Pinus (monophylla)

Alexandra Urza Research Ecologist USDA FS - Rocky Mountain Research Station 920 Valley Rd Reno, Nevada 89512 alexandra.urza@usda.gov www.fs.fed.us/rm/boise

---

Family Scientific Name:	Pinaceae
Family Common Name:	Pine family
Scientific Name:	Pinus monophylla Torr. & Frem.
Species Code:	PINMON
General Distribution:	Pinus monophylla is widespread throughout the Great Basin and in upper-montane environments of the Mojave Desert (throughout Nevada, eastern and southern California, northwestern Arizona, western Utah, and southwest Idaho). It commonly co-occurs with Juniperus species and is generally found in areas receiving 200–460 mm of annual precipitation and ranging in elevation between 1000 and 2800 m.
Propagation Goal:	Plants
Propagation Method:	Seed
ProductType:	Container (plug)
Stock Type:	983 mL container (2.7” x 14” heavyweight deepot cells)
Time To Grow:	7 to 10 months
Target Specifications:	Well developed root system
Propagule Collection:	Seeds are wild collected using an extended pruner when seeds are fully mature but cones are still closed and green, typically during September. Cones are kept separated according to site and elevation.
Propagule Processing:	Cones are opened in trays on a warm greenhouse benchtop. Once opened, seeds that have not fallen into the trays are extracted by hand. Discard seeds with holes or cracks, or any that are much smaller than the rest. Unfilled seeds are sorted out by bouncing seeds on a hard surface. When bounced, filled seeds have a lower-pitched sound and unfilled seeds have a higher-pitched, metallic sound. Seeds are refrigerated (2–4°C) if use is expected within 12 months.
Pre-Planting Treatments:	Imbibing/flushing: Imbibe seeds by soaking in water at room temperature for 36-48 hours. Flush with clean water every 4-8 hours to rinse away pathogens. Remove seeds from water bath and surface dry on clean paper towels. Cold, moist stratification: Stratify seeds in wetted vermiculite at 1–5°C for 50-65 days. We use a ratio of roughly 3:1 vermiculite:water (2,800 mL vermiculite to 1,000 mL water). The goal is to have moist substrate, but not so wet that water pools up. Seeds are placed into clean organza mesh bags before placing in moistened vermiculite in sealed plastic bags or totes, making it easier to separate and extract seed lots. Check seeds weekly and discard moldy seeds. Seeds are planted when about 10% have radicles emerging.
Growing Area Preparation/ Annual Practices for Perennial Crops:	Propagation environment: Seedlings are grown in a climate-controlled greenhouse, and temperatures are maintained between 12 and 27 °C. No supplemental light is provided. Soils: For our research purposes, we have successfully used two different soil mixes: (1) a soil mix that resembled native soils from pinyon-juniper woodlands (coarse-textured topsoil amended with humus); and (2) a standard potting mix consisting of one-third each of local topsoil, sand, and peat moss. For the second soil, the seedlings were given a one-time fertilization with Miracle-Gro plant food. Container type and volume: 2.7” x 14” (983 mL) heavyweight deepot cells (D60H, Stuewe & Sons, Inc.). Deep containers are important for taproot development; however, smaller diameter containers of the same depth may be adequate and would facilitate easier field outplanting by reducing filled container weight. Irrigation method: Inverted rotor spray mini sprinklers are mounted 3-5 ft (1–1.5 m) above the seedlings. These create a fine mist that ensures even water distribution.
Establishment Phase:	Seeds are sown in early spring, into semi-moist soils. Plant 1 or 2 seeds in each container cell to a depth of 3 cm (~1”). Place the seed in the hole with the pointed side down. If the radicle is emerging from the seed, dig the hole deep enough to accommodate the radicle and be careful not to break it. Cover the seed with soil. The top of the seed should be approximately 1-2 cm under the surface. For the first two weeks, mist/water daily to keep soils moist as seedlings emerge. Then, water whenever soils appear to be drying out, approximately twice weekly.
Length of Establishment Phase:	4 to 6 weeks
Active Growth Phase:	After establishment, watering frequency is reduced, giving enough time for the soils to dry down moderately between irrigations. Soil water content is used to determine how frequently to irrigate, because many conditions (e.g. soils, pot size, temperature, irrigation method) affect how quickly soils will dry out. We use the “scientific” method described here: https://www.fs.fed.us/rm/pubs_journals/2015/rmrs_2015_dumroese_k001.pdf. We found that the optimal range of soil moisture was approx. 15-28% GWC (gravimetric water content), which for our experiments was achieved by irrigating about once every 5–10 days. We found that the wetter end of this soil moisture range produces larger seedlings, but the drier end produces seedlings that survive slightly better once planted outside.
Length of Active Growth Phase:	4 to 6 months
Hardening Phase:	Starting in late August, gradually move the conditions in the greenhouse towards outside conditions. Lower the nighttime low temperatures by a few degrees each night, while daytime highs can remain as-is. After a couple weeks of changing greenhouse conditions, move the seedlings to a shade house or another shady outdoor location. Reduce watering frequency to every 1-2 weeks.
Length of Hardening Phase:	6 to 10 weeks
Harvesting, Storage and Shipping:	If planting in fall, move to the field planting location 1-2 weeks prior to planting, usually early October. Store in shade and insulate the root zone by wrapping groups of container trays with rolled tarps or similar.
Outplanting performance on typical sites:	Outplanting timing: Planting typically occurs in the fall, mid- through late-October, before snowfall and when temperatures are still sufficient to stimulate root growth. Planting microsite selection: Seedlings are typically planted on the shaded side of a shrub (north/northeast/east sides), as far under the shrub canopy as feasible. Remove lower branches of the shrub as needed but retain as much canopy structure as possible. If no suitable shrubs are available, as may be the case for a recently burned area, locate seedlings on the shaded side of a log or large fragment of wood. Make sure the woody fragment is large enough to sufficiently shade the seedling, while considering its future height growth. Forestry shade cards can be used in situations where shrubs or large wood are not available, although these are not preferable in areas that receive heavy winter snow. For restoration purposes, plant seedlings no closer than 16” (40 cm) from each other. Planting method: Holes are augered using a handheld drill with auger bit attachment (depth and diameter ≥ 2” greater than container). Hand trowels are used to remove loose dirt from the bottom of each hole. Approx. 1 liter of water is poured into holes and allowed to soak in before planting. Having a moist, but not wet, soil core is helpful to keep it intact, but seedlings that bare-root during the planting process usually fare well. After planting, a thin layer (no more than ½” deep) of plant litter is added to the soil surface, which improves seedling survival. Replace disturbed soil and litter as much as possible in the vicinity of each planted seedling, to avoid attracting herbivorous small mammals that directly damage the seedlings by stem girdling or may be attracted to dig their own burrows in the loose soil that is created by excavation and planting. Post-planting irrigation: Seedlings are watered immediately after planting, adding approx. 1 liter of water to each seedling. Ambient precipitation is monitored during the first year after planting, and seedlings are watered periodically (every 2–4 weeks if feasible) during dry periods. Seedlings are typically not watered beyond the first year after planting.
Other Comments:	This protocol was developed for smaller-scale research (up to 3,500 seedlings produced at one time). Many of the methods would need to be updated before applying to larger-scale propagation efforts.
References:	Vasey, G.L., Urza, A.K., Chambers, J.C., Pringle, E.G., and Weisberg, P.J. 2023. Clinal variations in seedling traits and responses to water availability correspond to seed-source environmental gradients in a foundational dryland tree species. Annals of Botany 132(2): 203–216.

Citation:

Urza, Alexandra; Chambers, Jeanne; Vasey, Georgia; Weisberg, Peter. 2025. Propagation protocol for production of Container (plug) Pinus monophylla Torr. & Frem. Plants 983 mL container (2.7” x 14” heavyweight deepot cells); USDA FS - Rocky Mountain Research Station Reno, Nevada. In: Native Plant Network. URL: https://NativePlantNetwork.org (accessed 2025/02/24). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.