened and plants are kept below 5 bars pre-dawn PMS. From October through the early portion of November, the seedlings are protected from frosts through irrigation. Fertilizer: Two applications of 112 kg/ha (100 lbs/ac) applied in mid-fall after bud set 2 weeks apart.IPM: Handweed beds if needed. Prunes and wrenches: No prunes or wrenches.
Length of Hardening Phase: 1 month
Harvesting, Storage and Shipping: Usually all bitterbrush is lifted between December and early February. Seedlings are hand-lifted after the seedlings beds have been undercut using an Lundeby lifter. Lifting conditions must be in unsaturated soils, PMS below 15 bars and temperatures above –3C (27F). Seedlings are stored at 1C (33F) and 100 percent humidity for 1 to 5 days before sorting. Sorting removes seedlings that do not meet target specifications (see above). Many clients ask for seedlings to be rootpruned between 23 and 30cm (9 and 12 inch) for planting reasons. We accomplish this with paper cutters. At clients request, we will place a rubber band around a group of seedlings, usually 25. Seedlings are placed in 3 ply bags and sown shut. The bags are placed on racks and stored in coolers at 1C (33F) for storage durations less than 2 months or in freezers at –1C (29F) for greater than 2 months.
Length of Storage: up to 5 months

Steinfeld, David E. 2001. Propagation protocol for production of field-grown Purshia tridentata plants (1+0); USDA FS - J Herbert Stone Nursery, Central Point, Oregon. In: Native Plant Network. URL: http://www.nativeplantnetwork.org (accessed 31 August 2015). Moscow (ID): University of Idaho, College of Natural Resources, Forest Research Nursery.