Speckled Alder

Alnus incana var rugosa

Description & Overview

Speckled Alder gives back what it takes ten-fold. Often found in areas with wet soil in or along swamps, meadows, and streams, Speckled Alder often serves as erosion control along banks while providing protection, shelter, and food to many species. It’s a nitrogen-fixing species, replenishing the soil and nourishing the plants growing around it. We typically grow it as a small tree, but it tends to take the form of a multi-stemmed shrub when left to grow in the wild.

Core Characteristics

Mature Height: 15-25 feet
Mature Spread: 6-15 feet
Growth Rate: Fast
Growth Form: Tree, Single or Multiple Stem
Light Requirements: Full Sun to Partial Shade
Site Requirements: Moist to Wet, Well-Drained Soil. Tolerates Clay, Occasional Flooding, Wet Sites.
Flower: Catkin
Bloom Period: March-April
Foliage: Dark Green
Fall Color: None
Fruit Notes: Winged Nutlets

Suggested Uses:

Use this tree to naturalize a landscape with wet soil. This tree has a big impact on the ecosystem.

Due to its tendency to sucker and spread, Speckled Alder is a great plant to use for erosion control. Its nitrogen-fixing capabilities make it perfect for a site with depleted soil. Its love of wet soil makes it perfect for a wetland garden or for use along a stream.

Speckled Alder can be trained to be a tree by cutting suckers and lower branches to expose the trunk.

Wildlife Value:

Stems are snacked on by deer, muskrats, beaver, rabbits, and others. Songbirds and gamebirds eat the seeds and catkins. Beavers use the wood to build their dams. This plant can grow in dense thickets if planted in disturbed areas, providing shelter to animals large and small from moose to mice.

Commonly found along streams, Speckled Alder affects not only the bank but the water below. It controls erosion on the bank, preventing the buildup of sediment along the bottom of a stream thus keeping gravel beds clean for spawning trout. Its shade keeps the soil cool and, if the stream is small enough, it may even aid in keeping the water cool. Cool water is essential to Trout as a cold water species as it maintains oxygen levels in the water high enough to support trout and encourages successful spawning as this can only happen in cooler temperatures.

Speckled Alder is a host plant to a significant number of moths and butterflies. Just a small sampling: Pepper-and-salt Geometer (Biston betularia), Bluish-Spring Moth (Lomographa semiclarata), Hübner’s Pero Moth (Pero ancetaria), Maple Spanworm Moth (Ennomos magnaria), Straight-lined Plagodis Moth (Plagodis phlogosaria), White Slant-line (Tetracis cachexiata), Luna Moth (Actias lunata), Banded Tussock Moth (Halysidota tessellaris), Dark-spotted Palthis Moth (Palthis angulalis), American Dagger (Acronicta americana), Walnut Sphinx Moth (Amorpha juglandis), Poecila Sphinx Moth (Sphinx poecila), Apple Sphinx (Sphinx gordius), Columbia Silkmoth (Hyalophora columbia), Green Comma (Polygonia faunus), Pale Alder Moth (Tacparia detersata), Fingered Dagger Moth (Acronicta dactylina), Autumnal Moth (Epirrita autumnata), Gray Dagger Moth (Acronicta grisea), Macaria exauspicata, St. Lawrence Tiger Moth (Platarctia parthenos), Reticulated Fruitworm Moth (Sparganothus reticulatana), Three-lined Leafroller Moth (Pandemis limitata), White-marked Tussock moth (Orgyia leucostigma), Cecropia Moth (Hyalophora cecropia), American Angle Shades (Euplexia benesimilis), and Doubleday’s Baileya (Baileya doubledayi). Wow!

While we are on the subject of the interconnectedness of it all, it is important to note that the nitrogen-fixing capacity of Speckled Alder replenishes the soil which in turn readies that soil for many other plant species that would in turn also have significant benefits for wildlife.

Maintenance Tips:

Cut off suckers as they form to keep it in tree form if that is what is desired.


Alder psyllid and Alder blight aphids can damage leaves. Can also get powdery mildew and leaf curl. Leaf miners, tent caterpillars, lace bugs, and flea beetles can be found on Speckled Alder.

Leaf Lore:

“Speckled” in the common name refers to the white lenticels along the twigs.

Timber trees grown amongst Speckled Alder have a demonstrably higher yield due to their nitrogen-fixing capabilities.

European Black Alder is an invasive exotic. Smooth Alder and Speckled Alder are the two native North American Alder species. Speckled Alder has a more northern range from North Dakota to Northern Illinois. These two natives do hybridize where their ranges overlap.

Not only does Speckled Alder sucker when growing wild, but it’s also capable of “layering.” Low-growing branches have the potential to take root and separate from the mother plant to grow separately. Neat!

Historically used by Native Americans to treat many ailments from backaches to bleeding to childbirth.

Companion Plants:

There are many options for similar plants that enjoy wet soils, including:

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