is the common name of a genus
) belonging to the
family (Family Betulaceae
). The genus comprises about 30 species of monoecious
trees and shrubs, few
reaching large size, distributed throughout the North Temperate Zone and in the
Americas also along the Andes southwards to Argentina.
), alternate, simple, and serrated. The
with elongate male catkins on the same plant as shorter female
catkins, often before leaves appear; they are mainly
wind-pollinated, but also visited by bees
small extent. They differ from the birches
, the other genus in the family) in that the female
catkins are woody and do not disintegrate at maturity, opening to
release the seeds in a similar manner to many conifer cones
The largest species are Red Alder
) on the west coast of North
and Black Alder
), native to most of Europe
widely introduced elsewhere, both reaching over 30 m. By contrast,
the widespread Green Alder
) is rarely more than a 5 m tall shrub.
As soil enrichers
Alders establish symbioses
-fixing Actinobacteria Frankiella alni
bacteria converts atmospheric nitrogen into soil-soluble nitrates
which can be utilized by the alder, and
favorably enhances the soil fertility. Alders benefit other plants
growing near them by taking nitrogen out of the air and depositing
it into the soil in usable form; fallen alder leaves make very rich
As pioneer species
Alders are sturdy and fast-growing, even in acidic and damaged
sites such as burned areas and mining
Italian Alder is particularly useful on dry, infertile sites.
Alders can be used as a producer of simple bio-mass, growing
quickly in harsh environments.
As wildlife fodder
Alder catkins are one of the first sources of pollen for bee
species, especially honeybees
, which use it for spring buildup. Alders
are also used as a food plant by some Lepidoptera
) species, see list of Lepidoptera that
feed on alders
As a shelterbelt
also exceptionally good windbreaks and are
planted on the west coast of Scotland to shelter
Alder lumber is an important fast growing renewable resource used
in a wide range of applications including furniture, cabinets,
panel systems and special products. Alder has a fine close-grained
structure and is easily stained and finished. Part of the
popularity of Alder lumber is due to the unusually wide range of
grades that are available . Each grade is optimized for a
functional and/or economic aspect of a product, with visible
surfaces, structural components and hidden parts typically using
Alders are also grown in gardens, and are sometimes made into
In musical instrumentation
Alder is popular as a material for electric guitar
bodies, used by many guitar
makers such as Fender and Jackson. Alder provides a brighter tone
than other woods (such as mahogany), and—as alder is not a
particularly dense wood—it provides a resonant, well-rounded tone
with excellent sustain. Alder is also occasionally used to make
harps, although this is a rarity.
Alder is a preferred wood for charcoal
making, formerly used in the manufacture of gunpowder
, or for smelting
Alder bark (Alnus glutinosa) with
characteristic lenticels and abnormal lenticels on callused
In fish smoking
The wood is also traditionally used for smoking fish
, though this usage has often been replaced by
other woods such as oak
An exception is the smoked Pacific
industry in the Pacific
, where alder smoking is essentially universal. This
is partly due to indigenous traditions of food preservation in the
area, and partly because oak, hickory, mesquite
and other woods favored for smoking
elsewhere are not locally available in any large quantities.
Species used for Pacific salmon smoking are Red alder A. rubra
and to a lesser extent
Sitka alder A. viridis
As a dye
In the 17th century it is recorded that in Ayrshire that alder bark
was collected and used for tanning.
A whole root nodule.
Alder is particularly noted for its important symbiotic
relationship with Frankia
alni, actinomycete filamentous
. This bacterium is found in root nodules
which may be as large as a human
fist, with many small lobes and light brown in appearance. The
bacterium absorbs nitrogen
from the air and
makes it available to the tree. Alder, in turn, provides the
bacterium with carbon
, which it produces
. As a result
of this mutually-beneficial relationship, alder improves the
of the soils
where it grows, and as a pioneer species
, it helps provide additional
nitrogen for the successional
species which follow.
The common name alder
is derived from an old Germanic
root. Alsofound to be the
translation of the Old French "verne" for alder or copse
of alders. The botanic name Alnus
the equivalent Latin
name. Both the Latin and
the Germanic words derive from the Proto-Indo-European
, meaning "red" or "brown", which is also a root for
the English words elk
and another tree: elm
tree distantly related to the alders.
Edibility and medicinal uses
Alder catkins are edible and high in protein. Although they are
reported to have a bitter and unpleasant taste, they are best
remembered for survival purposes. Alder wood is also commonly used
to smoke various food items.
Alder bark contains the anti-inflammatory salicin
which is metabolized into salicylic acid
in the body. Native Americans
used Red Alder bark (Alnus
to treat poison oak, insect bites, and skin
irritations. Blackfeet Indians used an infusion made from the bark
of Red Alder to treat lymphatic disorders and tuberculosis. Recent
clinical studies have verified that red alder contains betulin
shown to be effective against a variety of tumors.
The genus is divided into three subgenera:
Trees. Shoot buds
stalked. Male and female catkins produced in autumn (fall) but
staying closed over winter, pollinating in late winter or early
spring. About 15-25 species, including:
Trees or shrubs.
Shoot buds stalked. Male and female catkins produced in autumn
(fall) and expanding and pollinating then. Three species:
Shrubs. Shoot buds
not stalked. Male and female catkins produced in late spring (after
leaves appear) and expanding and pollinating then. One to four
Green Alder (Alnus viridis
- Alnus viridis — Green
- Alnus viridis subsp. viridis. Eurasia.
- Alnus viridis subsp. maximowiczii (A.
- Alnus viridis subsp. crispa (A.
crispa). Northern North America.
- Alnus viridis subsp. sinuata (A.
sinuata, Sitka Alder or Slide
Alder). Western North America, far northeastern Siberia.
glutinosa and A. viridis are classed as environmental
weeds in New
illustrated in the coat of arms for the Austrian town of Grossarl.
- Chen, Zhiduan and Li, Jianhua (2004). Phylogenetics and
Biogeography of Alnus (Betulaceae) Inferred from Sequences of
Nuclear Ribosomal DNA ITS Region. International Journal of
Plant Sciences 165: 325–335.