Speckled Alder (Alnus rugosa) and Downy Alder (Alnus crispa)


One of our largest and most common shrubs, growing to 25 feet (7.6 m), and forming dense clumps. Bark is brown to blackish-gray and speckled with many white spots. Flowers are non descript. Male and female flowers appear on separate catkins which form the previous fall. The males are slender and cylindrical and hang in clusters of 3-5 from short leafless branches. Females are cone-like, 1/4 inch to 3/8 inch (6-9 mm) long. Leaves are alternate, oval and toothed. They are dark green above, lighter below and have prominent veins. Buds are set away from twigs on 1/4 inch (6 mm) stalks. Another native alder (downy or mountain alder, which can be substituted in any plantings on drier sites) has pointed buds tight to the stem.

 Growing Conditions: 

Alder is one of the first species to invade abandoned fields, espically those which are poorly drained. It is also quite common along stream banks and roadside ditches. It makes its best growth in full sun, but is often found growing in the shade along streams.


This species is the most easily propagated by transplants, since they are common along most roadways and even some forest roads. Many farmers will allow you to transplant from their fields. Best results come from newly-invaded fields, where you find transplants between 1-2 feet (30-60 cm) tall. We are growing some from seed at MacPhail Woods – it is easy seed to collect, since the crops are heavy and need little cleaning. Seeds cluster in strobiles, almost like cones, and can be collected from late September onwards. When dry, the strobiles can just be rubbed together between your hands to release the seeds. Sprinkle over a seed bed and cover with a light layer of soil or sand, then mulch for the winter. They should germinate the next spring.

Wildlife Uses:

Alder seeds are a favorite winter food of common redpoll, pine sisken and American goldfinch and are eaten by dozens of other species. The shrubs are valuable as cover and nesting sites for many birds. Earthworms, found in abundance in the nitrogen-rich soil under alders, are the preferred food of the American woodcock. Because of this, woodcock feed, nest, and rear their young almost exclusively on the ground beneath alders. During the late spring evenings, the males perform an impressive courtship dance in fields next to alder patches. In winter, ruffed grouse eat buds and snowshoe hare browse the twigs. Beaver eat alder bark and use the stems for dam and lodge construction.

Areas of Usage:

Alders are generally regarded as a nuisance, though this attitude is beginning to change. They are not one of our more attractive shrubs, but are very useful in windbreaks, preventing erosion along stream banks and building up depleted soils. Alders can annually add up to 140 lbs/acre (160 kg/hectare) of nitrogen to the soil by bacteria in nodules on roots and leaf fall. They have a great potential in small forest plantations, providing some shade and protection while enriching soil for more valuable trees. Along streams, alders prevent erosion and provide excellent overhanging shade for trout.

Additional Information:

The speckled alder, common throughout PEI is a low, crooked, often declining shrub from 6 to 15 feet in height and a diameter up to 4 inches. It often grows in clumps of many stems which branch close to the ground. It is commonly found in thickets along streams, around lakes, in swamps, and on areas that are subject to spring flooding. It’s best development is reached on a wet, well-drained, sandy or gravelly soil. It is readily distinguished from the Mountain or Downy alder by it’s stalked buds and triple-toothed leaves. The wood, although sometimes used for fuel-wood, has no commercial value. The tree does serve a useful purpose in checking the rush of water during spring floods.

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