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Picea (engelmannii)

Kasten Dumroese
Research Plant Physiologist
USDA Forest Service, Southern Research Station
1221 S. Main St.
Moscow, Idaho 83843
(208) 883-2324

Family Scientific Name: Pinaceae
Family Common Name: Pine Family
Scientific Name: Picea engelmannii Parry ex. Engelm.
Common Name: Engelmann spruce
Species Code: PICENG
Ecotype: Northern Idaho
General Distribution: Engelmann spruce ranges from British Columbia and Alberta to Arizona, New Mexico and northern Mexico. In Idaho, it reaches it maximum size on deep, rich, loamy soils of high moisture content.
Propagation Goal: plants
Propagation Method: seed
ProductType: Container (plug)
Stock Type: 66 ml (4 cu. in) Ray Leach "Cone-tainers"
Time To Grow: 8 Months
Target Specifications: Height = 15 to 20 cm Root-collar diameter = 2.5 to 2.8 mm Firm root plug >2% foliar N
Propagule Collection: Ovulate cones are solitary at the tips of branches in the upper portion of the tree crown. Mature seed cones are pale brown and 2.5 to 8 cm (0.16-0.98 in) long. Each cone contains numerous, elliptical, dark grey winged seeds that are 2.5 mm (0.09 in) long. Seeds are wind dispersed. Trees begin bearing cones at 20 years and produce good seed crops every 2 to 13 years.
Propagule Processing: Cones can be collected from recently felled trees or by using a pole pruner on medium-sized trees. Spruce seeds require careful handling after harvest and during extraction. Cones can air-dry in half filled burlap sacks or on open screens for a few weeks or outside if ventilation is good.
Large nurseries use kilns set at 38 to 49øC (100 to 120øF) to open cones within 24 hours. After drying, tumbling or shaking releases seeds from scales. Small seedlots are easily de-winged by rubbing seeds inside a moistened cotton bag. Larger seedlots are cleaned by a fanning mill or air screen cleaner. Empty seeds are removed by air and gravity separation.
Seeds/kg = 300,000 to 496,760 (150,000 to 225,800 seeds/lb).
Seeds dried to 7% seed moisture content remain viable for 7 years when stored at temperatures of -18 to 3ø C (0 to 37øF).
Pre-Planting Treatments: Seeds are placed into fine mesh bags and soaked in running tap water for 48 hours to ensure imbibition.
Mesh bags are placed into plastic bags and seeds are stratified (cold, moist) for 28 days at 1 to 2øC (34 to 36øF). After stratification, seeds are soaked 24 hours in running tap water.
Based on cumulative germination at 21 days in a germination test, the total amount of seeds needed for the crop is determined to ensure 90% to 95% of the cells have at least one seedling.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Seedlings are grown in 2 fully-controlled greenhouses. Photoperiod is extended by 300 watt incandescent lamps (15 min on/off cycles) at an intensity of 500 lux. Irrigation is applied by an overhead traveling boom system, with nozzles spaced every 40 cm. Fertilizers are injected into irrigation water with a 1:100 injector.
Containers are filled with a 1:1 (v:v) Sphagnum peat moss and vermiculite medium having a pH of 4.2.
Seeds are sown in late March and are immediately covered with a shallow layer of white grit or Forestry sand (6 mm deep) and immediately irrigated (acidified to a pH around 6.0) until the medium is saturated. Using a medium with low pH, irrigating with acidified water, using grit to allow air circulation around the root collar, keeping relative humidity low, and using underbench air circulation and heating reduces damping-off disease. Day-time greenhouse temperatures are maintained at 24 to 27øC (75 to 80øF), and night-time temperatures are maintained at 18øC (65øF).
Establishment Phase: Once seedcoats begin to fall off germinating seedlings, seedlings are thinned to 1 seedling per container. Germination is usually complete within 21 to 28 days.
Photoperiod lights remain activated. Nutrients are supplied about twice a week. During the establishment phase (6 to 8 weeks), seedlings are fertilized with Peters Professional Conifer Starter (7N:40P2O5:17K2O; The Scotts Company, Marysville, Ohio) to supply 42 ppm N, along with micronutrients (Fe, B, MgSO4). Phosphoric acid is used to keep pH of irrigation water around 6.0. Seedlings are irrigated when blocks weigh 80% to 85% of saturated weight. At the end of week 6, medium is leached with irrigation water to remove salt build-up. Day greenhouse temperatures are maintained at 24 to 27øC (75 to 80øF) and night temperatures around 18øC (65øF).
Length of Establishment Phase: 6 weeks
Active Growth Phase: During the active growth phase, day-time greenhouse temperatures are maintained at 21 to 24øC (70 to 75øF) and night temperatures are maintained at 18øC (65øF). Photoperiod control is continued.
Nutrients are supplied about twice a week using Peters Professional Conifer Grower (20N:7P2O5:19K2O; The Scotts Company, Marysville, Ohio) alternated with calcium nitrate (15.5:0:0:10) to supply 120 and 92 ppm N, respectively, along with micros (Fe, B, MgSO4).
Containers are irrigated when blocks weigh 80% to 85% of saturated weight, but this is slowly decreased so that by the time growers wish to initiate buds, containers are irrigated at about 70% saturated weight. Seedling heights are compared to those on a target growth curve, and if growth exceeds targets, nitrogen is reduced by decreasing the amount of calcium nitrate. Seedlings generally reach desired heights by week 12, and medium is leached with copious amounts of irrigation water. Medium is then allowed to dry down until it is just barely moist.
Length of Active Growth Phase: 6 weeks
Hardening Phase: Between weeks 12 and 15, when irrigation is necessary, Peters Professional Conifer Finisher (4N:25P2O5:35K2O; The Scotts Company, Marysville, Ohio) is applied every irrigation along with micronutrients (Fe, B, MgSO4) and phosphoric acid. After week 15, finisher is alternated with calcium nitrate at the rate of 92 ppm N. Photoperiodic lighting is discontinued. Temperatures are allowed to go to ambient, but preferably under 27øC (80øF) during the day. However, minimum greenhouse temperature allowed is -2øC (28øF). Seedlings are ready to be packed in January. From mid-September until pack-out, day temperatures are kept cool as possible and we prevent night temperatures from dropping below -2øC (28øF). Seedlings are hardened for 18 to 22 weeks.
Length of Hardening Phase: 18 weeks
Harvesting, Storage and Shipping: Seedlings are extracted for storage in late November through December. Seedlings are well-watered before removal but foliage should be dry before packing.

Seedlings are placed within plastic bags inside waxed boxes or plastic tubs and stored at 0.5øC (33 to 34øF). Seedlings are monitored for storage mold problems. Storage molds can be reduced by packing disease-free stock, storing them for the shortest possible duration, inspecting the crop for on-set of mold, shipping seedlings with minor mold occurrence first, and keeping temperatures below freezing.
Length of Storage: 4 to 5 months
Other Comments: Between crops, containers should be sterilized. We submerge Ray Leach "Cone-tainers" in hot water (75 to 85øC [167 to 185øF]) for 15 to 30 seconds to remove pathogens.
This protocol was originally developed in the mid-1980s when David L. Wenny was Director of the nursery and published as Idaho Forest, Wildlife and Range Experiment Station Bulletin 47.
References: Dumroese RK, James RL, Wenny DL. 2002. Hot water and copper coatings in reused containers decrease inoculum of Fusarium and Cylindrocarpon and increase Douglas-fir seedling growth. HortScience 37:943-947.
Wenny DL, Dumroese RK. 1990. A growing regime for container-grown spruce seedlings. Moscow (ID): University of Idaho, Idaho Forest, Wildlife and Range Experiment Station. Bulletin 47. 8 p.


Dumroese, Kasten. 2009. Propagation protocol for production of Container (plug) Picea engelmannii Parry ex. Engelm. plants 66 ml (4 cu. in) Ray Leach "Cone-tainers"; USDA Forest Service, Southern Research Station Moscow, Idaho. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2021/05/08). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.

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