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The growing season of singleleaf pinyon is affected by winter cold, summer heat, and severe water deficits. Tree growth usually starts in April and ceases in September or October. During most of this time, trees depend on moisture stored by winter precipitation. Male and female strobili emerge from buds formed the previous summer in late spring or early summer. |
 Staminate cones |
 Old ovulate cones |
Small cones emerge during this period of summer growth and spread their scales. Staminate cones, usually by mid-June, shed pollen which sifts into ovulate cones by means of the wind. Once pollenated the ovulate cones close. Cones develop slowly the 1st growing season, being 1/4th their mature size by September, and pass the winter this way. The following spring, the yearling cone starts to grow again, the pollen grains inside fertilize the egg cells, and the process of seed formation begins, about 1 year after pollination. Cones grow rapidly throughout the summer of the 2nd growing season, the seeds maturing in late summer. Cones mature and dry in early September and turn from green to brown. The scales part and the seeds are displayed in September to November, depending on environmental conditions and elevation. |
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