Natural regeneration is difficult to  achieve, primarily because of unfavorable climatic conditions, but seed  predation and heavy grazing pressure, especially by sheep and goats, also  play a role (67). Although pinyon grows best in full sunlight and can  germinate in the open, seedlings must be protected from the harsh  environment (21,31,35,46,49). Regeneration is usually achieved in the  shade of tree canopies, under shrubs such as rabbitbrush,  mountain-mahogany, and sagebrush, or alongside fallen trees.

    Optimum germination temperature for pinyon seed is about 21° C (70°  F). Germination is epigeal (68). Preliminary studies indicate that  germination can be significantly improved by washing seeds for 48 hours in  running tap water. Cold stratification for 30 or 60 days increases speed  of germination but not the percentage. Treatment with hydrogen peroxide to  suppress mold and enhance germination generally is not effective. Seeds  germinate in spring and summer following dispersal, depending on soil  moisture and temperature, with summer germination coinciding with the  onset of the rainy season. Also, seedling establishment probably depends  on an adequate moisture supply during the first summer (29,30,54,66,68).  Growth throughout the seedling stage is extremely slow, often with only  primary needles developing the first year, and subsequent height growth  averaging 2.5 to 5.0 cm (1 to 2 in) per year (67).