Mean Pacific dogwood cover values (n = 3),
in year 10 (n = 2)
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available [60,63,64,67,91,98].
Pacific dogwood is a native, deciduous, multi-branched tree, sometimes considered a shrub. Average mature-height estimates range from 20 to 75 feet (6.1-22.9 m) and canopy spread is often 20 feet (6.1 m) [60,64,76,83,85,104]. Young bark is thin and smooth, but ridges develop later making the trunk appear scale like [23,98]. The maximum trunk diameter reported for Pacific dogwood was 24 inches (61cm) [67]. The root system, commonly a taproot, penetrates deeply [67].
The growth form of Pacific dogwood may change with site conditions. When grown under a canopy of vegetation, the trunk is normally tapered and the crown is slender and short. When developed under a sparse canopy or in the open, the trunk is typically shorter, and the rounded crown can be as wide as it is tall [67]. Pacific dogwood branches have fine hairs and bear simple, opposite leaves that measure between 2 and 5 inches (5.1-12.7 cm) long by 1.5 to 2.8 inches (3.8-7.1cm) wide [11,60,64,67,91,98]. Leaves are hairier on the underside but have stiff appressed hairs above [60,91]. Pacific dogwood bears 2-seeded drupe fruits that are 1 to 1.5 cm long [63,64,91,98]. Commonly each drupe is comprised of 20-40 drupelets that are slightly flattened from being held in a tight cluster; contained seeds are smooth [67,91].
As a subcanopy species, Pacific dogwood has several shade growing adaptations. At 1/3 full sunlight, Pacific dogwood maintains maximum photosynthetic potential [11]. Branches are self-shading; leaf petioles orient downward allowing leaves to rest on and shade the branches. Although the trunk of Pacific dogwood can be damaged by direct sunlight [84,104], established plants may initiate shoot growth from the crown to shade and protect the exposed trunk [104].
Although typically considered a mesic species, Pacific dogwood is quite drought tolerant. The osmotic potential at zero turgor is -2.2 MPa; leaves begin to lose turgor pressure at 16-18% relative water deficit [108].
Botanical characteristics are altered when plants are infected with dogwood anthracnose, a nonnative fungal disease caused by Discula spp., common in Pacific dogwood [22,24,30,31,32]. Fungal activity is usually greatest from May through early July. However, the fungus can be active any time conditions are moist and plants are growing [24]. Infected leaves develop blotches and often drop early. Defoliation can be extreme. Twigs with this fungal disease are depressed in spots and allow the fungus to progress into leaf buds, killing them and setting back spring emergence [32]. Seed production diminishes with anthracnose infection [38]. This fungal disease is considered threatening to native Pacific dogwood populations because of its rapid spread and severe effects [25]. Control measures have been described by many [24,30,31,32].
Pacific dogwood occupies a discontinuous range. It occurs in the coastal regions west of the Cascade Mountains from southern British Columbia to southern California [39,64,91]. Only occasionally are Pacific dogwood populations found in the mountains of San Diego and Los Angeles counties of California [91]. There is a disjunct population of Pacific dogwood in northern Idaho along the lower Lochsa and Selway rivers [8,38,39,82]. The Idaho population is considered threatened [38,68,69,90].
The Flora of North America provides a distributional map of Pacific dogwood.
Fire adaptations: Pacific dogwood sprouts following fire [105]. Root crown sprouting and/or epicormic branching can occur following fire [1,19].
FIRE REGIMES: The fire regime for Pacific dogwood is dependent on the overstory community, site conditions, and historical disturbances. In the central and south Sierra Nevada, indigenous people historically burned areas to encourage new growth in Cornus spp. Fires were set in the fall and burning occurred at 1- to 2-year intervals [5]. Others also suggest that fires were common in the Sierra Nevada. Parsons and DeBenedetti [95] suggest that fires frequently burned in sequoia and mixed conifer forest types. The poor recruitment of giant sequoia is thought to be related to fire suppression efforts in these areas [95,129]. Fires were also frequent in the Siskiyou region of California and Oregon; fire severities however ranged widely [133].
In the Klamath Mountains of California, researchers investigated 75 plots in 3,880 acres (1,570 ha) to reconstruct the fire history. They estimated the average area burned was 865 acres (350 ha) with 16 fires between 1627 and 1992 that were greater than 1,236 acres (500 ha). Most fires were of low and moderate severities, although stand-replacing fires also occurred. Estimated average fire return intervals are shown below [124].
Presettlement (1626-1849) 14.5 years Settlement (1850-1904) 12.5 years Suppression (1905-1992) 21.8 years
In the Lochsa-Selway area of Idaho, Roper [105] reports that large fires burned in 1910, 1919, 1924, 1930, 1934 and smaller fires occurred in 1949-50 and 1967. Heavy moisture in the winter and spring months allows fuels to accumulate in this area, while hot, dry summers foster burning conditions. Climate regime is likely the primary driving factor of frequent fires in this area [105].
Not all areas where Pacific dogwood is common burned often. Riparian areas often burn less frequently and/or burn at lower severity than the surrounding slopes [1]. In coastal redwood forests of northern California, lightning caused fires were infrequent. In this high humidity region, the author estimates from age class and fire scar distributions that low-severity fires occurred at 250- to 500-year intervals on mesic sites, at 50-year intervals on xeric sites, and at 100- and 200-year intervals on intermediate sites [130].
The following table provides fire return intervals for plant communities and ecosystems where Pacific dogwood is important. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Community or Ecosystem Dominant Species Fire Return Interval Range (years) silver fir-Douglas-fir Abies amabilis-Pseudotsuga menziesii var. menziesii > 200 grand fir Abies grandis 35-200 Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to > 200 Jeffrey pine Pinus jeffreyi 5-30 western white pine* Pinus monticola 50-200 Pacific ponderosa pine* Pinus ponderosa var. ponderosa 1-47 [9] interior ponderosa pine* Pinus ponderosa var. scopulorum 2-30 [9,14,80] Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [9,10,12] coastal Douglas-fir* Pseudotsuga menziesii var. menziesii 40-240 [9,89,103] California mixed evergreen Pseudotsuga menziesii var. menziesii-Lithocarpus densiflorus-Arbutus menziesii < 35 California oakwoods Quercus spp. 9] coast live oak Quercus agrifolia 2-75 [48] canyon live oak Quercus chrysolepis <35 to 200 Oregon white oak Quercus garryana 9] California black oak Quercus kelloggii 5-30 [97] redwood Sequoia sempervirens 5-200 [9,41,122] western redcedar-western hemlock Thuja plicata-Tsuga heterophylla > 200 western hemlock-Sitka spruce Tsuga heterophylla-Picea sitchensis > 200 mountain hemlock* Tsuga mertensiana 35 to > 200 [9] *fire return interval varies widely; trends in variation are noted in the species reviewFire management considerations often involve more than just the postfire community or species response. Following an early spring fire in giant sequoia forests of Tulare County, California, Lawrence and Biswell [81] found that the utilization of Pacific dogwood by mule deer was significantly greater (p<0.01) on logged and burned sites. The authors note that the "resulting crown sprouts were browsed so heavily that the survival of such trees seemed doubtful."
When setting prescription fires in giant sequoia groves, the California Parks and Recreation Department 1st raked around Pacific dogwood as they considered this species prone to cambium damage and wanted to reduce the "visual and environmental" impacts of the fire [57].
Pacific dogwood's low frost tolerance, high flood tolerance, and moderate shade tolerance make it common along stream banks and in low-elevation coniferous, hardwood, and mixed coastal forests with temperate to mesothermal climates [64,67,78,98]. Brush [23] considers Pacific dogwood populations best developed in Douglas-fir forests of the Puget Sound Basin and redwood forests of California. Typical habitat for Pacific dogwood includes sites with moist but well-drained soils, on gentle slopes, predominantly occurring below 5,000 feet (1,524 m) in elevation [23,98].
Climate: The climates in Pacific dogwood's range are mild and moist. Mediterranean-marine and temperate maritime weather patterns are typical [44,113,130]. Average annual precipitation ranges from a low of 12.2 inches (310 mm) in the Siskiyou Mountains of Oregon and California to a high of 100.4 inches (2,550 mm) in western Washington [17,133]. The majority of precipitation falls between late fall and early spring as rain and/or snow depending on the elevation of the site. During the growing season in parts of Washington, precipitation levels are less than 10% to 25% of the annual average [17,43]. Low winter temperatures range from 30.2°F (-1 °C) to 50 °F (10°C) reported for the Sierra Nevada and coasts of Oregon and California, respectively [16,107]. Maximum summer temperatures range from 60 to 72.7 °F (15.6-22.6 °C) reported for the coasts and Siskiyou Mountains of Oregon and California, respectively [107,133]. In Idaho, Pacific dogwood's restricted range is driven by climatic factors. The Lochsa-Selway region of Idaho receives high levels of winter and spring precipitation while summers can be hot and dry; annual precipitation in this area averages 34 inches (864 mm). Winter low temperatures average 29.5 °F (-1.4 °C) to 31.6 °F (-0.2 °C) and summer highs average 70 to 72°F (21-22.2 °C) [105].
Soils: The soils described in association with Pacific dogwood habitat are typically deep (often ≥ 6.6 feet (2 m)), moist, and well-drained [4,23,43,85,104]. Soil textures can range from clay to sand loam types [4,8,43]. Pacific dogwood soils often are high in humus content and have a low pH (5.5-6) [8]. The permeability of most Pacific dogwood soils is slow and the water holding capacity is high (59.1 to 98.4 inches (150-250 cm)) [4]. Moderate to high levels of calcium, magnesium, nitrates, potassium, and phosphorus are also typical of soils supporting Pacific dogwood [78].
While a majority of soils associated with Pacific dogwood are deep, in a study of early succession of the mud flows that followed the Mt. St. Helens volcanic eruption, Pacific dogwood was only found on nonorganic substrates with less than 9.8 inches (24.9 cm) of buried soil. Frequency of Pacific dogwood on this site was less than 1% [53].
Elevation:
California Sierra Nevada Range: below 1,500 feet (547 m) [16]Utilization of Pacific dogwood by large mammals and livestock is related to time since last disturbance, as new sprouts are browsed more heavily than mature vegetation.
Domestic livestock: The quality of mature Pacific dogwood browse is considered fair to poor for domestic sheep and goats and is thought to be "worthless" browse for horses and cattle. New sprouts however are preferred by livestock [111]. Pacific dogwood was heavily grazed by domestic sheep in areas of the Columbia National Forest that had burned 4 to 8 years earlier [70].
Wildlife: Large mammals: In the summer, grazing by mule deer was greater than 50% (significantly greater (p<0.01)) for 3 sampling seasons following logging and burning [81]. Pacific dogwood sprouts resulting from a clearcut were utilized by deer. Sixty-two percent of sprouting clumps were browsed; 10% were considered heavily browsed [106]. Researchers found Pacific dogwood in 33% of the 69 elk stomachs collected from January through March near the Lochsa and Selway rivers of northern Idaho. However, Pacific dogwood browse made up just 3% of their total diet [127]. On a 40-year-old burn, black-tailed deer very rarely browsed Pacific dogwood even though food was scarce due to high deer populations (>100 deer/mi2) [61]. When browsing was monitored in enclosed Douglas-fir plantations burned 21-22 years ago, the high density black-tailed deer population (126 deer/mi2) did not feed on Cornus spp. during winter months [62].
Small mammals: Few studies have focused on small mammal use of Pacific dogwood. During the fall months in Plumas County, California, Pacific dogwood fruits were eaten and 1 end of the seeds was gnawed, likely by deer mice [71]. Gilbert and Allwine [47] report finding the red tree vole often with medium-sized Pacific dogwood and other berry producing shrubs. While this finding may be related to food preferences of this species, the authors caution that this finding may be the result of a small sample size.
Birds: Pacific dogwood fruits are attractive to many birds [11]. Band-tailed pigeons and pileated woodpeckers feed on Pacific dogwood fruits [11,87,98]
Palatability/nutritional value: Palatability of Pacific dogwood is associated with age of the plant tissue. Palatability is considered low for mature Cornus spp. due to bitter cell sap [111]. For slugs, the palatability of Pacific dogwood is considered average [27]. In a recently burned area however, Pacific dogwood is considered palatable [70]. Roper [105] claims that palatability of Pacific dogwood is highest for 2 or 3 years following fire.
Several nutrient and structural components of Pacific dogwood have been described. Pacific dogwood had the highest calcium levels of the 5 conifer, 4 shrub, and 2 broadleaf forest species analyzed in a giant sequoia forest community. Other nutrient levels reported were: 9% protein, 3.1%-2.7% fat, and 12.2%-13.6% fiber. Interestingly, calcium and fiber levels were slightly higher on logged and burned sites [81]. There are also high levels of aluminum in the leaves and branchlets of Pacific dogwood [102]. The average lignin and nitrogen content of leaves collected in Oregon was 6.2% and 0.87%, respectively [132].
Cover value: Few studies have investigated the value of Pacific dogwood as habitat or cover. It is probable though that this species provides cover and habitat to some birds and small mammals. Pacific dogwood can grow as a large shrub or tree and likely these different forms provide cover or habitat for different animal species. Sampson [111] considers Cornus spp. important shade providers to larger ungulate species. Wilson's warbler is attracted to meadows surrounded by Cornus spp. [119].
British Columbia:
Pacific dogwood is common in Douglas-fir (Pseudotsuga menziesii) and western
hemlock (Tsuga heterophylla) forests of southwestern British Columbia [78].
Washington:
Cascade Range: In Douglas-fir-western hemlock-Pacific
silver fir (Abies amabilis) mixed forests, pacific dogwood is a common subcanopy
species. Other canopy vegetation can include grand fir (A. grandis), noble fir
(A. procera), Pacific yew (Taxus brevifolia), western redcedar
(Thuja plicata), and bigleaf maple (Acer macrophyllum). Associated shrub
species are vine maple (A. circinatum), Oregon-grape (Mahonia repens),
salal (Gaultheria shallon), red huckleberry (Vaccinium parvifolium), and
Pacific rhododendron (Rhododendron macrophyllum) [17,29,43]. In Mount Rainier
National Park, Pacific dogwood occurs in western hemlock/sweet after death (Achlys triphylla)
and western hemlock/salal vegetation associations [44].
Oregon:
Cascade Range:
In the west-central Cascades, Pacific dogwood occurs in old-growth Douglas-fir forests.
Pacific dogwood coverage is greatest in Douglas-fir/Pacific rhododendron communities that
occupy warm, mesic, south slopes. Coverage of Pacific dogwood is less in Douglas-fir/giant
chinquapin (Chrysolepis chrysophylla) and Douglas-fir/Pacific rhododendron/Cascade
barberry (M. nervosa) communities that are found on xeric south slopes and on mesic sites,
respectively [49]. Pacific dogwood is also typical in Douglas-fir/vine maple/western sword fern
(Polystichum munitum), western hemlock/vine maple/western sword fern, and western
hemlock/salal communities
[110].
Coast Range:
Along the east slope of the Coast Range, Pacific dogwood occurs in both the vine maple/salal
and oceanspray (Holodiscus discolor)/salal community types. Coverage is normally
greater in the oceanspray/salal community [3]. In the Douglas-fir forests of the southern
Coast Range, Pacific dogwood is commonly associated with California bay (Umbellularia
californica), tanoak (Lithocarpus densiflora), and evergreen huckleberry
(V. ovatum) [26]. On the eastern side of the Coast Range, Pacific dogwood in typically
found with Douglas-fir, western redcedar, bigleaf maple, Oregon ash (Fraxinus latifolia),
and bitter cherry (Prunus emarginata) [28,50].
Siskiyou Region:
Pacific dogwood is common in tanoak-California bay/Pacific rhododendron and tanoak-redwood
(Sequoia sempervirens) vegetation types of southwestern Oregon [13].
Willamette Valley:
At low elevations in the Willamette Valley, Pacific dogwood occurs in Oregon white oak
(Quercus garryana) forests. Other associated vegetation includes, California black oak
(Q. kelloggii), canyon live oak (Q. chrysolepis), bigleaf maple, Oregon ash,
ponderosa pine (Pinus ponderosa), incense-cedar (Calocedrus decurrens), Pacific
madrone (Arbutus menziesii), and tanoak [120,125].
Oregon/California:
Coast Range:
In the Douglas-fir-tanoak-Pacific madrone cover type, Pacific dogwood is found with salal,
evergreen huckleberry, Oregon-grape, Pacific rhododendron, and poison-oak
(Toxicodendron diversilobum) [113]. In redwood forests of Oregon and California,
Douglas-fir, western hemlock, tanoak, California hazel, salal, Pacific ninebark
(Physocarpus capitatus), and Pacific rhododendron commonly occur with Pacific dogwood [107].
Klamath Range:
Within the Pacific ponderosa pine (Pinus ponderosa var. ponderosa)
-Douglas-fir forest type of the Klamath Mountains, Pacific dogwood is common [86].
Pacific dogwood is also in the understory of white fir (Abies concolor)/dwarf Oregon-grape
and mixed evergreen forests. More unique species in these forests include, sugar pine
(P. lambertiana), Port-Orford-cedar (Chamaecyparis lawsoniana),
and California hazel (Corylus cornuta var. californica) [114,134].
California:
Coast Range:
Pacific dogwood is common in Douglas-fir-hardwood and ponderosa pine forests
of the California Coast Range [18,20,115]. In ponderosa pine forests, typical overstory species
are sugar pine, Douglas-fir, gray pine (P. sabiniana), white fir, incense cedar,
and Oregon white oak. Understory associates include manzanitas (Arctostaphylos spp.),
deerbrush (Ceanothus integerrimus), California coffeeberry (Rhamnus californica),
birchleaf mountain-mahogany (Cercocarpus betuloides), common snowberry
(Symphoricarpos albus), and poison-oak [18,20].
Sierra Nevada Range:
In the Sierra Nevada Range, Pacific dogwood is common in ponderosa pine/mixed
conifer forests that include tanoak, California black oak, Sierra mountain misery
(Chamaebatia foliolosa), and poison-oak [4]. Pacific dogwood is also typical
of forests described as Sierra Nevada-Sierran montane and Sierra Nevada mixed
conifer types [7,16,123]. In giant sequoia (Sequoiadendron giganteum) forests,
Pacific dogwood, canyon live oak, Scouler willow (Salix scouleriana), white
alder (Alnus rhombifolia), California hazel, whiteleaf manzanita
(Arctostaphylos viscida), Sierra Mountain misery, California wildrose
(Rosa californica), and Sierra gooseberry (Ribes roezlii)
make up the understory vegetation [75,109].
Idaho:
Pacific dogwood in the Lochsa-Selway area of northern Idaho is found in the western red
cedar-western hemlock vegetation zone [105]. Hickey [59] reports that Pacific dogwood is
also associated with Douglas-fir, grand fir, bitter cherry, oceanspray, Saskatoon serviceberry
(Amelanchier alnifolia), common snowberry, Scouler willow, thimbleberry
(Rubus parviflorus), Rocky Mountain maple (Acer glabrum) and red-osier dogwood
(Cornus sericea).
Showy flowers and brilliant fall colors make Pacific dogwood a valuable ornamental species [104,112].
Pacific dogwood bark was used by Nlaka `pamux, indigenous people of the Pacific Northwest Coast, to make brown dye. Bark has also been prepared and used as a blood purifier, lung strengthener, and stomach treatment [98]. Arno [11] suggests that historically the bark of Cornus spp. was used to cure malaria and when boiled had laxative properties.
Wood Products: The wood of Pacific dogwood has several uses. This hardwood species has been used to make bows, arrows, thread spindles, cabinets, piano keys, mallet handles, golf club heads and other tools [2,11,23,67,98]. Young shoots of Cornus spp. were used by indigenous people of central and south Sierra Nevada for basket making [5]. The collection of Pacific dogwood is currently prohibited in British Columbia [98].
The wood of Pacific dogwood is hard, heavy, has a whitish color, a fine grain, and wears smoothly [67,93]. For more about wood properties see [2,23,93,96] and for treatment of the wood see [2,93].
Pacific dogwood reproduces both sexually and asexually. Regeneration occurs through seed production and/or by vegetative sprouting [3,82,104,105].
Breeding system: Outcrossing is likely common in Pacific dogwood as pollination is insect mediated [6]. Autogamy was not discussed in the literature.
Pollination: Pacific dogwood flowers are chiefly pollinated by insects [6].
Seed production: Reports of seed production by Pacific dogwood vary considerably. Lichthardt [82] suggests Pacific dogwood inflorescences produce 20 to 60 head flowers, each of which produces a single seed, but others consider Pacific dogwood drupes to be 2-seeded [63,64]. Brush [23] claims that Pacific dogwood produces abundant seed annually. Brinkman and Vankus [21], in a review, report that there are usually 2 years between large seed crops produced by Pacific dogwood. Following monitoring in Idaho, researchers found Pacific dogwood produced a significant amount of seed in only 1 year out of 5 [82]. Roper [105] reports that Pacific dogwood reproduces by seed only when growing under canopy cover.
It is likely that seed production is linked to plant maturity. Only larger trees produced seed in Idaho [82]. Roof [104] suggests that Pacific dogwood flowers first when approximately 6 years old. Others report that the minimum seed-bearing age of Pacific dogwood is 10 years [21].
Seed dispersal: The fleshy fruit surrounding Pacific dogwood seeds is likely attractive to bird and small mammal seed dispersers, but seed dispersal was not directly discussed in the literature cited as of this writing (2005).
Seed banking: Pacific dogwood likely banks some seed. In a seed production and seed bank study along 3rd and 5th order streams, Pacific dogwood coverage was recorded only in old-growth Douglas-fir sites on the 5th order stream, but 1 Pacific dogwood seed germinated in soil collected along the 3rd order stream [54].
Germination: Germination of Pacific dogwood seed under controlled conditions is high. When seed collected from Idaho populations was sent to horticulturalists, they reported a 63% germination rate [82]. In a review, Brinkman and Vankus [21] report that germination averaged 81% when tested on sand and wet paper.
Seedling establishment/growth: While shading seems important to seedling emergence, deep shade may not provide for establishment, growth, and reproduction of Pacific dogwood. Brush [23] reported that the highest number of seedlings grew in deep shade or on moist streambanks. Likewise, Roper [105] chiefly observed seedlings on sites with greater than 46% canopy cover. Successful seedling establishment in Idaho occurred on sites with 45%-60% canopy cover [105]. However more recently in Idaho, researchers could not find Pacific dogwood populations considered large enough for monitoring purposes in understory sites. Large populations of Pacific dogwood were associated with shrub-dominated areas. A single monitoring plot was located on a deep shade site, but plants had not recruited vegetatively or by seed in 5 years of monitoring [82].
Asexual regeneration: Pacific dogwood readily sprouts following disturbance. In Idaho, sprouting has been the only regeneration in several years, as no seedlings were located in monitoring sites [82]. Two years following a clearcut operation in northwestern California, Pacific dogwood averaged 19 sprouts per stump. Sprouts reached a maximum of 4.2 feet (1.3 m) tall and clumps of sprouts were a maximum of 4.5 feet (1.4 m) in diameter [106]. Layering was also observed in newly sprouting Pacific dogwood plants [105].
Pacific dogwood can tolerate early-, mid-, and late-seral conditions. In a study of herbivore successional preferences, researchers considered the presence of Pacific dogwood an indication of early-seral perennial vegetation based on reviewed literature and peak population occurrences [27]. However, in a study of water-formed terraces, floodplains, and glacial outwash plains along the McKenzie River Valley in Oregon, Pacific dogwood was present only in what the author considered late seral (100- to 200-year-old) and climax (200- to 500-year-old) communities [58]. Whittaker [134] considers Pacific dogwood part of the climax mixed evergreen vegetation in the Klamath region.
In Idaho, Pacific dogwood was present in all stages of succession. Its prolific sprouting following the removal of above ground biomass is considered important in the recolonization of sites with pioneer conditions. Below are the average percent coverages of Pacific dogwood in order of advancing successional communities on western redcedar-western hemlock forest sites. In those communities for which a range of coverages is given, the range is representative of the average percent cover reported for multiple sites within the seral community [105].
Seral community Immature shrub Mature shrub Mature shrub-young conifer Shrub-Betula (birch) Seral conifer Climax conifer Pacific dogwood cover (%) 8-19 <1-5 31-48 9-21 16-88 3-7
When studies compared disturbed and undisturbed sites, Pacific dogwood was commonly present in both. Following a clearcut of 125-year-old Douglas-fir stands, Pacific dogwood was present the 3rd postlogging year [66]. Likewise, 5 years after Douglas-fir forests of northwestern California were logged Pacific dogwood coverage was 11%. In unlogged "virgin" forests, coverage of Pacific dogwood was 9% [51]. Pacific dogwood has even been considered an "invader" by some. In clearcut, old-growth Douglas-fir forests of the Cascade Range, Pacific dogwood was considered an invader because it was not found in the understory of adjacent areas. However, species frequencies were not measured prior to logging, making the absence of Pacific dogwood prior to logging an assumption [135].
In the Cascade Range of Oregon and Washington and in the Coast Range of Oregon, different-aged stands of Douglas-fir resulting from past fires were compared. The basal area of Pacific dogwood trees with greater than 2 inches (5 cm) d.b.h. was measured in young (< 80 years), mature (80-195 years), and old-growth (≥ 195 years) Douglas-fir forests. This study revealed no clear successional pattern for Pacific dogwood. The results are presented below [118]:
Cascade Range, WA Cascade Range, OR Coast Range, OR Young <0.1 m2/ha 0.3 m2/ha 0.2 m2/ha Mature 0.2 m2/ha 0.1 m2/ha 0.1 m2/ha Old growth <0.1 m2/ha 0.1 m2/ha 0.4 m2/ha
The scientific name of Pacific dogwood is Cornus nuttallii Audubon ex.
Torr. and Gray (Cornaceae) [60,63,64,72].
Pacific dogwood, C. florida, and C. kousa are sexually compatible.
These hybrids are commercially recognized [112]:
C. nuttallii ÃÂ florida
(C. florida ÃÂ C. kousa) ÃÂ C. nuttallii
When literature is cited in this review that refers to the Cornus genus
only, it will be indicated as Cornus spp.
Pacific dogwood is easily grown from seed and various seed treatments have been described to artificially overcome dormancy [35,56,84]. Seed collected in the fall can be sown directly into mineral soil to attain the long cool stratification required to overcome seed dormancy. Seed collected in the summer can be dried and refrigerated until fall [56]. Others have soaked seed in concentrated sulfuric acid to overcome seed dormancy [35,84].
The use of Pacific dogwood in revegetation efforts has appealed to many. Evaluations of the revegetation potential of Pacific dogwood have been undertaken as well [34,99].
There are other aspects of Pacific dogwood biology that may affect its use in rehabilitation or revegetation efforts. Pacific dogwood leaves decay rapidly [55,132]. Decay rates for Pacific dogwood were faster than any of the other 6 species tested. Tinnin and Kirkpatrick [126] assessed the growth suppression potential of Pacific dogwood. In a greenhouse study, they found radicle growth to be 38% of normal when cucumber seed was grown on sponges soaked with water leachates of Pacific dogwood leaf litter. The use of cucumber seed in this study makes it difficult at best to make any inferences regarding Pacific dogwood's ability to suppress any native or naturally occurring plant neighbors.
Cornus nuttallii, the Pacific dogwood,[1][2] western dogwood,[3] or mountain dogwood,[2] is a species of dogwood tree native to western North America.
It is a small to medium-sized deciduous tree, reaching 6–23 metres (20–75 feet) tall, often with a canopy spread of 6 m (20 ft). Its habit varies based on the level of sunlight; in full sun it will have a short trunk with a crown as wide as it is tall, while under a canopy it will have a tapered trunk with a short, slender crown.[4] The trunk attains 15–30 centimetres (6–12 in) in diameter. The bark is reddish brown.[5]
The branches have fine hairs and the young bark is thin and smooth, becoming scale-like with ridges as it ages.[4]
The leaves are opposite, simple, oval, 5–13 cm (2–5 in) long, and 3.8–7.1 cm (1+1⁄2–3 in) broad. They are green with stiff, appressed hairs on top, and hairier and lighter on the bottom.[4][5] They turn orange to purplish in autumn.[5]
The flowers are individually small and inconspicuous, 2–3 millimetres (1⁄16–1⁄8 in) across, produced in a dense, rounded, greenish-white flower head 2 cm (3⁄4 in) in diameter; the 4–8 large white 'petals' are actually bracts, each bract 4–7 cm (1+1⁄2–2+3⁄4 in) long and broad, creating the appearance of a larger flower head. The flowers commonly bloom twice per season, once in the spring and again in late summer or early fall.[4][3]
The fruit is a compound pink-red or orange drupe about 1–1.5 cm (1⁄2–1⁄2 in) long, in clusters containing 20–40 drupelets, each of which contains two seeds. They appear in September or October.[3][4]
The eastern United States' Cornus florida (flowering dogwood) is similar in appearance and possibly in chemical composition. Cornus canadensis has similar blossoms but grows as a groundcover.[5]
In 1806, Meriwether Lewis noted that the species is similar in appearance to C. florida.[5] However, when Scottish botanist David Douglas encountered C. nuttalli on his expedition to the Pacific Northwest in the 1820s, he mistook it for C. florida and did not send seeds back to England.[3]
English botanist Thomas Nuttall was the first to describe the species for science while staying at Fort Vancouver in the autumn of 1834.[6] It was named nuttallii after him by his friend John James Audubon.[3]
The common names comes from that of Cornus sanguinea, the hard wood of which Northern Europeans used to make nails ("dags") during the medieval era.[5]
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It occurs from the lowlands of southern British Columbia to the mountains of southern California. There exists an inland population in central Idaho, where it is considered critically imperiled. It occurs predominantly below 1,500 m (4,900 ft) in elevation.[4]
Cultivated examples are found as far north as Haida Gwaii.
It has high flood tolerance, and is common along streams with moist but well-drained soils, often on gentle slopes. Soil composition can range from clay to sandy loam, and it prefers a high humus content, moderate to high nutrient levels, and acidic soils with a pH from 5.5 to 6. It has low frost tolerance, and is usually found in low-elevation temperate or mesothermal climates.[4] It is hardy to USDA zone 7.[3]
New sprouts are good browse for both wild and domesticated ungulates, especially after a recent fire, but the mature foliage is usually ignored by all species except slugs.[4]
The fruit are eaten by deer mice, pileated woodpeckers, the band-tailed pigeon,[4][7] and bears.[5]
It provides habitat and cover to small birds such as Wilson's warbler, and small mammals including the red tree vole.[4]
Like the related Cornus florida, it is very susceptible to dogwood anthracnose, a disease caused by the fungus Discula destructiva. Fungal activity is greatest from May to July, although it can be active any time conditions are moist and the plant is growing. Infected leaves become blotched and drop, and defoliation can be extreme. Twigs and leaf buds are also impacted. This has killed many of the larger plants in the wild and has also restricted its use as an ornamental tree, to the point where it is considered threatening to the species in its native range.[4]
It is present in all stages of both primary and secondary succession – from new colonization on glacial outwash or areas destroyed by the 1980 eruption of Mount St. Helens, to late seral and even climax communities.[4] It is shade tolerant but prefers sunlight in sufficiently humid conditions.[5]
It is adapted to a wide variety of fire regimes, with intervals ranging from just one year on dry sites, to 500 years or more in moist, riparian zones. The tree can survive low severity wildfires which are not hot enough to kill buds protected by bark. After being severely burned, Cornus nuttali typically resprouts from the root crown – however, the resulting shoots are so palatable to mule deer that they are at risk of being killed by over-browsing.[4]
Some Plateau Indian tribes such as the Nlaka'pamux used the bark as a brown dye. Those groups also used the bark for medicinal purposes as a blood purifier, lung strengthener, stomach treatment, laxative, and emetic.[4][8]
The berries are edible by humans, though not very palatable.
It is mostly prized as a cultivated ornamental.[5]
It has been the provincial flower of British Columbia[9] since 1956.[10] It was once protected by law in the province (in an act which also protected Rhododendron macrophyllum and Trillium ovatum),[11] but this was repealed in 2002.[12]
Cornus nuttallii, the Pacific dogwood, western dogwood, or mountain dogwood, is a species of dogwood tree native to western North America.
