Pinus sabiniana occurs at elevations between 150 and 1500 meters. The bioregional distribution is throughout the California Floristic Province (except extreme northern Northwestern California, northern Cascade Range, San Joaquin Valley); it also occurs in the western Great Basin Floristic Province and in the western deserts of California. This tree is found most often on dry rocky habitats in such varied plant communities as foothill woodland, northern oak woodland, chaparral and infertile soils in mixed-conifer and hardwood forests

This pine can attain a height of of to 38 meters, with a trunk occasionally as large as two meters in diameter. Bark is dark gray with irregular furrows, forming yellow plates when very old. The needles occur as three per bundle, nine to 38 cm in lehgtn; the fragrant foliage is gray-green. The brownish ovate-oblong seed cones are pendant, ten to 28 cm. Scale tip is reflexed, elongated and angled; seeds are winged.

Pinaceae -- Pine family

    Robert F. Powers

    Digger pine (Pinus sabiniana), also called bull pine or gray  pine, has limited commercial use today, but it once was important to  California Indians, who used its seeds and parts of cones, bark, and buds  as food supplements, and its twigs, needles, cones, and resin in basket  and drum construction (23,30). Indians and early settlers used the resin  of Digger pine for medicinal purposes. During California's gold rush  period, from 1848 to 1860, all foothill timber, including Digger pine, was  heavily used for fuel and structural materials. Despite these uses, Digger  pine was viewed with contempt by many early settlers who placed slight  value on a tree that provided little shade and poor lumber. In fact, the  term "Digger" stems from a contemptuous name given by early  settlers to the many small Indian tribes once occupying central  California.

General: Pine Family (Pinaceae). This native tree reaches 38 m in height with a trunk less than 2 m wide. The gray-green foliage is sparse and it has three needles per bundle. Each needle reaches 9-38 cm in length. The trunk often grows in a crooked fashion and is deeply grooved when mature. The seed cone of gray pine is pendent, 10-28 cm, and opens slowly during the second season, dispersing winged seeds.

foothill pine, bull pine, digger pine, California foothill pine

Gray pine is endemic to California. It is distributed from Siskiyou
County south through the foothills of the Klamath, Cascade, and Coast
Ranges and the Sierra Nevada to Ventura County [23,39,40]. Near its
southernmost Sierra Nevada limit, gray pine is absent from a 55-mile
(89-km) stretch between Kings River and the South Fork of the Tule River
[23].

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

3 Southern Pacific Border
4 Sierra Mountains
7 Lower Basin and Range

CA

A California endemic, Digger pine grows between latitude 34° 30'  and 41° 15' N. Generally found between elevations of 300 to 900 m  (1,000 to 3,000 ft) in dry foothill woodland communities of California's  Central Valley, natural stands of Digger pine also grow from as low as 30  m (100 ft) at several locations on the floor of the Sacramento Valley to  almost 2130 m (7,000 ft) near Sawtooth Peak in Inyo County (10). Digger  pine is found in the Coast and Cascade Ranges, Klamath Mountains,  southwestern Modoc Plateau, western Sierra Nevada, and Tehachapi  Mountains, and over a broad environmental sweep, from the westerly edge of  the Mojave Desert, to the Santa Lucia Mountains in Monterey County within  sight of the Pacific surf (6). Digger pine is absent in a conspicuous  89-km (55-mi) gap near its southern Sierra Nevada limit. The cause of the  gap is unknown but was noted as early as 1865 (10).

     
- The native range of Digger pine.

Pinus sabiniana Douglas ex D. Don:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

It ranges in parts of the California Floristic Province, the western Great Basin and western deserts. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Establishment

Adaptation: This tree is found in the foothill woodland, northern oak woodland, chaparral, mixed conifer forests and hardwood forests from 150-1500m.

Extract seeds from the cones and gently rub the wings off, and soak them in water for 48 hours, drain them, and thoroughly surface-dry. Put seeds in a plastic bag, without any medium, seal the bag and place them in refrigerated conditions until their chilling treatment begins. Allow three times the air space as seed space in the bag. It is best to sow the seeds in May and therefore, expose the seeds to a chilling treatment of at least sixteen weeks prior to sowing. After cold stratification, plant the seeds in a well-drained coarse potting mix in leach tubes that are narrow but deep with two seeds per tube. These containers should allow roots to reach the air and stop growing and be at least 6 inches deep. Fertilize the containers with a starter formulation of fertilizer with low or zero nitrogen. These containers can be kept in a greenhouse for the first 4 to 6 weeks, receiving 70-degree temperatures during the day. Keep the surface of the soil moist during the germination phase. Next after the first set of cotyledons, water the plants with a deep, thorough soaking and let the plants dry in between watering. Thin the plants down to one per container and move the pots into a shade-house with 30 percent shade after 4 to 6 weeks. Protect the plants from wind and wildlife. During the main summer growing season use a balanced fertilizer applied to each container. At the end of the growing season use a finisher formulation of fertilizer. Plant the plants in the ground outside in the late winter or early spring in moist soil. Conduct supplemental hand watering or irrigation if the rains are insufficient. Clear weeds in a 3 feet by 3 feet area around the plants to encourage better survival and growth rate. Make sure a protective barrier is placed around the conifers such as vexar tubing to shield them from jack rabbits, deer and other wildlife that may feed on the leaves, stems, and roots.

Trees to 25m; trunk to 1.2m diam., straight to crooked, often forked; crown conic to raggedly lobed, sparse. Bark dark brown to near black, irregularly and deeply furrowed, ridges irregularly rectangular or blocky, scaly, often breaking away, bases of furrows and underbark orangish. Branches often ascending; cone-bearing branchlets stout, twigs comparatively slender, both pale purple-brown and glaucous, aging gray, rough. Buds ovoid, red-brown, ca. 1cm, resinous; scale margins white-fringed. Leaves mostly 3 per fascicle, drooping, persisting 3--4 years, 15--32cm ´ 1.5mm, slightly twisted, dull blue-green, all surfaces with pale, narrow stomatal lines, margins serrulate, apex short-acuminate; sheath to 2.4cm, base persistent. Pollen cones ellipsoid, 10--15mm, yellow. Seed cones maturing in 2 years, shedding seeds soon thereafter, persisting to 7 years, pendent, massive, heavy, nearly symmetric, ovoid before opening, broadly to narrowly ovoid or ovoid-cylindric when open, 15--25cm, dull brown, resinous, stalks to 5cm; apophyses elongate, curved, continuous with umbos to form long, upcurved claws to 2cm. Seeds narrowly obovoid; body ca. 20mm, dark brown; wing broad, short, ca. 10mm. 2n = 24.

More info for the term: fresh

Gray pine is a drought-tolerant, native evergreen conifer. Mature
trees average from 40 to 80 feet (12-24 m) in height and from 12 to 36
inches (30-90 cm) in d.b.h. [38,40]. Trees usually maintain a pyrimidal
growth form until the pole stage. Mature trees typically have multiple
trunks [40]. Gray pine is self-pruning, and lower branches are often
a considerable distance above the understory [35]. Gray pine grows a
deep taproot where soil depth permits [4,40]. In hardpan soils, it
develops a spreading, shallow root system with a weak taproot extending
through the duripan [40]. The bark of young trees is thin [40], while
older trees have thick bark [35]. Needles grow from 8 to 12 inches
(20-30 cm) long and are shed every 2 to 3 years [39]. Gray pine's
heavily spined female cones are among the largest and most massive in
the genus. Fresh cones average from 0.7 to 1.5 pounds (0.3-0.7 k), and
may exceed 2.2 pounds (1 kg) [40]. The cones are typically from 6 to 12
inches (15-30 cm) long. They do not form an abscission layer and are
retained long after seeds are shed. The hard-coated, heavy seeds are
from 0.6 to 1.0 inch (15-25 mm) long and have short-winged seeds
[17,38,39]. The lifespan of gray pine is unclear because most older
specimens were cut by early settlers, but it is believed to be 200+
years [40].

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 blue-green, Needle-like leaves triangular, Needle-like leaves twisted, Needle-like leaf habit drooping, 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 winged, Seeds unequally winged, Seed wings narrower than body.

More info for the terms: codominant, cover, density, hardwood, shrub, shrubs, tree

Gray pine and blue oak (Quercus douglasii) occur together over much of
California's oak woodlands. The blue oak-gray pine community varies in
stand density and composition, often sharing dominance with several
other tree species. The understory may be mostly grasses, shrubs, or
mixtures of both [16]. Pure stands of gray pine occur in localized
areas of serpentine soil [21], but more often, blue oak provides more
cover within the community type. At lower elevations, the blue oak-gray
pine woodland grades into chaparral, valley oak (Q. lobata) woodland, or
Oregon white oak (Q. garryana) woodland. At higher elevations, it mixes
with California black oak (Q. kelloggii) or ponderosa pine (Pinus
ponderosa) forest [16,26]. In its easternmost distribution, gray pine
merges with desert communities such as western juniper (Juniperus
occidentalis) and big sagebrush (Artemisia tridentata) near the Great
Basin and singleleaf pinyon (P. monophylla)-California juniper (J.
californica) near the Mojave Desert [16].

Plant associates: Overstory associates not mentioned in Habitat Types
and Plant Communities or SAF Cover Types include Coulter pine (P.
coulteri), California buckeye (Aesculus californica), interior live oak
(Quercus wislizenii), bigcone Douglas-fir (Pseudotsuga macrocarpa), and
MacNab cypress (Cupressus macnabiana) [3,11,18,26,43].

Common shrub associates include toyon (Heteromeles arbutifolia),
wedgeleaf ceanothus (Ceanothus cuneatus), chamise (Adenostoma
fasciculatum), California scrub oak (Q. dumosa), desert scrub oak (Q.
turbinella), California buckthorn (Rhamnus californicus), common
manzanita (Arctostaphylos manzanita), birchleaf mountain-mahogany
(Cercocarpus betuloides), poison-oak (Toxicodendron diversilobum),
Sargent cypress (Cupressus sargentii), and hollyleaf cherry (Prunus
ilicifolia) [2,3,11,24,26].

Common ground associates include slender oat (Avena barbata), California
buckwheat (Erigonum fasciculatum), soft chess (Bruomus hordeaceus),
ripgut brome (B. rigidus), cutleaf filaree (Erodium cicutarium), bur
clover (Medicago hispida), ground lupine (Lupinus bicolor), and tarweed
(Hemizonia spp.) [3,8,24].

Publications listing gray pine as a dominant or codominant species are
as follows:

A classification system for California's hardwood rangelands [2]
Blue oak communities in California [3]
Association types in the North Coast Ranges of California [12]
Natural terrestrial communities of California [26]

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: shrub

K005 Mixed conifer forest
K006 Redwood forest
K009 Pine - cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K023 Juniper - pinyon woodland
K024 Juniper steppe woodland
K028 Mosaic of K002 and K026
K029 California mixed evergreen forest
K030 California oakwoods
K033 Chaparral
K034 Montane chaparral
K035 Coastal sagebrush
K038 Great Basin sagebrush
K048 California steppe

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

More info for the term: shrub

FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES27 Redwood
FRES28 Western hardwoods
FRES29 Sagebrush
FRES34 Chaparral - mountain shrub
FRES35 Pinyon - juniper
FRES42 Annual grasslands

Gray pine grows on exposed, dry, rocky slopes at elevations from 100
to 6,000 feet (30-1,800 m) [23,26]. The climate is Mediterranean, with
mild winters and hot, dry summers [35]. Annual mean precipitation is 21
inches (530 mm), ranging from 3 to 40 inches (76-1,000 mm) [6,40].
Eighty percent of precipitation occurs during winter and early spring.
Snow falls occasionally [35]. The annual mean temperature is 61 degrees
Fahrenheit (16 deg C), with maximum summer temperatures sometimes above
105 degrees Fahrenheit (41 deg C) [6,9]. Relative humidity is often 5
percent or lower in summer [9].

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

233 Oregon white oak
234 Douglas-fir - tanoak - Pacific madrone
238 Western juniper
239 Pinyon - juniper
244 Pacific ponderosa pine - Douglas-fir
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
248 Knobcone pine
249 Canyon live oak
250 Blue oak - Digger pine
255 California coast live oak

Digger pine grows on soils in five soil orders (Alfisol, Entisols,  Inceptisols, Mollisols, and Ultisols) derived from a wide variety of  geologic materials including granodiorite, dacite, andesite, basalt,  peridotite, greenstone, schists of various types, limestone, river  gravels, and sandstone. The striking feature in much of Digger pine's  range is its association with ultramafic soils, particularly those formed  from serpentinite. Inclusions of serpentinite or limestone in upland zonal  soils produce nutritional imbalances that allow Digger pine to persist  within the mixed-conifer forest of the Sierra Nevada and the  conifer-hardwood forest of the north Coast Ranges (6).

    Soils supporting stable populations of Digger pine characteristically  have low levels of available moisture. Even on sites where soil moisture  is relatively high, Digger pine tends to dominate only the shallowest  phases. Although found on deep, alluvial valley terraces, Digger pine has  been eliminated systematically from many fertile sites by stockmen seeking  to increase grass production (6,18,30). Today, many of the sites still  supporting Digger pine consist of dry rolling hills, rocky slopes, and  steep canyon walls. Few conifer species can match Digger pine's ability to  persist under such xeric, sterile conditions.

Temperatures characterizing Digger pine's range span the gamut of  coastal to Great Basin climates. Yearly means vary from 10° to 17°  C (50° to 62° F), with mean minima of -2° to 3° C (28°  to 37° F), in the coolest months, and mean maxima of 31° to 36°  C (88° to 97° F) in the warmest months (30). Individual summer  days often exceed 38° C (100° F). Few tree species grow over as  wide a range in precipitation as Digger pine, with annual averages varying  from 250 mm (10 in) at the edge of the Mojave Desert to 1780 mm (70 in) at  its upper limits in the Sierra Nevada (6). Sites receiving as little as 80  mm (3 in) of precipitation in a single season continue to support stable  populations (30).

    Despite the apparent diversity in climatic tolerance shown by Digger  pine, four climatic conditions characterize most of its natural range:  hot, dry summers; absence of summer fog; precipitation, mostly as rain;  and generally mild winters. Digger pine's ability to withstand summer  drought and to photosynthesize during mild periods of winter and spring  give it a strong competitive advantage over many other species in the  California foothills.

Dry foothills on the west slope of the Sierra Nevada, and in the coast ranges, nearly ringing the Central Valley of California; 30--1900m; Calif.

Systems

• Terrestrial

Digger pine forms a part of variants of seven forest cover types (3) and  is a major component of an eighth, Blue Oak-Digger Pine (Society of  American Foresters Type 250), where together with blue oak (Quercus  douglasii) it forms a climax community in a nearly continuous band around  California's Central Valley between valley grasslands and montane forest  (21).

    Associated trees in the cover type Blue Oak-Digger Pine include  California buckeye (Aesculus californica), California scrub oak  (Quercus dumosa), California black oak (Q. kelloggii), and  interior live oak (Q. wislizeni) in the Sierra Nevada; and  California buckeye, coast live oak (Q. agrifolia), California  black oak, and valley oak (Q. lobata) in the Coast Ranges. Digger  pine also grows with western juniper (Juniperus occidentalis) in  the Pit River drainage of the Modoc Plateau, and Coulter pine (Pinus  coulteri) in the southern Coast Range. Predominant shrubs include  several manzanita (Arctostaphylos) species, primarily A.  manzanita and A. viscida, buckbrush (Ceanothus cuneatus),  redbud (Cercis occidentalis), birchleaf mountain -mahogany  (Cercocarpus betuloides), silktassel (Garrya fremontii), toyon  (Heteromeles arbutifolia), hollyleaf buckthorn (Rhamnus  crocea), and western poison-oak (Toxicodendron diversilobum).

    Digger pine also grows on ultramafic and calcareous soils within several  forest types, including Redwood (Type 232) west of Healdsburg, and at the  low elevational fringe of Douglas-Fir-Tanoak-Madrone (Type 234) and  Pacific Ponderosa Pine-Douglas-Fir (Type 244). Within Pacific Ponderosa  Pine (Type 245), Digger pine is found on westerly slopes of the southern  Cascades and northern Sierra Nevada. The species also grows in low  elevational fringes of California Black Oak (Type 246), Knobcone Pine  (Type 248), and in portions of Canyon Live Oak (Type 249) and Western  Juniper (Type 238) (3).

Because of the species' ability to grow  throughout the winter, succulent shoots of Digger pine are damaged easily  by sudden frosts after periods of mild temperature. Digger pine also is  particularly susceptible to damage by wind and hail (31). On sites where  winter temperatures fluctuate greatly, stable populations may have evolved  such adaptive strategies as delayed germination of seed (9). The thin bark  of young trees, along with the species' high resin content and the  presence of congealed flows that have dripped from wounds, make Digger  pine susceptible to severe damage by fire.

    Prominent diseases of Digger pine include western gall rust (Peridermium  harknessii) and dwarf mistletoe (Arceuthobium occidentale). Western  gall rust forms branch galls on Digger pine throughout its range but  rarely causes appreciable damage or death. Dwarf mistletoe is a  particularly damaging disease that is widely distributed in even the most  open stands (12,26). Once infection is established, dwarf mistletoe  spreads rapidly (11). Growth loss, deformity, and death often result with  the buildup of the disease, and trees of all sizes are susceptible. Digger  pine also is susceptible to Heterobasidion annosum root disease.  This pathogen seldom is a problem in open stands, although the disease can  spread rapidly in well stocked stands, such as plantations (1).

    Digger pine is host to a wide variety of cone, twig, and foliage insects  and is the specific host for Ips spinifer, an aggressive bark  beetle that often kills trees weakened by fire or drought (5). Heavy  production of resin by healthy trees provides a strong defense against  many bark beetles, and vapors from its resins are toxic to some (28).  Nevertheless, heavy production of resin favors a pitch nodule moth (Petrova  sabiniana), which pupates within resin nodules (5). Thick seedcoats  provide a protective barrier against damage from most seed insects, but  much of the seed production is consumed by rodents and birds. However,  predation does not seem to restrict Digger pine's range (32).

Gray pine is increasing in blue oak-gray pine communities due to fire
suppression and lack of blue oak regeneration [14]. Rangeland managers
are reporting an increase of chaparral brush invading grassy
understories of blue oak-gray pine woodlands, also because of fire
suppression [8]. Timber species are invading the woodlands as well
[26]. Prescribed burning would help restore the blue oak-Digger pine
community to a more desirable species balance. Managers, however,
should be alerted to the regeneration capacity of blue oak ecotypes
within their area. See the blue oak FEIS write-up for further
information.

Fire managers recommend broadcast burning of blue oak-gray pine
woodlands in spring after grasses have dried, usually late May, or in
fall after the first rains. Fires are set with drip torches and
permitted to burn downslope. There should be little or no wind.
Recommended relative humidity range during spring is 30 to 35 percent;
recommended ambient air temperature is between 70 to 80 degrees
Fahrenheit (21-27 deg C). In fall, recommended relative humidity is 25
to 30 percent. Fall temperatures of 70 to 75 degrees Fahrenheit (21-24
deg C) are suggested [1].

If the woodlands contain a chaparral understory, upslope strip burning
during winter and early spring is recommended. At this time, chaparral
brush is fully green and grass shoots are from 2 to 3 inches (0.8-1.2
cm) high. Acceptable ranges of humidity are from 25 to 30 percent;
acceptable temperature ranges are from 70 to 75 degrees Fahrenheit
(21-24 deg C) [1].

Dwarf-mistletoe is eliminated from an infected area following a
stand-replacing fire [31].

Bark beetles (Arhopalus asperatus) have been observed attacking severely
scorched gray pine within hours following fire [45].

More info for the terms: cover, density, severity, wildfire

Information regarding postfire recovery of gray pine is sparse. Keeley
[30] reported a gray pine seedling density of 133 per acre (54/ha)
following a wildfire of unreported severity at Bartlett Springs, Lake
County. Percentage cover provided by gray pine in a blue oak-gray pine
community often decreases when fires are frequent. Many blue oak
ecotypes sprout following fire, and under a regime of frequent fire,
rapidly growing blue oak sprouts interfere with gray pine seedling
growth [16,26].

Moderate-severity fire kills a substantial number of gray pine. The
prescribed fire in Glenville (see Fire Ecology or Adaptations) killed 83
percent of gray pine present. All surviving gray pine were large trees
[35].

More info for the terms: ground residual colonizer, root crown, secondary colonizer

Tree without adventitious-bud root crown
Ground residual colonizer (on-site, initial community)
Secondary colonizer - on-site seed
Secondary colonizer - off-site seed

More info for the terms: moderate-severity fire, natural, prescribed fire, severity

Fire is a natural component of the blue oak-gray pine community [1].
Historically, these woodlands burned at 15- to 30-year intervals [1].
Fires were typically intense but of light or moderate severity, with
vegetation and fuels extremely dry in summer [9,28]. Researchers at the
San Joaquin Experimental Range in O'Neals, California, noted fire
surface temperatures near woody vegetation of 1,200 degrees Fahrenheit
(650 deg C) in a blue oak-gray pine community with a mixed-grass and
sparse brush understory [28]. A prescribed fire in a blue oak-gray pine
community in Glenville, Kern County, generated subsurface temperatures
of 156 degrees Fahrenheit (69 deg C) at a depth of 2 inches (0.8 cm)
below ground [35].

Gray pine is highly flammable. The needles contain ether extracts
[5]. It is a heavy resin producer, with the wood, bark, cones, and
needle sheaths all containing pitch [35,40]. Congealed flows of resin
that have dripped from wounds are common on gray pine. Consequently,
it is susceptible to fire damage [40].

Gray pine has two adaptations which enable it to survive fire. First,
some large trees will withstand moderate-severity fire. Mature trees
with thick bark and self-pruned trunks are best able to avoid fatal
scorching [35]. Secondly, seed regeneration is favored following fire.
Fire creates a favorable bare mineral soil seedbed, and heat
scarification of the woody seedcoat increases germination rates [40].

More info on this topic.

More info for the term: climax

Blue oak-gray pine communities are fire climax and are replaced by
ponderosa pine or other coniferous forests in the absence of fire
[16,26,32]. Gray pine readily establishes from seed on disturbed sites
and is common in all seral stages of the blue oak-gray pine community
[30]. Young trees tolerate partial shade [40]. Mature trees are shade
intolerant [25].

Gray pine produces seed at 10 to 25 years of age [33]. It is a
consistent seed producer, with large crop outputs at 2- to 3-year
intervals [40]. Gray pine has delayed seed dispersal [10,46]. Cones
open slowly, shedding seed over a period of several months [40]. Seeds
are disseminated by animals, gravity, and water [1,40]. Scrub jay and
acorn woodpecker are the most effective animal disseminators [40].

Seeds require cold stratification for approximately 30 days prior to
germination [27,33]. The exact stratification period varies with
ecotype. Seedbank-stored seed remains viable for up to 5 years [33].
Germination rates improve when the seed is scarified and increase
greatly when the nuclear cap is removed [40,48]. Germination is epigeal
[33]. Seedlings establish best on bare mineral soil under partial
shade. Most first-year growth occurs in the taproot. Subsequent top
growth is rapid; early growth rates of gray pine are among the most
rapid of all conifers. Rate of top growth averages 28 inches (70 cm)
per year for the first 8 years of life [40].

Gray pine does not reproduce vegetatively [40].

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More info for the term: phanerophyte

Phanerophyte

More info for the term: tree

Tree

Beyond the seedling stage, Digger pine  is one of the least shade tolerant of all trees. It is classed as very  intolerant of shade. The vigor of Digger pine declines rapidly when  competing with such dense-crowned associates as ponderosa pine, blue oak,  California black oak, and the live oaks. The wide spacing of Digger pine  on xeric sites probably stems from root competition for soil moisture,  rather than from mutual competition for light. On mesic sites with better   soil development, the sparse crowns of even-aged Digger pine stands allow  enough light penetration for needles to persist for 3 years, and stand  densities may approach those of moderately-stocked ponderosa pine stands  (25).

    Digger pine's ability to persist and sometimes dominate on xeric sites  on zonal soils probably results from its capacity to photosynthesize  throughout the winter and early spring when soil moisture is abundant, and  to minimize transpiration losses of water during dry seasons through low  foliar biomass and good stomatal action. On zonal soils of more mesic  sites, Digger pine cannot compete with forest vegetation. Where they grow  together in natural ecotones, ponderosa pine has more stomates per needle  than Digger pine and maintains slightly lower leaf water potentials (33).  This, coupled with its greater foliar density, gives ponderosa pine a  growth advantage where soil moisture is adequate. However, Digger pine's  sparse crown (and presumably lower absolute transpiration loss) gives it a  sizable survival advantage where soil moisture is scarce.

    Digger pine's ability to survive and grow slowly even under severe  drought may not be helpful if it is introduced to more mesic sites. During  3 years of normal precipitation at Challenge Experimental Forest, height  growth of planted Digger pine averaged 76 cm (30 in) per year-an average  almost identical to the 74 cm (29 in) for native ponderosa pine (25).  Annual height growth decreased 29 percent in Digger pine during 2 years of  drought, however, compared with a decrease of only 12 percent for  ponderosa pine.

    Digger pine competes well on soils with calcium imbalances. On  serpentinite soils, where calcium availability is low and magnesium  availability high, Digger pine probably owes its success to low nutrient  requirements and preferential absorption of calcium and exclusion of  magnesium. These traits have been identified in some populations of  ponderosa pine (14,24). On limestone soils, where calcium is abundant,  calcium concentrations remain relatively low in Digger pine foliage (34).  Results from such extreme soil conditions suggest that Digger pine is  unusually effective in regulating its calcium supply.

Digger pine produces a deep taproot where soil  depth permits. However, hardpan soils are common along the margins of  California's Great Valley, and this causes trees to have spreading but  shallow root systems with weak taproots extending through duripans. Large  trees growing on such sites are windthrown easily during the winter if  windstorms coincide with waterlogged soil conditions.

More info on this topic.

The seasonal development of gray pine is as follows:

growth starts: March to April [35]
pollination: March to April [15,40]
fertilization: Spring following pollination [40]
cones mature: September to October [40]
seeds dispersed: October to February [40]

Digger pine does not reproduce  vegetatively in nature. No information is currently available on  artificial reproduction.

Seeds of Digger pine show both  physiological and physical barriers to early germination when field  conditions may be unfavorable. Embryos require a moist, near-freezing  chilling period of at least 30 days before germination is possible (9,13).  Digger pine growing on sites where winter temperatures fluctuate greatly,  such as the Modoc Plateau, may have adapted a longer requirement for  chilling to prevent germination until spring. Seeds from populations  growing on low-elevation sites with milder winters tend to require less  chilling, thereby favoring early establishment before soil moisture  becomes limiting (9).

    Digger pine's thick seedcoat provides a formidable obstacle to water  imbibition and gas exchange, and cracking it or reducing its thickness  improves speed and completeness of germination if the chilling requirement  is satisfied (9,13). A further physical barrier is the nucellar cap, and  removing it improves germination more than seedcoat removal alone (9). No  chemical inhibitors of germination in Digger pine seed are known.

    Germination is epigeal (16). Seedlings are established best on bare  mineral soil and under partial (but not deep) shade. Chaparral cover  purportedly helps establishment (29). Cotyledons of Digger pine are  unusually large, averaging 49 to 72 mm (1.9 to 2.8 in) in length, and  seedlings with cotyledons spanning 20 cm (8 in) tip-to-tip have been noted  (6,8). Cotyledon size and number in Digger pine (from 10 to 21 per  seedling) help provide enough energy through photosynthesis so that, where  soil depth permits, first-year seedlings may develop a deep taproot before  soil moisture is depleted in late spring or early summer. Controlled  studies show that most of the first season's growth is completed and bud  differentiation begins within 5 months of germination. First-year foliage  consists mainly of cotyledons and primary needles, although secondary  needles (in fascicles of three) may be produced on better sites toward the  end of the growing season. Although overall growth is depressed on poor  sites, shoot-root ratios tend to be lower as well so that  transpiration-absorption deficits may be balanced to some degree (8).

Compared with other species,  Digger pine is a consistent seed producer, with large crops produced at 2-  to 3-year intervals. Cones may open slowly so that dispersal, beginning in  October, sometimes extends into winter. Although open, cones may contain  moderate numbers of seeds as late as February (6,16,30).

    Digger pine seeds are disseminated in four ways. Wind, usually the  primary distributor of seeds for most species, has less influence on  Digger pine seeds because wings are poorly developed and seeds are heavy.  Birds, primarily the acorn woodpecker and scrub jay, disseminate seed.  Gravity also aids distribution of seeds. Digger pine cones, because of  their shape and weight, may roll considerable distances on steep hillsides  once severed from tree crowns. The large seeds of Digger pine also may  roll when dropped from high in the crown. Finally, Digger pine cones are  relatively buoyant, with specific gravities varying between 0.59 and 0.96  (7). Cones reaching running water may be transported considerable  distances. In one instance, cones were found on a streambank within 13 km  (8 mi) of the ocean, and 40 km (25 mi) downstream from the nearest known  source (30).

Digger pine is monoecious, and strobili  appear on short stalks in early spring. Male strobili are 3 to 4 cm (1.2  to 1.6 in) long, green or yellow to reddish purple when immature and light  brown when mature. Female strobili are initially small and green or red to  purple. When mature they are heavy, ovoid to subglobose, light- to  chocolate-brown woody cones. The cone is borne close to the branch on  reflexed stalks 5 to 6 cm (2 to 2.5 in) long. Pollination occurs in March   through April and archegonia are fertilized in the spring of the next year  (16). Cones mature by September or October. Although cones have been noted  on 2-year-old trees (30), 10 to 25 years usually must pass to attain full  seed production (16). Seeds of Digger pine are large at maturity,  averaging 19 to 25 mm (0.75 to 1.0 in) long (30), and weighing up to 1 g  (0.04 oz) and more when air-dried (6). Embryos average 18 to 35 mg (0.3 to  0.5 gr) (9) and are surrounded by thick seedcoats. Cleaned seeds average  1,280 per kilogram (580/lb) and range between 1,170 and 1,430 seeds per  kilogram (530 and 650/lb). Among the American pines, only Torrey pine (Pinus  torreyana) rivals Digger pine in average seed weight (16).

    One of Digger pine's most prominent features is its massive cones, among  the largest produced by any pine species. Fresh cone weights average 0.3  to 0.7 kg (0.7 to 1.5 lb) and may exceed 1 kg (2.2 lb) (7). Lengths often  reach 20 to 30 cm (8 to 12 in), although mature cones can be much smaller.  Large elongated cones are frequently found in populations of the north  Coast and Klamath Ranges. Smaller ovoid cones are more common in the  Sierra Nevada (7). Prominent features of Digger pine cones are the  conspicuous spurs that develop at the base of the cone. Formed from the  combined umbo and apophysis of the scale, spurs tend to elongate and  recurve, giving the cone a spiny appearance that is fairly constant within  a tree, but quite variable within and between populations (7). Unlike most  other conifers, Digger pine cones do not form an abscission layer of cells  where the cone joins the branch. Thus, cones remain attached long after  seeds are shed, unless broken from the tree crown by wind or cut from the  tree by the western gray squirrel in quest of seed.

Early growth rates of Digger pine are among  the highest of any conifer-an amazing fact, considering the droughty sites  on which the species grows. Annual height growth of Digger pine in its  native range may average as much as 70 cm (28 in) for the first 8 years  after germination (30) and often exceeds 1 m (3 ft) during specific years.  When introduced to Challenge Experimental Forest in northern California, a  very productive Sierra Nevada mixed-conifer site at 790 m (2,590 ft)  elevation, dominant and codominant Digger pine averaged 10.3 m (33.8 ft)  in height and 19.3 cm (7.6 in) in d.b.h. 15 years after planting (25).

    Growth can begin with the first fall rains and continue until soils  become too dry in the spring or early summer (18). Within the natural  range, high annual rates of growth probably reflect a long growing season  that begins early, rather than rapid growth on a daily basis. Digger  pine's sparse foliage suggests that daily rates of growth probably are  low. On more productive timber sites, the growing season may begin later  but extend further into the summer, producing growth rates similar to  those on the best low-elevation sites within its natural range. In one  study, height and diameter growth rates of Digger pine on a high quality  site were comparable, but not superior, to those of native ponderosa pine  (25).

    The stem form of Digger pine seemingly disregards gravity. Even on steep  slopes it may grow nearly perpendicular to the ground. Trees usually  maintain a straight, conical form into the pole stage, but mature trees  generally are twisted and have multiple forks. The poor form of mature  trees probably is a genetic trait but may be traced partly to an  open-grown nature that exposes the trees to the damaging effects of wind  and to the tendency of lateral buds to elongate when the terminal bud  remains static (6). Although Digger pine stands may approach stocking  densities of 46 m² basal area per hectare (200 ft²/acre) (25),  most stands are stocked much more lightly. Mature trees average 12 to 24 m  (40 to 80 ft) in height and 30 to 90 cm (12 to 36 in) in d.b.h. The  largest Digger pine officially recorded measured 48.8 m (160 ft) tall, 160  cm (63 in) in d.b.h., and had a crown spread averaging 20.7 m (68 ft) at  the widest points (22). Size and age potentials are not determined easily  from the trees existing today, because miners, wood cutters, and  agriculturalists cleared Digger pine from its best sites more than a  century ago. The maximum age reached by this species probably exceeds 200  years.

The most obvious variation between Digger pine populations is in cone  shape and size (7). Stands in the north Coast Ranges and Klamath Mountains  tend to bear large, elongated cones, while those in the Sierra Nevada  produce cones that are smaller and ovoid. Variation within a population is  great enough, however, that small or large cone races probably do not  exist. Early claims of a variety explicata (15), based on  strongly-hooked cone spurs and relatively long seed wings, are not  supported by more recent sampling (7). One isolated Klamath Mountain  population, however, tends to have blunt, straight spurs. Cones from the  northern part of Digger pine's range tend to have lower specific gravities  than those from the southern part.

    Seeds collected from sites characterized by cold winters and short  growing seasons show the slowest germination rates and require longer  chilling periods to achieve full germination (6,9), presumably  representing a survival advantage for a species whose seeds normally  germinate during winter. Despite the ability of Digger pine to reproduce  and grow on extremely infertile soils, such as those formed from  serpentinite, no strong evidence has been found that edaphic ecotypes  exist within the species (8). Digger pine is resistant to interspecific  breeding, and no natural hybrids have been recognized although its range  overlaps those of several species of pines. It has been successfully  crossed artificially with Coulter and Torrey pines (2,7,10).

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

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Barcode of Life Data Systems (BOLDS) Stats
Public Records: 4
Specimens with Barcodes: 10
Species With Barcodes: 1

Rounded Global Status Rank: G4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status, and wetland indicator values.

More info for the term: tree

Gray pine is considered an undesirable weed tree by many rangeland
managers. Production and quality of forage growing under gray pine is
less than that growing under blue oak. Additionally, gray pine provides
little shade for livestock during hot summer months [13,22,40]. It has
been extensively cut within the last century in order to clear rangeland
areas [40].

Diseases: Prominent diseases of gray pine include western gall rust
(Periderium harknessii) and dwarf-mistletoe (Arceuthobium occidentale
and A. campylopodum forma campylopodum) [1,20,31,40]. Western gall rust
forms galls on gray pine throughout its range but rarely causes serious
damage. Dwarf-mistletoe is a particularly damaging and widespread
disease [40]. It infects trees of all ages, causing reduced tree vigor
or death. Left uncontrolled, infection can increase sixty-fold within
10 years [20]. Arceuthobium occidentale also infects Douglas-fir
(Pseudotsuga menziezii) and bigcone Douglas-fir, while A. campylopodum
forma campylopodum can infect Coulter, Jeffrey (Pinus jeffreyi),
Monterey (P. radiata), and ponderosa pines [20,31]. Dwarf-mistletoe is
controlled by cutting infected trees or removing infected branches [31].

Gray pine is the specific host for Ips spinifer. This bark beetle
generally attacks fire- or drought-weakened trees. Heavy resin
production by healthy trees provides a strong defense against most
species of bark beetles. Gray pine is host to a variety of cone, twig,
and foliage insects, but the damage they cause is usually minor [40].

Gray pine growing in hardpan is susceptible to windthrow under
waterlogged soil conditions [40].

This species is available from most nurseries within its range that handle native plants. Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”

The Pomo pruned the trees periodically.

More info for the terms: tree, xeric

Gray pine has been planted on a limited basis for erosion control.
Commercial nursery stock is unavailable. Seedlings have been
established on rehabilitation sites by planting 1- or 2-year-old
bareroot stock grown from locally collected seed [27,29]. Gray pine
is an appropriate choice for planting in soils with calcium imbalances.
It will grow well on both serpentine soil, where calcium is deficient,
and on limestone soil, where calcium is abundant. In addition, it will
grow on xeric sites where establishment of other tree species is
difficult [40].

Gray pine wood has minor commercial value. It is used for making
railroad ties, box shook, pallet stock, and chips. Poor form, high
resin content, and high proportions of compression wood result in low
stumpage prices. The mechanical strength properties of the wood have
been detailed [49]. Gray pine is expensive to log due to low stand
density [40].

The blue oak-gray pine community is preferred habitat for black-tailed
deer, California quail, and mourning dove [9]. Gray pine seeds are an
important diet item for various birds and rodents. Scrub jay, acorn
woodpecker, and California gray squirrel are major seed consumers [40].
Livestock also eat the seeds. High concentrations of resins and
terpenes render gray pine browse unpalatable [42].

The percent composition of gray pine seeds is as follows [47]:

protein 25.0
fat 49.4
carbohydrate 17.5
Kcal/100 g 571

The concentrations of several essential minerals in gray pine seeds
are available [47].

Gray pine seeds were important in the diet of California Indians [40].

Seeds of Digger pine have considerable nutritional value. Their protein  and fat contents are similar to those of Pinus pinea (a pine of  the Mediterranean region whose seeds are harvested for the table), and are  equal or superior to those of other commercial species (4). Although  Digger pine seeds are not raised commercially, they once were an important  supplement to the diet of California valley Indians (23,30).

    Digger pine wood has many favorable properties that determine its  special uses. Its 0.43 mean specific gravity almost matches that of  Douglas-fir (Pseudotsuga menziesii), and its strength properties  are comparable with those of ponderosa pine (27). Kraft pulps made from  Digger pine rate high in bursting and tensile strength and compare  favorably with pulps from most northern conifers (19). Poor form, high  resin content, high proportions of compression wood, and low stand  density, however, characterize a species commanding only minor commercial  interest today.

    Currently, the tree's primary value is as a source of railroad tie  material, with secondary values for box shook, pallet stock, and chips  (17). Digger pine is expensive to log because of its low stand density,  and to transport because of its heavy weight and often crooked form.  Consequently, stumpage prices are low (17). One of Digger pine's few  commercial advantages is that foothill stands can be logged during winter,  when species at higher elevations often are inaccessible. Also, some  potential exists as stock for shelterbelt plantings on and sites (29).

    Normal heptane, an alkane hydrocarbon of rare occurrence in woody  tissues, is the principal constituent of Digger pine wood turpentine and  constitutes about 3 percent of needle and twig oil (20).

Ethnobotanic: The seeds of gray pine were eaten by many California Indian tribes and are still served in Native American homes today. They can be eaten fresh and whole in the raw state, roasted, or pounded into flour and mixed with other types of seeds. The seeds were eaten by the Pomo, Sierra Miwok, Western Mono, Wappo, Salinan, Southern Maidu, Lassik, Costanoan, and Kato, among others. Sierra Miwok men climbed the trees and twisted the green cones off by hand before the seeds were fully developed. These immature cones were roasted for 20 minutes in hot ashes, yielding a brown, sweet syrup. The pitch of the gray pine was used as a medicine by the Western Mono and the branches were made into household utensils for stirring acorn mush. The Costanoan used the pitch as a treatment for rheumatism. The needles were used for thatch, bedding, and floor covering and the bark for house covering by the Sierra Miwok. The branches and roots were used in California Indian basketry and still gathered to a limited extent by contemporary weavers.

Wildlife: Numerous birds feed on the seeds of gray pine including the red-shafted flicker, California jay, and band-tailed pigeon. The foliage, bark, and seeds provide food for black bears, Douglas chickarees, and

gray squirrels. Mule and white-tailed deer browse the foliage and twigs.

Seeds of Pinus sabiniana were an important food source for many Indian groups in California, sometimes collectively referred to as "Digger Indians." Because the name "Digger" has been used as a derogatory ethnic term, many people prefer to avoid using the vernacular name Digger pine.