Alnus alnobetula

Alnus is from an ancient Latin name derived from the Celtic meaning "growth along streams". Alnus alnobetula is sometimes planted on streambanks for flood control and erosion. Alnus alnobetula is native to the U.S. and is in the Betulaceae (Birch Family).

Photo Credit: © Chris Evans, River to River CWMA, Bugwood.org.

Alnus alnobetula

Common Name: green alder

Other Scientific Names: Alnus viridis

Plant Functional Group: Deciduous broadleaf

Class > Order > Family: Magnoliopsida > Fagales > Betulaceae

What does the species look like? Alnus alnobetula is a fast-growing, perennial, large shrub or small tree reaching 12 to 36 feet in height. The bark is grayish-brown and smooth with raised pores (lenticels). The leaves of green alder are shiny, dark green, leathery, and fine-toothed along the edges. The male flowers are clustered yellow-green to brown catkins; female flowers are more cone-like in shape (strobiles). The fruits are oval, light brown, single-seeded, winged nuts (samaras) arranged on stalked clusters. Alnus alnobetula can be found along streambanks, sandy lakes, shorelines, and bog edges, and on sandy or gravelly slopes or flats. This species can grow either alone or in thickets, and tolerates part shade to full shade and moist to wet, sandy soils. Green alders form nitrogen-fixing nodules on their roots with Frankia, an actinobacteria. Moose, caribou, and small mammals eat the twigs and foliage of Alnus alnobetula. Birds eat the seeds, buds, and catkins.

Where is the species found?

States & Provinces

AB, AK, BC, CA, ID, MA, MB, ME, MI, MN, MT, NB, NC, NH, NL, NS, NT, NU, NY, ON, OR, PA, PE, QC, SK, TN, VT, WA, WI, WY, YT

Special Considerations for Observing

If drought seems to be the cause of leaf color or fall for a plant, please make a comment about it for that observation.

This species has separate male and female flowers. If you know whether the flowers you are observing are male or female (or both), please make a comment about it for that observation.

Which phenophases should I observe?

	Do you see...?
Leaves	Breaking leaf buds One or more breaking leaf buds are visible on the plant. A leaf bud is considered "breaking" once a green leaf tip is visible at the end of the bud, but before the first leaf from the bud has unfolded to expose the leaf base at its point of attachment to the leaf stalk (petiole) or stem. More... How many buds are breaking? Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000
	Leaves One or more live, unfolded leaves are visible on the plant. A leaf is considered "unfolded" once its entire length has emerged from a breaking bud, stem node or growing stem tip, so that the leaf base is visible at its point of attachment to the leaf stalk (petiole) or stem. Do not include fully dried or dead leaves. More... What percentage of the potential canopy space is full with leaves? Ignore dead branches in your estimate of potential canopy space. Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Increasing leaf size A majority of leaves on the plant have not yet reached their full size and are still growing larger. Do not include new leaves that continue to emerge at the ends of elongating stems throughout the growing season. More... What percentage of full size are most leaves? Less than 25% 25-49% 50-74% 75-94% 95% or more
	Colored leaves One or more leaves show some of their typical late-season color, or yellow or brown due to drought or other stresses. Do not include small spots of color due to minor leaf damage, or dieback on branches that have broken. Do not include fully dried or dead leaves that remain on the plant. More... What percentage of the potential canopy space is full with non-green leaf color? Ignore dead branches in your estimate of potential canopy space. Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Falling leaves One or more leaves with typical late-season color, or yellow or brown due to other stresses, are falling or have recently fallen from the plant. Do not include fully dried or dead leaves that remain on the plant for many days before falling. More...
Flowers	Flowers or flower buds One or more fresh open or unopened flowers or flower buds are visible on the plant. Include flower buds or inflorescences that are swelling or expanding, but do not include those that are tightly closed and not actively growing (dormant). Also do not include wilted or dried flowers. For Alnus alnobetula, the male inflorescence is a catkin which is initially compact and stiff, but eventually unfolds to become longer and hang loosely from the branch. The female inflorescence is also a catkin which is very small, reddish, and has leafy scales. Once the female flowers wilt, the catkin turns green and grows thicker as the fruits develop. More... How many flowers and flower buds are present? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), simply estimate the number of flower heads, spikes or catkins and not the number of individual flowers. Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000
	Open flowers One or more open, fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between or within unfolded or open flower parts (petals, floral tubes or sepals). Do not include wilted or dried flowers. For Alnus alnobetula, the male flowers will open once the initially compact catkin has unfolded and is hanging loosely. Female flowers are open when the pistils are visible, but will be very difficult to see where they are out of reach. More... What percentage of all fresh flowers (buds plus unopened plus open) on the plant are open? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), estimate the percentage of all individual flowers that are open. Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Pollen release One or more flowers on the plant release visible pollen grains when gently shaken or blown into your palm or onto a dark surface. More... How much pollen is released? Little: Only a few grains are released. Some: Many grains are released. Lots: A layer of pollen covers your palm, or a cloud of pollen can be seen in the air when the wind blows
Fruits	Fruits One or more fruits are visible on the plant. For Alnus alnobetula, the fruit is a winged nutlet that ripens to tan or gold and is hidden within a small, scaled cone that changes from green to dark brown and whose scales are closed together. Do not include empty cones that have already dropped all of their nutlets. More... How many fruits are present? Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000
	Ripe fruits One or more ripe fruits are visible on the plant. For Alnus alnobetula, a fruit is considered ripe when the cone scales have begun to spread apart to expose the tan or gold nutlets. Do not include open cones that have already dropped all of their nutlets. More... What percentage of all fruits (unripe plus ripe) on the plant are ripe? Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Recent fruit or seed drop One or more mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind, or empty fruits that had long ago dropped all of their seeds but remained on the plant. More... How many mature fruits have dropped seeds or have completely dropped or been removed from the plant since your last visit? Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000

What do these phenophases look like?

There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.

ITIS information for green alder (ITIS TSN: 184199 )

USDA PLANTS profile for green alder (USDA Symbol: ALVI5 )

Alnus alnobetula

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