Pinus ponderosa Douglas ex P. Lawson & C. Lawson

Tree, Evergreen, Monoecious, Habit erect, Trees without or rarely having knees, Tree with bark rough or scaly, Young shoots 3-dimensional, Buds resinous, Leaves needle-like, Leaves alternate, Needle-like leaf margins finely serrulate (use magnification or slide your finger along the leaf), Leaf apex acute, Leaves > 5 cm long, Leaves < 10 cm long, Leaves > 10 cm long, Leaves yellow-green above, Leaves yellow-green below, Leaves not blue-green, Needle-like leaves somewhat rounded, Needle-like leaves twisted, Needle-like leaf habit erect, Needle-like leaves per fascicle mostly 2, Needle-like leaves per fascicle mostly 3, Needle-like leaf sheath persistent, Twigs glabrous, Twigs viscid, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones > 5 cm long, Seed cones bearing a scarlike umbo, Umbo with obvious prickle, Bracts of seed cone included, Seeds brown, Seeds yellow, Seeds winged, Seeds unequally winged, Seed wings prominent, Seed wings equal to or broader than body.

Ponderosa pine is propagated by seed. Cones are ready for collection in October and November when they turn reddish brown. Mature seed is firm and brown in color. Cones should be dried on canvas tarp in a well-ventilated area immediately after they have been collected. The seeds will drop from the cones as they dry.

Several germination methods for ponderosa pine have been utilized, each with their own variations. In general, seeds undergo an imbibation treatment before stratification. Seeds are placed in mesh bags and soaked in cold running water for 48 hours. One variation is to soak the seeds in a 40% bleach solution for 10 minutes with hand agitation prior to placing them under running water. The mesh bags are place in plastic bags and stored at 1^oC for 2 to 8 weeks. They should be checked daily for mold. Seeds are sown into containers and covered with media. The media should be kept moist throughout germination. Germination will occur at an average greenhouse temperature of 20^oC. Alternating greenhouse temperatures of 21-25^oC during the day and 16-18^oC at night is an appropriate environment for germinating seeds. Germination will occur in approximately 15 days.

Seedlings are thinned and watered daily throughout the establishment phase. They should not be moved outdoors until after the last frost of the year.

Seeds can be dried to between 5 and 8% moisture and placed in airtight plastic bags, then stored for long periods of time in freezers set at –15^oC.

Ponderosa pine grows to impressive size. Stems  263 cm (103.5 in) in d.b.h. and 70.7 m (232 ft) in height have been  recorded (13). Diameters at breast height of 76 to 127 cm (30 to 50 in)  and heights of 27.4 to 39.6 m (90 to 130 ft) are common throughout most of  its range. Trees often reach ages of 300 to 600 years.

    Diameter growth can be rapid and remain fairly constant for long periods  provided trees are given adequate growing space. In California, on  productive sites, free-growing trees can reach 66 cm (26 in) in d.b.h. in  30 years or 22 cm. (8.7 in) per decade (data on file at Pacific Southwest  Forest and Range Experiment Station, Redding, CA). In central Oregon,  where sites are less productive, trees 13 to 51 cm (5 to 20 in) in d.b.h.  and from 19 to 36 years old can grow 12 cm (4.9 in) in d.b.h. per decade  if free of intertree competition (3). Trees in a virgin stand in Arizona  grew 29 mm (1.14 in) on the average during a 10-year period, but trees in  a cutover stand grew 43 mm (1.68 in) (55).

    Vegetative competition can restrict diameter growth markedly whether it  be from neighboring trees or understory shrubs. In the central Oregon  study, trees completely surrounded by understory shrubs grew only 9 cm  (3.5 in) per decade. Those trees with no competitive ground cover averaged  12 cm (4.7 in) of growth per decade. In California on a droughty, skeletal  soil, severe shrub competition reduced diameter growth to less than half  that of competition-free trees. Insect damage, which was greater on the  trees competing with shrubs, accounted for some of the growth depression  (44). Stagnation in diameter, and often in height, represents a serious  problem in densely stocked stands throughout the species' range, but  especially on poor sites.

    Height growth is most rapid in the pole and young sawtimber size classes  to about 60 years. In the Pacific Northwest, dominant trees in stands of  moderate density grow from 0.24 to 0.46 m (0.8 to 1.5 ft) annually between  the ages of 20 to 60 years on timber-producing sites (2). Rate of growth  declines gradually at older ages. Arizona trees of 160 years or older  (determined at breast height) grow little in height (55). Height growth  increases with site productivity and is more sensitive to stand density  than was once believed.

    Representative yields of ponderosa pine from a normal yield table for  sites of various productivities are given in table 1 (39). For extensive  natural stands, table values should be reduced by 25 percent or more  because of roads, rock outcrops, steep slopes, openings, and other  unproductive areas.

    Table 1- Total volume inside bark of ponderosa pine 1.5  cm (0.6 in) and larger in d.b.h. (39)            Site index at base age  100 years¹              Age   18 m or 60 ft  27 m or 90 ft  37 m or 120 ft  46 m or 150 ft            yr  m³/ha        20     28    94  168    262        40  122  238  396    588        60  192  340  570    861        80  238  413  696  1060      100  273  472  794  1204      120  308  518  868  -      140  336  556  928  -      yr  ft³/acre        20     400  1,350    2,400    3,750        40  1,750  3,400    5,650    8,400        60  2,750  4,850    8,150  12,300        80  3,400  5,900    9,950  15,150      100  3,900  6,750  11,350  17,200      120  4,400  7,400  12,400  -      140  4,800  7,950  13,250  -      ¹Height of  dominant and codominant trees of average d.b.h.        Old-growth ponderosa pine produces clear, high-grade lumber, but young  trees typically are limby. Natural pruning develops slowly. An average  clear length of only 3.5 m (11.5 ft) was recorded in 250-year-old stands  in central Idaho (13).

Habitat and Ecology

Systems

• Terrestrial