John C. Zasada and Howard M. Phipps
Balsam poplar (Populus balsamifera) is the northernmost American hardwood. It grows transcontinentally on upland and flood plain sites but attains the best development on flood plains. It is a hardy, fast-growing tree which is generally short lived, with some trees reaching 200 years. Other names are balm-of-gilead, bam, tacamahac, cottonwood, or heartleaf balsam poplar. Many kinds of animals use the twigs for food. The light, soft wood is used for pulp and construction.
Regularity: Regularly occurring
Regularity: Regularly occurring
Regularity: Regularly occurring
Regularity: Regularly occurring
Global Range: Newfoundland, Labrador to northwest Alaska, northeastern British Columbia, east through Alberta, northern portions of the Great Lakes states, northern New England, and locally from Iowa to Connecticut and in the Rocky Mountains. (Fowells 1965)
Occurrence in North America
MA MI MN MT NE NH NJ NY ND OH
OR PA RI SD TN UT VT VA WV WI
WY AB BC LB MB NB NF NT NS ON
PE PQ SK YT
Balsam poplar occurs mainly in riparian areas of boreal and montane
conifer forests . Its distribution extends from Alaska across most
of Canada to Labrador and Newfoundland [93,101]. In British Columbia it
is restricted to areas east of the Rocky Mountains [8,36]. Balsam
poplar is rare in the northwestern United States, with sketchy records
of its existence in Idaho and Oregon . It occurs sparingly in the
Rocky Mountains of Montana, Wyoming, Utah, and Colorado
[25,26,27,35,36,37,105,106] and extends east through the northern Great
Plains to the Atlantic Coast. It is found along creekbanks, moist
hillsides, sandhill potholes, and knolls in North and South Dakota .
North and east of the Great Plains, balsam poplar forms extensive
floodplain forests . New York  and West Virginia [61,101] are
alternately reported as the southern extreme for this tree in the
eastern United States.
Regional Distribution in the Western United States
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):
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands
-The native range of balsam poplar.
Balsam poplar is a medium to large native deciduous tree. Heights of
mature trees range from 30 to 100 feet (9-30 m) and trunk diameters from
4 inches to 2 feet (10-60 cm) . The trunk of balsam poplar is
straight and cylindrical with an open crown of a few stout ascending
branches . The bark is smooth and light gray to grayish brown but
furrows with age .
Winter buds are 1 inch long (2.5 cm) with sticky resin and a pungent
balsam odor in the spring . Drooping pistillate and staminate
catkins occur on separate trees. Leaves are ovate or broadly
lanceolate, 2.25 to 4.5 inches long (6-11 cm) and 1.5 to 3 inches wide
(4-7.5 cm) . Leaves are shiny green above and pale green below
with finely toothed margins .
Roots are shallow, especially on wet soil types or shallow permafrost
Comments: Climatic conditions vary throughout the ranges, but are often characterized by low seasonal temperature provided by high altitudes or northern latitudes, and short growing seasons. P. balsamifera most frequently grows in moist soils of various textures including subirrigated sandy and gravelly soils, calcareous clay loams, or silt loams. It grows at elevations from sea level to about 5,500 feet (1,676 m). It is usually found in cool lowlands such as alluvial bottoms, sandbars, stream banks, lake shores and swamps. It grows in pure stands or in the following forest types: aspen, balsam fir-paper birch, white spruce-balsam fir-paper birch, black ash-American elm-red maple, aspen-birch, white spruce-aspen, and black cottonwood-willow (Fowells 1965).
Key Plant Community Associations
Balsam poplar is a seral species that occurs primarily in ecotones
between boreal forest and tundra or prairie, and along streams and
rivers. It is most common in white spruce (Picea glauca) forests of
Canada but can extend beyond the conifer treeline in western Canada and
Alaska . Classifications including balsam poplar as a dominant
component in community types (cts), plant associations (pas), or
ecosystem associations (eas) are listed below.
Area Classification Authority
Alaska general veg. pas Viereck 1989
general veg. cts Viereck and Dyrness 1980
postfire forest cts Foote 1983
British Columbia general veg. eas Pojar & others 1984
Alberta general veg. cts Dirschl & others 1974
wc Alberta forest cts Corns 1983
Ontario forest eas Jones & others 1983
Canada general veg. pas Roi 1967
Balsam poplar generally occurs on moist sites, such as river
floodplains, stream and lake shores, moist depressions, and swamps, but
will also grow on drier sites [9,22,63,111]. It commonly grows in moist
forests, such as white and black spruce (Picea mariana) forests of the
boreal zone, and is found in the forest-tundra transition zone in Canada
[63,68]. Balsam poplar can be found growing beyond the coniferous tree
line along rivers and on southern slopes having less permafrost than the
Common associated species of balsam poplar include the following:
Canada and Alaska: white spruce, black spruce, blue spruce (Picea
pungens), lodgepole pine (Pinus contorta), jack pine (P. banksiana),
subalpine fir (Abies lasiocarpa), tamarack (Larix laricina), black
cottonwood, paper birch, aspen, alders (Alnus spp.), willows (Salix
spp.), currant, (Ribes spp.), red-osier dogwood (Cornus sericea), and
prickly rose (Rosa acicularis) [16,19,36,55,56,63,74,77,80,99].
Minnesota: balsam fir (Abies balsamea), black ash (Fraxinus nigra),
American elm (Ulmus americana), red maple (Acer rubrum), aspen, and
bitter cherry (Prunus emarginata) .
Glacial moraines in the northern boreal forest commonly support stands
of balsam poplars. Permafrost may occur discontinuously in these areas
. Typical soils where balsam poplar is found are those of alluvial
floodplains, including gravel, deep sand, clay loam, silt, and silty
loam [24,36]. Abundant soil moisture is needed, but stagnant brackish
water is intolerable to this tree . Balsam poplar has high nutrient
requirements; it needs a good supply of calcium and magnesium. It does
not tolerate acidic deep peats and humic soils in which nutrients are
released slowly .
Climates in which balsam poplars grow range from arctic to temperate
but most commonly are boreal. Average temperatures in British Columbia
boreal forests are below 26 degrees F (-3 degrees C) in the coolest
month and around 50 degrees F (10 degrees C) in the warmest month .
Mean annual precipitation is 177 inches (452 cm); about one-third is in
the form of snow .
Elevational ranges for balsam poplar are reported as follows:
feet meters reference
Alaska 0 - 3500 0 - 1067 
British Columbia 0 - 5400 0 - 1650 
Colorado 6000 - 12000 1800 - 3700 
Wyoming 3500 - 9000 1067 - 2740 
Montana 5500 1675 
Utah 4300 1310 
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the term: cover
Eastern Forest Cover Types:
1 Jack pine
5 Balsam fir
33 Red spruce - balsam fir
37 Northern white cedar
39 Black ash - American elm - red maple
Western Forest Cover Types:
201 White spruce
202 White spruce - paper birch
203 Balsam poplar
251 White spruce - aspen
252 Paper birch
253 Black spruce - white spruce
206 Engelmann spruce - subalpine fir
222 Black cottonwood - willow
235 Cottonwood - willow
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K012 Douglas-fir forest
K015 Western spruce - fir forest
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K018 Pine - Douglas-fir forest
K063 Foothills prairie
K064 Grama - needlegrass - wheatgrass
K066 Wheatgrass - needlegrass
K067 Wheatgrass - bluestem - needlegrass
K074 Bluestem prairie
K081 Oak savanna
K093 Great Lakes spruce - fir forest
K094 Conifer bog
K096 Northeastern spruce - fir forest
K098 Northern floodplain forest
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):
FRES10 White - red - jack pine
FRES11 Spruce - fir
FRES17 Elm - ash - cottonwood
FRES19 Aspen - birch
FRES21 Ponderosa pine
FRES23 Fir - spruce
FRES28 Western hardwoods
FRES38 Plains grasslands
Habitat & Distribution
Known Pests: CRYPTORHYNCHUS LAPATHI
Xanthomonas populi infects and damages cracked, cream slime oozing shoot (one year old) of Populus candicans 'Aurora'
Other: major host/prey
fruitbody of Exidia thuretiana is saprobic on dead, fallen wood of Populus candicans
Other: minor host/prey
In Great Britain and/or Ireland:
Foodplant / spot causer
mostly hypophyllous, in small groups, rarely epiphyllous and singular uredium of Melampsora laricis-populina causes spots on live leaf of Populus candicans
Remarks: season: 7-10
Foodplant / spot causer
loosely gregarious pycnidium of Phyllosticta coelomycetous anamorph of Phyllosticta populi-nigrae causes spots on dead, fallen leaf of Populus balsamifera ssp balsamifera
Remarks: season: 8
immersed, in groups of 5 to 12 perithecium of Valsa sordida is saprobic on dead branch of Populus balsamifera
Remarks: season: 2-4
Associated Forest Cover
In eastern North America, balsam poplar is found mainly in mixed stands where other species dominate. In Saskatchewan, it is a component of the following forest types: Aspen-hazelnut (Populus tremuloides/Corylus cornuta), white spruce (Picea glauca)-feathermoss, aspen-sarsaparilla (Aralia nudicaulis)/twinflower (Linnaea borealis), white spruce/aspen-bunchberry (Cornus canadensis)/bishops cap (Mitella nuda), black spruce (Picea mariana)feathermoss, and white spruce-horsetail (Equisetum spp.) (31). Balsam poplar is uncommon in boreal white spruce forests east of about 75° longitude and is not present in black spruce stands east of 85 to 86° longitude. It grows with white spruce east of 75° longitude, however (45). Other associated trees are balsam fir (Abies balsamea), paper birch (Betula papyrifera), black ash (Fraxinus nigra), American elm (Ulmus americana), red maple (Acer rubrum), tamarack (Larix laricina), and northern white-cedar (Thuja canadensis).
In western and northern parts of the range, balsam poplar is associated with balsam/alpine fir (Abies lasiocarpa), aspen, paper birch, white spruce, and black spruce on upland sites. It reaches its most widespread development on the river flood plains. On these sites, it occurs in pure stands and is associated with mountain alder (Alnus incana) and various willows (e.g., Salix alaxensis, S. interior) during early stand development and white spruce in later stages when it finally disappears from these sites (53,57).
Low shrubs associated with balsam poplar include redosier dogwood (Cornus stolonifera), bunchberry, mountain maple (Acer spicatum), bearberry honeysuckle (Lonicera involucrata), beaked hazel, American cranberry bush (Viburnum trilobum), highbush cranberry (V edule), red raspberry (Rubus idaeus var. canadensis and strigosus), prickly rose (Rosa acicularis), mountain cranberry (Vaccinium vitis-idaea), devil's club (Oplopanax horridum), and red currant (Ribes triste).
Some associated herbaceous plants are horsetails (Equisetum arvense, E. pratense), bluejoint reedgrass (Calamagrostis canadensis), bedstraws (Galium boreale, G. triflorum), fireweed (Epilobium angustifolium), panicle bluebells (Mertensia paniculata), red baneberry (Actaea rubra), alpine pyrola (Pyrola asarifolia), claspleaf twistedstalk (Streptopus amplexifolius), wild sarsaparilla, butterbur (Petasites spp.), and bishops cap.
In mixed stands, various feathermosses (e.g., Hylocomium splendens, Pleurozium schreberi) and lichens may be associated with balsam poplar. In Alaska, two mosses, Eurhynchium pulchellum and Mnium cuspidatum, have been reported in flood plain stands (53). Moss and lichen cover is generally low in these stands.
Diseases and Parasites
Fire fuels differ in the various vegetation types where balsam poplar occurs. Pure stands of balsam poplar support fires of less intensity than those in mixed conifer-hardwood stands, and tree survival is greater. Early successional stands containing only hardwoods are less likely to burn intensely than later successional stages or mixed balsam poplar-conifer stands (41). Balsam poplar produces root suckers after fire, and burned sites can be colonized by seed reproduction when mineral soil seedbeds are created.
As rivers create sites for establishment of balsam poplar, they also destroy sites with established stands. This process can be gradual as the river slowly undermines its bank at the rate of a few feet per year, or the erosion can be dramatic. It is not uncommon to see river channels change by 30 to 60 m (100 to 200 ft) in several years. These channel changes can destroy significant areas of established poplar stands.
Moose, deer, elk, and other animals browse on balsam poplar stem material but eat little foliage (3). Stems as large as 5 cm (2 in) d.b.h. may be broken by moose and the tops browsed. Where browsing occurs for only 1 or 2 years, however, form is not adversely affected because subapical buds rapidly replace damaged terminals. Simulated browsing of 9 to 14-year-old poplars resulted in increased twig biomass, indicating that only under the severest, repeated browsing is it adversely affected (16).
Resin of balsam poplar appears to repel snowshoe hares, and foliar buds have higher resin contents than internodes. As a result, hares may eat internodes of twigs and stems but not the buds (3,38). High terpene and phenolic resin content are sufficient to reduce cellulose digestion, making balsam poplar less palatable to animals (43).
Girdling by hares or rodents can kill saplings or small trees above the girdle, but dormant buds from below the girdle usually form a new stem. Ruffed grouse may feed on staminate buds in the winter.
Beaver frequently cut balsam poplar growing along watercourses; usually, sprouts are not produced or, if they are, they either die or are browsed and subsequently die. On small streams, ponds created by beaver dams can kill poplars growing in or adjacent to ponded areas.
The poplar and willow wood borer (Cryptorhynchus lapathi), bronze poplar borer (Agrilus liargus), and the poplar borer (Saperda calcarata) are among the most damaging insects. They girdle or badly weaken trees larger than 2.5 cm (1 in) in diameter by tunneling in the main stem and limbs (9).
The forest tent caterpillar (Malacosoma disstria), satin moth (Sti1pnotia salicis), gray willow leaf beetle (Pyrrhalta decora decora), and aspen leaf beetle (Chrysomela crotchi) feed on balsam poplar foliage, but the species is not their principal host (1). The highly resinous buds and leaves of balsam poplar may render them relatively less palatable than the principal tree hosts (3).
In mature trees, the most common decay-causing fungal species is Phellinus tremulae with Pholiota destruens, Corticium expallens, and Bjerkandra adusta also being important. A canker caused by Neofabraea populi has been observed on balsam poplar in Ontario less than 3 cm (1.2 in) in diameter (22,23). The occurrence of decay varies with site conditions and among clones, with the latter appearing to be the most important cause of resistance (23). Infection by Rhytidiella moroformis causes a roughening of the normally smooth bark and the formation of deep furrows. Melampsora spp. cause a leaf rust and Linospora spp., a leaf blight (22). Venturia populina causes a leaf and twig blight and can stunt the main stem.
Septoria musiva and S. populicola cause a leaf spot and canker on balsam poplar seedlings. Septoria musiva was reported to cause the highest percentage of canker and leaf spot in southern Manitoba. Septoria incidence on native poplars within their range is negligible (61).
Frost damage occurs to trees of all ages in exposed stands established after bums and logging, in nursery stooling beds, and in plantations of hybrid poplar (60). Entire twigs may be shed. Distortion from frost damage occurs adjacent to cankers, and dieback results in burl formation, bud proliferation, sucker production, and uneven development of bark, leaf, and sapwood (60).
PESTS AND DISEASE: Populus spp. have many natural enemies. The poplar and willow borer, Cryptorhynchus lapathi, is the most serious insect pest of balsam poplar and causes considerable mortality of saplings (Fowells 1965). The forest tent caterpillar, Malacosoma disstria, will only feed on the foliage of P. balsamifera when other Populus spp. (P. tremuloides and P. grandidentata) found in the same area have been completely destroyed (Fowells 1965).
Moderate browsing by mammals such as deer causes little permanent damage to suckers. Mice, voles, and rabbits can girdle suckers, and beaver frequently cut larger trees.
Fire Management Considerations
Prescribed burning for wildlife: Fire-induced poplar and willow
sprouting can increase forage for moose . Beaver also benefit from
an increased supply of poplar sprouts following fire . Repeatedly
burning white spruce forests and balsam poplar stands can convert large
areas into grasslands used by elk and Stone's sheep . Cyclic burns
(every 10 years) are needed to maintain sedge (Carex spp.) grasslands
that would otherwise be taken over by shrubs and deciduous trees,
including balsam poplar; sedges are the main food item for bison in
northern latitudes . Wood Buffalo National Park, a large bison
preserve in Canada, is characterized by extensive areas of white spruce
and mixed hardwoods, and extensive sedge meadows. Natural fire cycles
here have been estimated to be 50 years .
Fire control has had little or no impact in most of the far northern
boreal forest and natural lightning-caused FIRE REGIMES prevail .
Estimated fire intervals of white spruce stands vary from 80 years on
morainic uplands to 300 years in floodplain stands . Closed white
spruce forests of interior Alaska tend to have either high intensity
crown fires or severe surface fires which kill and regenerate entire
stands . Balsam poplar present in white spruce stands will recover
rapidly after fire . White spruce replacement may be retarded with
cyclic fires .
Balsam poplar easily colonizes large burn areas due to seed dispersal
distances and its ability to regenerate vegetatively. White spruce may
be more successful at reestablishing small burns .
More info for the terms: root sucker, succession
Balsam poplar is a pioneer species which invades disturbed wet sites by
seeding or suckering . It is among the fastest growing trees in
temperate latitudes [22,101]. Rapid early growth allows it to establish
and dominate for up to 100 years; it has lived up to 200 years in Alaska
[36,75] but is considered more short-lived in southern areas.
Balsam poplar is highly flood tolerant  and is able to form
adventitious roots within a few days of a flood . It showed no
noticeable injury from 2 months of flooding in several different areas
of Minnesota . Balsam poplar is a seral species, eventually shaded
out by other hardwoods or by conifers [14,22]. In Minnesota it is
commonly found in transition zones between prairie and conifer forest
, and it is found in the transition zone between boreal forest and
tundra in far northern latitudes .
Balsam poplar occurs on both dry and wet sites, with different factors
controlling succession on these different sites. Dry sites such as
south slopes or coarse alluvium supporting balsam poplar are affected to
a great degree by fire [75,96,97]. Fire is a major factor controlling
succession in northern montane boreal forests . Repeated wildfires
have led to the development of balsam poplar- and aspen-dominated stands
within white spruce forests  and retards white spruce replacement
. Fire will stimulate balsam poplar to root sucker and increase in
density where it is present in any successional stage . This tree
has an explosive recovery rate after even severe fires .
Fire is uncommon [40,77] and plays no apparent role in succession of
alluvial floodplain sites in boreal forests . Flood or other soil
disturbances allow colonization by willows, alders, and balsam poplars,
with balsam poplar eventually overtopping the other species and
dominating for up to 100 years [10,76,99]. Eventually white spruce
overtops the poplar and matures as an even-aged white spruce forest.
Conversion from balsam poplar to white spruce usually occurs within 120
to 150 years unless an inadequate white spruce seed source exists or
severe flooding recurs . These white spruce stands eventually
become uneven-aged and permafrost may develop due to a lack of sunlight
penetrating through to the soil. Permafrost development will lead to
replacement by black spruce and tamarack. Balsam poplar is occasionally
reported to occur in black spruce forests [17,48,49] but does not
Growth Form (according to Raunkiær Life-form classification)
Plant Response to Fire
Balsam poplar is stimulated to produce root suckers within several weeks
following fire [36,38]. Active recovery is likely to begin 1 year after
fire; balsam poplar increased in cover and frequency after 1 year on a
severely burned site in Alberta :
prefire .4 % 5 %
postfire 3.2 % 33 %
Most balsam poplar suckering occurred in the second season after a
spring burn in a 15-year-old stand in Alberta, and after 5 years poplar
density was greater on burned areas than before the fire .
Two years after logging and broadcast slash burning in a floodplain
white spruce area, white spruce seedlings were outnumbered and
overtopped by hardwood seedlings, including balsam poplar . Soil
temperatures on these sites were doubled, which encourages vegetative
expansion by balsam poplar [36,86].
See black cottonwood for further information on sprouting response of
balsam and other cottonwoods.
Immediate Effect of Fire
Severe fires kill balsam poplars ; however, underground parts
survive in moist soils . Moderate fires may top-kill some trees;
light fires usually do not harm mature balsam poplars . Young trees
may be top-killed because of their thin bark . Repeated burning may
permanently exclude balsam poplars .
survivor species; on-site surviving root crown or caudex
off-site colonizer; seed carried by wind; postfire years 1 and 2
Balsam poplar is considered one of the tree species most well adapted to
fire in the northern boreal forest . Its ability to produce sprouts
from roots, stumps, and buried branches enables it to quickly recover
after fire . The bark of older balsam poplars can be up to 4 inches
(10 cm) thick at the base, affording fire protection .
Balsam poplar reproduces both sexually and vegetatively.
Seed production and dispersal: Balsam poplar flower production begins
at about 8 years of age, with a good seed crop produced every year .
Most seeds are wind dispersed and fall within 650 feet (200 m) of the
parent tree . Seeds remain viable for 2 to 4 weeks [57,63] but will
germinate immediately following arrival on a suitable seedbed of
exposed, moist mineral soil . A 98 to 100 percent germination rate
was obtained in 2 to 3 days at temperatures ranging from 41 to 77
degrees F (5-25 degrees C) in a greenhouse study . Seedlings
require 1 month of abundant moisture to survive .
Vegetative reproduction: Balsam poplar is capable of regenerating from
root suckers, stump sprouts, stem sprouts, and buried branches [36,57].
Root suckering is thought to be primarily a means of expansion rather
than a means of recovery following clearcutting or fire . Once
established on more mesic sites, balsam poplar will expand onto drier,
sandier sites adjacent to river floodplains through vegetative expansion
. Most root suckers grow from roots about 0.4 inches (1 cm) in
diameter within the top 0.8 inches (2 cm) of soil . Suckering is
most common when the organic layer has been removed, exposing mineral
soil . Root suckering activity may increase when soil is disturbed
or when the overstory is removed, thus allowing warmer soil temperatures
. Balsam poplar suckers are larger than those of eastern and
narrowleaf cottonwood and are more vigorous than aspen suckers .
Cut stumps produce sprouts from callus tissue and from dormant buds
. Branches must be well buried to produce aerial shoots . Stem
sprouting effectively aids recovery after destructive flooding in which
the main stem is broken or bent over . Plant fragments washed
downstream may be a means of colonization for balsam poplar . In
such cases sprouts can form on either root or shoot segments, leading to
the formation of new roots and establishment of a new plant.
Stands of balsam poplar are often polyclonal, with several genotypes and
their sprouts making up a stand .
Reaction to Competition
In primary succession on river flood plains, balsam poplar is an early invader and is associated with various willows and alder for about 20 years after formation (53). It appears to assume dominance as a result of greater stature and relative growth rate than willow and alder, which precede it in succession, and white spruce, which follows it (58,59). It may have an allelopathic effect on alder germination and germinant development, but these effects have not been substantiated under field conditions (27,58,59). Balsam poplar bud extracts inhibit nitrification under laboratory conditions, indicating the potential for nitrogen conservation within poplar stands and an effect on forest development and succession (49). It is the dominant species for about 50 years. White spruce gradually replaces balsam poplar, and by age 100 to 150 years, the poplar is a minor component of the stand. Deviations from this general pattern include the Yukon and Susitna Rivers where poplar stands more than 200 years old occur, and white spruce is a minor species present mainly in the understory.
Balsam poplar can be important in secondary succession on bums and cutovers or primary succession on lakeshores and sites severely disturbed by mining and construction. Asexual and sexual reproduction are important in burned and cutover areas, but only sexual reproduction is important on severely disturbed sites. Balsam poplar can reproduce asexually under stand conditions, but the suckers are short lived.
Expansion of the root system and subsequent sucker production can play an important role in clone development and colonization of a site after the seedling ortet becomes established. Extension of lateral roots 1 to 3 cm (0.4 to 1.2 in) in diameter has been observed to be at least 14 m (46 ft) in 15-year-old clones. Expansion of the root system ranged between 0.5 and 8.0 m (1.6 and 26 ft) in a 15-year-old clone; maximum rate of expansion occurred between 5 and 9 years (33). Root system expansion determined from clone size and age appears to be lower at treeline than at lower elevations where clones of about the same size occur but are 6 to 10 times older (6,33,35.).
On sites without active soil deposition, formation of the root system is predominantly downward and lateral. Depth of rooting is restricted on the relatively wet sites where balsam poplar is commonly found. Lateral root spread on upland sites is at least 8 to 12 in (26 to 39 ft).
Life History and Behavior
Balsam poplar flowers bloom and seeds disperse before leaves completely
emerge [36,101]. Bloom and seed dispersal dates in several geographic
areas are as follows:
flowers bloom seeds disperse
Alaska [57,101] May-June June
British Columbia  April-June May-June
CO, MT, ND  April-May
Lake States, Maine & April-May May-July
In Alaska, segments of stems and branches broken and buried during autumn logging contribute to regeneration. This buried material was from 2 to 6 cm (0.8 to 2.4 in) in diameter and 10 to 200 cm (4 to 79 in) long (69).
Dormant hardwood stem cuttings, as old as 10 to 15 years and probably older, will produce roots and new shoots. Older cuttings frequently take longer to root than younger cuttings. The distal portion of the current year's growth may root more poorly than the basal part of the current growth and 2-year-old wood. In a rooting study conducted with material from Ontario, cuttings collected after December had a higher percentage of rooting, more roots per cutting, and a higher percentage of cuttings with bud activity than those collected before December. Age of the parent tree had no effect on number of roots produced or bud activity (8). Clonal differences are a major source of variation in rooting percentage and the number of primary roots produced by dormant cuttings (15). Rooting potential for hardwood cuttings ranges from 75 to 100 percent (8,24); rooting of softwood cuttings ranges from 23 to 63 percent, depending on treatment (24).
Unrooted stem sections have been used with varying success in regeneration of field sites. In one study in Alaska, survival after 3 years ranged from 15 to 82 percent. Highest survival was observed on gravel substrates, least on silt and sand soils. Third-year height was greatest on silt and sand-1.2 m (3.9 ft) (28). In a prescribed bum, survival after 5 years was generally low; microsites burned to mineral soil supported the best growth. Relatively deep organic layers, whether burned or unburned, provide a poor environment for the establishment of unrooted stem cuttings (65,66).
Stem cuttings (hardwood and softwood or greenwood cuttings) have been the major means of stand establishment for the short-rotation intensive culture of balsam poplar and hybrid poplars in Wisconsin, Ontario, and other areas (20). Hardwood cuttings are grown in clonal orchards, harvested, stored, and planted either rooted or unrooted. Clones that are difficult to root may survive better if they are regenerated from rooted cuttings. Greenwood cuttings provide a means of rapidly increasing the number of desirable clones, but they must be rooted before planting (20).
In the greenhouse, root cuttings of balsam poplar clones from Utah produced surface suckers from suppressed buds and end suckers from the cambium at the cut end (46). Root cuttings also produce new lateral roots from the same origins as suckers. Alaskan clones respond similarly (69).
Production of suckers after disturbance of the parent tree varies; the response is generally less than that of aspen which suckers prolifically. In Alaska, stocking after 3 years ranged from 4 to 61 percent; densities were 1 to 2 plants/m² (3 to 8/milacre) in harvested balsam poplar stands. Suckers made up about 80 percent of the stocking in the summer- and winter-logged areas but only 27 percent in a fall-harvested area. Production was on intact and broken roots within the upper 2 cm (0.8 in) of the surface soil. Average diameter of roots producing suckers was 1 cm (0.4 in) (69). In a 40- to 50-year-old stand on the Tanana River in interior Alaska, stocking was 83 percent and density 2 trees/m² (8/milacre) (25). In Saskatchewan, sucker regeneration was observed on dry, moist, and wet regimes. Stocking was 12 percent in the aspen-hazelnut type; 5 percent in the white spruce-aspen-bunchberry type; 5 percent in the white spruce/feathermoss type; and 7 percent in the aspen/sarsaparilla/twinflower type (31).
Density of suckers is greatest on sites where the organic layers are disturbed. Organic layers are effective insulators and may limit sprouting by controlling soil temperature, particularly in high latitude forests (69).
Production of suckers may be important in the invasion and establishment of balsam poplar on disturbed sites and in primary succession. Expansion has been observed on flood plains from established stands to areas that did not have poplar (40). Colonization by clonal expansion is believed to be more important on dry sites where the probability of seedling establishment is low (33). The area covered by individual clones on productive forest sites is not well documented; one 15-year-old clone consisted of 27 ramets and covered an area of 350 m² (3,700 ft²) (33).
The extent of clonal development is best documented at elevational and latitudinal treeline sites where seedling establishment is limited and development of stands through vegetative growth is the main means of colonization and maintenance of the species (6,35). Scattered groves of balsam poplar in the Brooks and Alaska Ranges of Alaska were found to be individual clones. Representative clones covered from 100 to 200 m² (1,060 to 2,110 ft²) and contained from 90 to 150 ramets. Clones with the oldest ramets (114 years old) were found on the Brooks Range sites. Ramets did not occur in areas with dense shrub cover (35).
New shoots also form on stumps from suppressed buds and adventitious buds developed from undifferentiated inner bark. Most originate in the inner bark at the top of the stump. Sprouting response varies with genotype and declines as tree age increases. It may be high (50 to 100/stump) initially, but production and survival of sprouts vary with season and logging method. The percentage of stumps with sprouts declines over a 2- to 5-year period (69).
Balsam poplar stump sprouts may be of little potential value in replacement of trees in mature stands after disturbance because of the fragile connection between sprout and stump. In intensively cultured stands grown on short rotations, coppicing is used to replace the new crop after harvest of the original stand established from stem cuttings. Individual cuttings may produce 10 to 20 sprouts I year after harvesting; 4 to 8 sprouts will survive after 2 years (20).
The growth potential of balsam poplar vegetative reproduction is greater than that of early seedling growth. Average height of balsam poplar was about 1 m (3.2 ft) after 3 years; height of dominants was 2.5 to 3.0 m (8.1 to 9.8 ft). The age of suckers at breast height (1.5 m or 4.9 ft) varies with site quality and the degree and type of disturbance (21,25).
The most detailed data available for growth of vegetative reproduction comes from stands of a P. balsamifera x tristis hybrid established from stem cuttings. After harvest of the original stands, coppice stands are managed for several rotations. Mean annual increment (stem plus branchwood) is 21 to 25 t/ha (9.5 to 11.0 tons/acre), depending on stand age and rotation length (11). Other studies with this hybrid have shown that 1- and 2-year-old coppice stands are taller and more productive than stands of similar age established from stem cuttings. Architecturally, the stands are different in that each individual in coppice stands has 10 to 20 stems at age 1 and 4 to 8 stems at age 2. Stands from stem cuttings usually contain one stem per individual at this age (20).
Internode length on young vegetative regeneration is usually greatest in the lower part of the annual shoot. Buds are longest in the central part of the shoot, and the terminal bud is equal to the largest nodal bud. First-order branches are smallest at the base of the previous year's growth and longest near the top. Angle of divergence of first-order branches is 30° to 40° (37).
Germination is epigeal and can occur after the seed has separated from the silky hair or in association with the hairs. Under ideal conditions, germination is rapid, and cotyledons can be expanded in 18 to 24 hours (33,64). The rate of germination declines below 15° to 20° C (59° to 68° F) (64). A conspicuous ring of fine hairs is formed at the root-hypocotyl junction. These hairs anchor the seedling to the substrate until the radicle provides a more substantial foothold. Moist mineral soil surfaces are the best seedbeds. Seeds germinate on moist organic seedbeds, but seedling survival is poor, and most seedlings die soon after germination (6,59,67).
Seedling development depends on photosynthesis soon after germination. After the first growing season, hypocotyl length varies from 2 to 5 mm (0.08 to 0.20 in) under Alaska conditions. Tricotyledonous seedlings do occur, but they are rare. Albinism can be as high as 5 percent in some seed lots in Alaska. Leaf production begins with the development of two leaves separated by 0 to 4 mm (0 to 0.16 in); the first leaf is I to 3 min (0.04 to 0.12 in) above the cotyledons. Subsequent leaf production and internode development vary by microsite and with seedling density, with maximum production of 11 leaves under field conditions in Alaska. The third and fourth internodes are the longest (25).
The height and dry weight of first-year seedlings are affected by density (25,39). Seedlings grown in a greenhouse from an Ontario seed source ranged from 5 to 32 cm (2 to 12.5 in) in height and 11 to 220 mg (0.17 to 3.4 gr) per plant as density decreased from about 59,000 to 323 seedlings/m² (39). Seedlings grown under normal environmental conditions in interior Alaska ranged from 2 to 6 cm (0.8 to 2.4 in) tall at sowing densities ranging from 73,400 to 1 seeds/m² (6,820 to 0.1/ft²). First-year shoot growth was proleptic with no branch formation unless the apex was damaged. Dry weight of leaves and stems ranged from 20 to 520 mg (0.3 to 8.0 gr) (25). Average root length varied from 9 to 13 cm (3.5 to 5.1 in).
On flood plain sites, height growth of planted seedlings in early successional stages was twice that in later stages. Growth appeared to be controlled by nitrogen availability in some stages of succession and a combination of light, water, and nutrient availability in other stages. In greenhouse studies, balsam poplar seedling biomass was greater on soils from alder stands than on those from earlier successional stages, suggesting that poplar benefits from nitrogen fixation. The growth of seedlings on early successional soils increased significantly when they were fertilized, but growth on alder soils was not affected by fertilization (58). Natural seedlings were found only in the early successional stages, and growth rate was similar in each of these stages.
Seed Production and Dissemination
Although most balsam poplar seeds die within several weeks of dispersal, some remain viable for 4 to 5 weeks. Duration of viability is dependent on temperature and moisture; cooler, drier conditions prolong viability. Viability can be maintained at 90 percent or greater for at least 3 years when seed is stored in airtight containers at -10° C (14° F) (4,63,65).
Flowering and Fruiting
The regional ratio of male to female clones was found to be 1:1 on treeline sites in northern Quebec. Female clones occurred on sites with a relatively milder climate or those that were more fertile and mesic; male clones were more common on inland sites with drier soil conditions. Most stands were made up of more than one clone; however, monoclonal stands usually contained a male clone, and polyclonal stands usually had only female clones. Stand density and area were greater in male than in female clones (6).
Flower clusters (catkins) are 5 to 9 cm (2 to 3.5 in) with many small flowers about 3 mm (0.12 in) long. Male flowers have 20 to 30 reddish stamens. Mature female catkins are 10 to 15 cm (4 to 6 in) long. Capsules are a lustrous green during development but turn dull green at time of dispersal. Male flowers are shed promptly and decay; female catkins are shed shortly after dispersal is completed but remain identifiable for the remainder of the summer (2,56).
Growth and Yield
The form or branching pattern of young trees is excurrent, with a clearly defined main bole and conical crown. In the 80- to 100-year-old age class, trees tend to have a more rounded crown, however, and the central stem gives rise to a more deliquescent or decurrent growth habit. On good sites the excurrent growth habit is present to at least 40 to 50 years. On poorer sites, the decurrent growth habit may occur earlier. The branching system is composed of long and short shoots; short shoots produce most of the leaves. Long shoots account for height growth and lateral branch extension.
Balsam poplar vegetative buds exhibit unconditional dormancy in the fall and early winter. A brief chilling period removes this dormancy, however, and by early February, buds are largely in a state of imposed dormancy with active growth commencing as soon as the temperature is high enough (14).
Specific gravity of balsam poplar wood ranges from 0.326 to 0.346 and differs among sites. Within individual trees, specific gravity varies from 0.318 to 0.429 and is greatest at the top of the tree. Fiber length ranges from 1.02 mm (0.04 in) at breast height to 0.78 mm (0.03 in) at a bole position of 75 percent of total height. Sapwood pH averages 5.40 and heartwood 8.12. No significant differences were found among male and female clones in pH or wood and bark extractives. Lignin content of wood was higher in the sapwood than in the heartwood; bark lignin content was three times greater than that of the wood (32,48).
Balsam poplar stands are generally even-aged, with some variation. On upland sites in Saskatchewan, the greatest age span is about 17 years, but most stands have an age range of 5 years or less (10). Age spans are 20 to 25 years or less in young stands and 50 to 60 years in 155- to 165-year-old stands occupying flood plain sites in northeast British Columbia (40).
The greatest age spans have been observed in the poplar groves characteristic of treeline stands. Clones in Alaska treeline stands have ramets ranging in age from I to more than 100 years old. New suckers tend to be produced at the periphery of the clone (35).
Stand density varies with stand history. The density of stems larger than 2.5 cm (1 in) varies from 8700/ha (3,250/acre) in 25-year-old stands to 225/ha (91/acre) in 200-year-old stands (53). In southern portions of the species' range, stand density is not well documented but is probably lower than in northern areas because balsam poplar does not normally occur in large pure stands. In Wisconsin, balsam poplar made up less than 2 percent of the total stand volume in the types where it was present (for example, balsam fir-white spruce, aspen, and tamarack) (12). In mixed-wood sections, balsam poplar makes up 7 percent of the total volume and annual growth (31), but this percentage varies with site type and drainage (table 1).
Table 1- Density and volume of balsam poplar in Saskatchewan by site type and drainage (adapted from 23) Site type and drainage Density Volume trees/ha trees/acre Pct of stand m²/ha ft²/acre Pct of stand Whitespruce- feathermoss,
well drained 17 7 3 11 157 5 White spruce/ aspen-bunchberry,
well drained 86 35 7 14 200 7 Aspen-hazelnut,
well drained 91 37 12 22 314 10 Jack pine-feather-moss/
club moss, moderately well drained 7 3 1 2 26 1 White spruce- feathermoss, moderately well drained 44 18 6 25 357 8
Total balsam poplar biomass estimates in Alaska range from 75 t/ha (33 tons/acre) in the Yukon River drainage to 180 t/ha (80 tons/acre) on the Tanana River flood plain for 60-year-old stands (29,68). In Alberta, aboveground dry weight for trees 16 to 65 years old varied from 0.45 to 251 kg (0.99 to 553 lb); 33 to 71 percent of this weight was in the main stem (30).
Forest survey reports for Alaska indicate that, in unmanaged stands, balsam poplar (or the hybrid with P trichocarpa) has a mean annual increment of from 4 to 6 m³/ha (57 to 86 ft³/acre) in the Susitna Valley. Site indices (base age 100 years) in British Columbia range from 6 to 12 ft (low) to 34 to 42 ft (good) (21).
Molecular Biology and Genetics
Balsam poplar and black cottonwood (Populus trichocarpa) have hybridized and produced mixed populations. Because of this intermixing, black cottonwood has been suggested as a subspecies (i.e., Populus balsamifera subsp. trichocarpa) (2,37). Where balsam poplar and black cottonwood overlap, hybrids with a range of characters intermediate to those of the two species are found. An index using capsule shape, capsule pubescence, and carpel number has been developed (2,55). Other hybrids have been reported between balsam poplar and P alba, P. laurifolia, P nigra, R simonii, P. sauveolens, P. tremula, and P tristis (7,37,69).
Barcode data: Populus balsamifera
Statistics of barcoding coverage: Populus balsamifera
Public Records: 14
Specimens with Barcodes: 23
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: T5 - Secure
Reasons: Element found throughout Canada and northern United States in riparian areas, streambanks, potholes, and floodplains; abundance unknown, but characterized as "extensive." (Harris 1990)
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
The South Dakota Natural Heritage Program lists balsam poplar as
uncommon in the state .
Global Short Term Trend: Increase of 10 to >25%
Comments: Aspen invasion of grasslands especially at the prairie-forest border has increased primarily because of fire suppression (Buell 1959, Maini 1960, Blake 1963). Aspen groves that were present in the prairie just prior to that time often were of small, brush-like trees instead of tall specimens. Increased wetland drainage probably also has encouraged aspen invasion (Buell 1960)
Undisturbed aspen clones expand into adjacent prairie when light, moisture and soil conditions are appropriate especially for vegetative growth (Maini 1966b). Vigorous root suckers emerge in the prairie at the periphery of a clone, where other woody plants also frequently invade the prairie. As these suckers grow, and crowns coalesce, aspen shades out desirable grassland species.
Rate of invasion is related to disturbance, clone phenotype, slope, wind, moisture, drainage, soil texture and climate.
Aspen persists in prairie regions because of its preference for full sun and its vigorous vegetative reproduction and clonal growth that is well-adapted to top removal (fire, cutting, browsing) and drought.
Balsam poplar is an important stabilizer of riverbanks and river islands
; it also provides habitat for a wide variety of wildlife species.
For these reasons balsam poplar growing in stream corridors should not
be logged extensively . See black cottonwood for further information
on the effects of watercourse damming and stream diversion on balsam and
Mechanical logging places balsam poplar at a competitive advantage over
spruce by creating microsites for seedling establishment . Exposure
of mineral soil favors balsam poplar seed germination . Cutting
mature balsam poplars results in sprouting from callus tissue and
dormant buds . Stump sprouting is most pronounced on winter logged
areas. Improper harvesting can cause poplars to be suppressed, with
shrubs dominating the clearings . Trees cut in the summer have few
surviving sprouts after four years . Decay is a limiting factor in
balsam poplar utilization , but with proper management practices, it
could become a very important crop tree in Canada .
Balsam poplar has an allelopathic effect on green alder (Alnus viridis
spp. crispa) .
Balsam poplar can be controlled by 2,4-D + picloram , glyphosate,
and hexazinone , and has an intermediate reaction to 2,4-D and
2,4,5-T . This tree is very sensitive to sulfur dioxide fumigation
caused by landfill fires . In an area less than 10 acres (4 ha)
away from one such fire, many balsam poplars were killed.
Diseases and insect pests of balsam poplar have been discussed by
several authors [21,32].
Relevance to Humans and Ecosystems
Value for rehabilitation of disturbed sites
Balsam poplar is an important riparian species which stabilizes river
banks and maintains river islands . It is able to recolonize sites
disturbed by fire or logging [36,57].
Balsam poplar is successful at naturally colonizing borrow pits in
continental tundra regions of northwestern Canada . This tree was
found growing on six separate abandoned coal mine sites in the Rocky
Mountain foothills of Alberta . It has also been documented as
invading and expanding on mining spoils in northern Minnesota .
Balsam poplars artificially planted in a heavily burned black spruce
area had the highest survival rate of all seeded species . Balsam
poplar does not naturally colonize black spruce sites after fire
Information on greenhouse propagation and plantation establishment of
balsam poplars is available [22,39,43,63,88].
during one or more seasons for wildlife species is as follows :
WY MT ND
Pronghorn poor ---- ----
Elk good ---- ----
Mule deer good poor ----
White-tailed deer good fair good
Small mammals ---- good poor
Small nongame birds good fair fair
Upland game birds good fair fair
Waterfowl poor ---- ----
It was rated as the least preferred moose browse species in Alaska and
Canada, usually comprising less than 1 percent of moose diets
[20,64,79,109]. Bark stripping occurs on balsam poplars by moose in
times of winter food shortage . Balsam poplars with more than 50
percent of the trunk circumference debarked have a high probability of
dying; new bark may grow back on less damaged trees .
Snowshoe hares utilize balsam poplar in times of food shortage.
Snowshoe hares ignore first year growth of juvenile balsam poplars but
ring the bark of mature trees and eat the twigs when within reach .
Apparently 2,4,6-trihydroxydihydrochalcon 1, a chemical antifeedant for
hares, is present in juvenile balsam poplars . Balsam poplar
growing in the shade of thinleaf alder (Alnus incana spp. tenuifolia) is
more palatable to snowshoe hares than balsam poplars growing in
well-insulated willow thickets, due to differences in states of carbon
stress and amounts of phenolic concentrations in the poplars .
The degree of use shown by livestock and wildlife species for
balsam poplar in several western states is rated as follows .
WY ND MT
Cattle ---- fair ----
Sheep ---- fair ----
Horses ---- fair ----
Pronghorn poor ---- ----
Elk fair ---- ----
Mule deer fair ---- poor
White-tailed deer fair poor poor
Small mammals good ---- ----
Small nongame birds fair ---- ----
Upland game birds poor poor ----
Waterfowl poor ---- ----
Wood Products Value
Balsam poplar is considered a commercial tree in the northern Lake
States, with biomass yields ranging from 1 pound per acre (1.12 kg/ha)
in paper birch (Betula papyrifera) communities to 116 pounds per acre
(129 kg/ha) in white spruce communities of Michigan . Biomass
yields in Alaska average 2.2 pounds per acre (2.5 kg/ha) . Poplars
(Populus spp.) represent a substantial yet relatively unused forest
resource in Canada [46,50]. Annual harvest of balsam poplar in Canada
is less than 1 percent of the allowable cut .
Balsam poplar is used for pulpwood, lumber and veneer, and to make
high-grade paper and particle board . It is also used to make boxes
and crates .
Importance to Livestock and Wildlife
grass understories have a high grazing capacity .
Boreal forests containing balsam poplar support a wide variety of
wildlife including moose, elk, Stone's sheep, mountain goat, mountain
caribou, mule deer, wolf, coyote, black bear, grizzly bear, lynx,
snowshoe hare, wolverine, pine marten, and beaver .
Moose [20,63,64,67,71,79,109], deer [63,71], and snowshoe hare
[13,47,108] eat balsam poplar to a small extent. Voles may damage
cottonwoods by eating the roots .
Beavers use balsam poplar for food and building materials. Beaver
activity creates additional habitat for birds and other aquatic
Balsam poplar hybrids have a potential for a variety of uses. Populus balsamifera x R deltoides (Populus x jackii) are used as windbreak and shelterwood plantings in the northern plains region. Other balsam poplar hybrids are being tested in short rotation, intensive culture plantations. When properly cultivated, irrigated, and fertilized, these hybrids yield about three or four times as much biomass as native aspen in northern Wisconsin. The resulting pulpwood is of acceptable quality. The foliage and small woody component can be converted to an animal feed supplement (26,70).
Balsam poplar and its hybrids are used or have potential value in urban forestry and soil stabilization projects, particularly in the northern portion of the range and in the plains area of western Canada where the number of indigenous species available for these purposes is limited. In urban situations, however, balsam poplar has several undesirable traits. The branches of older trees tend to be brittle, female trees produce large amounts of residue from the spent catkins, and relatively rapid root suckering can result in unwanted colonization of lawns, sidewalks, and roadways.
Anyone that has ever walked into a poplar stand in the spring at bud break is impressed with the fragrance in the air. This fragrance comes from the volatile compounds in the buds and other parts of the tree. These compounds have been identified and may have useful biological and esthetic properties (38). Various extracts from the winter buds of poplar were recognized by native peoples as having therapeutic value. For example, a salve or ointment (balm of Gilead) made by heating the winter buds in oil was used to relieve congestion (52). In recent years, the bark has been collected and carved into figures that are sold in gift shops.
Names and Taxonomy
Comments: As treated here (following Kartesz, 1994), includes as a subspecies the plants often called Populus trichocarpa, the black cottonwood. LEM 17May95.
subsp. balsamifera. Black cottonwood (Populus balsamifera subsp.
trichocarpa) is the other subspecies of Populus balsamifera .
For information on black cottonwood, see that FEIS review.
Balsam poplar hybridizes with black cottonwood in Alaska,
where ranges of the two trees overlap . It also hybridizes with
narrowleaf cottonwood (P. angustifolia) [35,61], eastern cottonwood (P.
deltoides) [35,61], and rarely with aspen (P. tremuloides) [61,101].
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