Pinaceae (Pinus)
Pinus (ponderosa)
Pinaceae
Pine Family
Pinus
ponderosa
Variety
ponderosa
Laws.
Ponderosa pine
Northern Rocky Mountains
In northern Idaho, this species grows from 610 to 2135 m (2000 to 7000 ft) and does best on moist sites.
plants
seed
Container (plug)
90 ml (5 cu in) plugs
9 Months
Height: 15 cm Root collar diameter: >2.5 mm Roots: Firm root plug
We generally buy our seeds on the open market. Ponderosa pine usually begins to bear cones around 20 years of age with small crops annually and large crops every 5 to 7 years. Seeds may be transferred 229 m (750 ft) in elevation and 0.75 degrees latitude (Rehfeldt 1980).
Seeds per kg range from 18,700 to 26,500 with a mean of 22,000 (8500 to 12,000/lb; mean = 10,000). Purity is 99%. Viability is usually high (90%+).
We bleach-treat seeds before stratification. For production lots, we place no more than 0.25 kg (0.5 lb) of seeds into a mesh bag and soak it in a 40% bleach solution (2 parts common laundry bleach (5.25% sodium hyploclorite) to 3 parts tap water) for 10 min with hand agitation (wear gloves and eye protection)(Wenny and Dumroese 1987). We rinse seeds thoroughly to remove bleach and allow them to "soak" in a running water bath for 48 hrs. Mesh bags are then hung within plastic bags inside a cooler set at 1 to 2 C (33 to 36 F) for 40 to 60 days. After stratification, we rinse seeds for 24 hrs in a running water bath, spin dry them to remove excess moisture, and allow them to air dry so the seed coats are not shiny.
Our crops are grown in fully-controlled greenhouses. Before sowing, the houses are thoroughly cleaned (walls, benches, floors, lights). We sometimes use copper sulfate or bleach on the floors and walls to kill moss and algae. We use traveling-boom irrigation, a double-head Smith 1:100 injector, natural gas heaters, and evaporative cooling. Crops are grown on permanently-placed rolling benches.
We use styrofoam containers: 160 cavities per container (756 cavities/m2 [71/ft2]); 90 ml (5.5 in3) volume; 15 cm deep (6 in) and 3 cm (1.2 in) wide; interiors of the cavities coated with copper. Containers are filled with a 1:1 (v:v) sphagnum peat moss:vermiculite medium having a pH around 4.2. We sow 1 to 4 seeds per cell depending on anticipated germination capacity. Seeds per cell are determined usingthe techniques of either Schwartz (1993) or Wenny (1993). After sowing, seeds are covered with a shallow layer of grit (6 mm [0.25 in] deep) and the containers moved to the greenhouse where they are immediately moistened with water (acidified to a pH around 6.0) until the medium is saturated. We generally refrain from pesticide applications, using cultural practices to inhibit problems associated with damping-off. We've found that using 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 keeps damping-off nearly non-existent at our facility. Day-time temps: 24 to 27 C (75 to 80 F). Night-time temps: 18 C (65 F). Once seedcoats begin to fall off germinating seedlings, we thin to one seedling per cavity, begin fertilization, and start photoperiod control. Nutrients are supplied about twice a week. We use Peters Conifer Starter (7N:40P2O5:17K2O) and CAN-17 (liquid ammonium calcium nitrate [17N]) to supply 42 and 81 ppm N, respectively, along with micros (Fe, B, MgSO4). We use phosphoric acid to keep pH of irrigation water around 6.0. We try to irrigate when blocks weigh 80% to 85% of saturated weight. Photoperiod is intermittent all-night-lighting (see Landis and others 1992; p 108) using 300 watt incandescent (15 min on/off cycles) providing about 500 lux at tree canopy height. We are having increasing problems with Lygus during this period. We have a no-tolerance policy on this insect and use Diazinon to control them.
6 to 8 weeks
Nutrients are supplied about twice a week. We use Peters Conifer Grower (20N:7P2O5:19K2O) and CAN-17 to supply 60 and 81 ppm N, respectively, along with micros (Fe, B, MgSO4). We use phosphoric acid to keep pH of irrigation water around 6.0. Day-time temps: 24 to 27 C (75 to 80 F). Night-time temps: 18 C (65 F). We try to irrigate when blocks weigh 80% to 85% of saturated weight, but slowly decrease the percentage so that by the time we wish to initiate buds, we irrigate at about 70% saturated weight. Photoperiod control is continued. When seedlings reach 11 cm in height we leach the medium with copious amounts of irrigation water and begin the hardening process.
6 to 8 weeks
Bud initiation: Micronutrients (Fe, B, MgSO4) are supplied every irrigation, but N is only supplied every other irrigation using CAN-17 at 40 ppm N. We use phosphoric acid to keep pH of irrigation water around 6.0. Day-time temps: 24 to 27 C (75 to 80 F). Night-time temps: 18 C (65 F). We try to irrigate when blocks weigh 65% to 75% of saturated weight. Photoperiod is discontinued. Post bud-initiation: Once buds are present (3 to 4 weeks after initiation), we use Peters Conifer Finisher (4N:25P2O5:35K2O) and CAN-17 to supply 12 and 81ppm N, respectively, along with micros (Fe, B, MgSO4). We use phosphoric acid to keep irrigation water pH around 6.0. Every 2 weeks we apply Peters Foliar Fertilizer (27N:15P2O5:12K2O) at 940 ppm N (3 passes with the traveling boom irrigation system; just enough application to wet entire crown). We try to irrigate when blocks weigh 75% of saturated weight. Temperatures are allowed to go to ambient, but we try to keep them under 27 C (80 F) during the day. Seedlings are ready for planting by mid-September. From mid-September until pack-out, we try and maintain day temperatures as cool as possible and prevent night temperatures from dropping below -2 C (28 F).
18 to 22 weeks
Seedlings are extracted for storage in late November through December. Seedlings are well-watered before removal but we allow foliage to dry before packing. Seedlings are placed within plastic bags inside waxed boxes or plastic tubs and stored at -2 to 0 C (28 to 32 F)(we want the plugs just barely frozen). Seedlings are monitored for storage mold problems. We prevent storage molds 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. We ship via UPS and only early in the week so seedlings don't sit in a warehouse over the weekend.
1 to 5 months
Landis TD; Tinus RW; McDonald SE; Barnett JP. 1992. The container tree nursery manual, volume 3. Atmospheric environment. Washington (DC): USDA Agriculture Handbook 674. 145 p.
Rehfeldt GE. 1980. Genetic gains from tree improvement of ponderosa pine in southern Idaho. Ogden (UT): USDA Forest Service Intermountain Research tation. Research Note INT-300. 4 p.
Schwartz M. 1993. Germination math: calculating the number of seeds necessary per cavity for a given number of live seedlings. Tree Planters' Notes 44(1):19-20.
Wenny DL. 1993. Calculating filled and empty cells based on number of seeds sown per cell: a microcomputer application. Tree Planters' Notes 44:49-52.
Wenny DL; Dumroese RK. 1987a. Germination of seeds surface sterilized with bleach. Tree Planters' Notes 38(3):18-21.
Wenny DL, Dumroese RK. 1987b. A growing regime for containerized ponderosa pine seedlings. Moscow (ID): University of Idaho, Idaho Forest, Wildlife and Range Experiment Station. Bulletin 43. 9 p.
Wenny, David L; Dumroese, Kasten. 2001. Propagation protocol for production of Container (plug) Pinus ponderosa Laws. plants 90 ml (5 cu in) plugs; University of Idaho - Center for Forest Nursery and Seedling Research Moscow, Idaho. In: Native Plant Network. URL: https://NativePlantNetwork.org (accessed 2024/05/16). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.
