- Alnus, from the Latin for the alder
- viridis, from the Latin, "green"
- crispa, from the Latin, "curly"
- Other common names include American Green Alder, Mountain Alder, Tag
Alder, Aulne Vert, Aulne Crisp (Qué)
- Kingdom Plantae, the Plants
- Division Magnoliophyta, the Angiosperms (flowering plants)
- Class Magnoliopsida, the Dicotyledons
- Subclass Hamamelididae
- Order Fagales
- Family Betulaceae, the Birches
- Taxonomic Serial Number: 181894
- Also known as Alnus alnobetula, Alnus ovata, Alnus crispa, Alnus
crispa var. elongata, Alnus crispa var. mollis,
Alnus crispa fruticosa, Alnus X hultenii,
Duschekia viridis, Alnus viridis var. crispa,
Alnus viridis ssp. fruticosa.
- A tall, deciduous, thicket-forming, rhizomatous shrub or small tree,
to 10' tall, occasionally 20'-30'.
- Leaves ovate or elliptic; glabrous above, but pubsecent
below, lightly to heavily resin-coated. Margins serrated with very fine
teeth. Do not turn color, but remain green until dropped in the fall.
- Twigs have sessile, pointed axillary buds.
- Bark smooth, yellowish-brown, with small, scattered
- Roots shallow, with nodules containing nitrogen-fixing
- Flowers: Male catkins and female flowers on same
- Staminate catkins in single cluster of 2-4, formed
late in growing season before flowering and exposed during winter
- Pistillate catkins in 1 or more clusters of 2-10,
formed season before blooming, enclosed in buds during winter, exposed
with new growth in spring.
- Fruit a small, dry woody cone on long, thin stems.
- Seed a samara, elliptic to obovate, with wings wider
- Identifiable as an Alder/Hazel by its coarse, toothed leaves and shrubby
- Distinguished from other Alder/Hazel with some difficulty
- Field Marks
- Northwest Territories to Labrador, Newfoundland, and Greenland; south
to the Prairie Provinces, NE Minnesota, Northern Wisconsin, the UP,
Northern New York, Vermont, New Hampshire, Maine, and the Maritimes.
Isolated populations in the Appalachians.
- From open tundra to open conifer forest but cannot withstand a dense
overstory. Singly or in thickets along streams, lakeshores, coasts,
bogs, or muskeg margins, and as an understory component in conifer forests.
Usually associated with some source of moisture, but is adapted to somewhat
drier conditions than other alders. Wetter sites are more favorable
for high nitrogen-fixing activity.
- Soil textures range from sandy to gravelly or rocky; often occurs
on morainal soil left by retreating glaciers. Soils in deglaciated areas
are generally acidic (pH 5.0-6.5).
- Semi-shade tolerant and considered a pioneer species. After fire,
sprouts from the root crown and establishes by seed from plants in adjacent
unburned areas. The bare mineral soils created by these disturbances
are prime sites. These shrubs provide shade that reduces soil temperatures,
allowing spruce and other genera to establish.
- A dominant or codominant in a variety of habitats, it may occur as
an understory dominant in open conifer forests with Black Spruce (Picea
mariana), White Spruce (Picea
glauca), and Jack Pine (Pinus
banksiana) overstories; and in open and closed deciduous forests
with Paper Birch (Betula papyrifera),
Quaking Aspen (Populus tremuloides),
Balsam Poplar (Populus balsamifera),
- Can be a major competitor of conifer seedlings. Dense thickets can
prevent conifer establishment over large areas. However, due to its
nitrogen-fixing ability, alder can improve soil fertility. It is also
a nurse tree for conifers such as spruce (Picea spp.) and pine
(Pinus spp.) on nitrogen-deficient soils.
- Survives fire through persistent root crowns. Sprouting occurs from
underground stems at or within 2" of the soil surface.
- Fire kills the aboveground portion of the plant. Root crowns in the
mineral soil burn only under the most severe conditions, but they can
be killed by the heat generated during a fire. Severe fires that remove
the organic layer and expose and char root crowns can completely eliminate
- Open-growing alders more vulnerable to fire than thicket-growing alders
because very little understory fuel accumulates in alder thickets.
- Considered a survivor species, sprouting from basal or underground
parts following fire. Additionally, its wind-dispersed seeds quickly
colonize bare mineral soils exposed by fire. Regeneration from sprouting
and the establishment of seedlings allow reestablishment at a fairly
rapid rate following fire. Very adaptable and successful regardless
of length of the fire cycle. Does not burn easily, and dense stands
can sometimes prevent fire spread. The sprouting response is usually
immediate and generally results in an increased number of plants. American
green alder also reestablishes by seed dispersed from adjacent, unburned
areas. Abundant in areas with a history of frequent fires. This nitrogen-fixing
alder may be favored over other invading species by severe fires that
remove the surface organic matter. Alder invasion and persistence are
favored by fire, but total recovery is slow. Repeated fires in wet sites
can result in thickets of alder.
- Trees: Balsam Fir (Abies
balsamea), Red Maple (Acer
rubrum), Paper Birch (Betula
papyrifera), Black Spruce (Picea
mariana), Jack Pine (Pinus
banksiana), Red Pine (Pinus
resinosa), White Pine (Pinus
strobus), Pin Cherry (Prunus
pensylvanica), Red Oak (Quercus borealis), Northern
Pin Oak (Quercus ellipsoidalis), Bur Oak (Quercus macrocarpa),White
Cedar (Thuja occidentalis)
- Shrubs: Juneberries (Amelanchier
spp.), Sweet Fern (Comptonia peregrina),
Bunchberry (Cornus canadensis),
Beaked Hazel (Corylus cornuta),
Low Bush Honeysuckle (Diervilla lonicera),
Trailing Arbutus (Epigea repens), Creeping Snowberry (Gaultheria
hispidula), Wintergreen (Gaultheria
procumbens), Common Juniper (Juniperus
communis), Twinflower (Linnaea borealis),
Fly Honeysuckle (Lonicera canadensis),Willows (Salix spp.),
Late Low Blueberry (Vaccinium angustifolium)
- Herbs: Wild Sarsaparilla (Aralia
nudicaulis), Large Leaf Aster (Aster
macrophyllus), Sedges (Carex spp.), Moccasin Flower
(Cypripedium acaule), Dwarf Rattlesnake Plantain (Goodyera
repens), Canada Mayflower (Maianthemum
canadense), Cow Wheat (Melampyrum linare), Bracken
Fern (Pteridium aquilinum),
Starflower (Trientalis borealis)
- Ground Covers: Reindeer Mosses (Cladonia
spp.), Dicranum Mosses (Dicranum spp.), Clubmosses (Lycopodium
spp.), Schreber's Feathermoss (Pleurozium schreberi), Hair
Cap Moss (Polystrichum commune), Other Lichens and Mosses.
- Fungi: All of the alders associate symbiotically
with species of the actinomycete Frankia , leading to the formation
of nodules on the roots of the plants and the fixation of atmospheric
- Mammals: Consumed in small quantities by deer. In
some areas, however, it is utilized heavily by moose and caribou. Muskrat,
beaver, cottontail, and snowshoe hares feed on alder twigs and foliage.
- Birds: Many birds eat alder seeds, buds, and catkins.
- Bark is very astringent and has been used medicinally by Native Americans.
- It has also been used in the tanning of leather and dying of textiles.
- Reproduces by seed and vegetatively by rhizomes. Germination from
seed on disturbed habitats is the primary form of reproduction. The
seeds invade and colonize bare mineral soil.
- Sexual reproduction: Monoecious. Wind pollinated.
The female catkins turn woody and conelike at maturity.
- Flowers May/June
- Fruits mature in July.
- Winged seeds ripen late August/September
- Seeds dispersed by the wind through April. Germination usually
requires exposed mineral soil..
- Vegetative reproduction: Sprouts from the root crown
if damaged or cut. Sprouting often occurs after natural disturbances
such as fire.
- The pistillate catkins emerge before or with the leaves in spring;
staminate catkins are produced during the previous growing season. Cones
ripen from mid-September to mid-November, depending on latitude and
elevation, and seed dispersal takes place immediately thereafter.
- Seed and seedling stock seldom available commercially, though seed
are easily shaken from dried cones collected in September and October.
- In the nursery, fresh seed should be broadcast and drilled into washed
sand or a sand-humus mixture. Seedbeds should be mulched for overwinter
protection with mulch removed prior to germination in the spring.
- Spring planting requires stratification in moist sand or vermiculite
for 60-90 days. Seedbeds should be kept moist and shaded until late
in the summer. Two or three year-old seedlings should be used for field
planting. Site preparation requires sod layer removal to prevent herbaceous
- Hardy to USDA Zone 2 (average minimum annual temperature -50ºF)
- Good choice for wildlife plantings, disturbed site rehabilitation,
and providing streambank stability and erosion control.
- Nitrogen-fixing, symbiotic bacteria in root nodules make alder valuable
for soil conditioning.
- Can be established on cool, moist sites by direct seeding or planting
2 and 3 year-old seedlings. Nondormant seeds should be sown in the spring
and dormant seeds in the fall. Unstratified seeds will germinate but
at a slower rate than stratified seeds.
- Overgrown thickets cut in the spring or winter will rapidly regrow.
Last updated on
5 March, 2006