Oregon Alder Alnus rubra
Other Common Name(s):
- Phonetic Spelling
- AL-nus ROO-brah
- Description
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Red alder is a deciduous tree in the Betulaceae (birch) family. It is native to the western coast of North America from Alaska down to California. This is one of the larger alders and grows 65-98 feet tall. It gets its name from the orange/red underbark that was used to make dye by Native Americans.
This tree can be distinguished from other alders by the rolled under margins of the leaves, the stalked buds and impressed veins on the underside of the leaves. Red Alder is able to grow in poor soils due to its association with the soil bacterium, Frankia, which allows it to fix nitrogen. Because of this, they are often used in land reclamation projects.
This tree grows fairly fast and will spread by seed. It tolerates soils ranging from well-drained gravels and sands to poorly drained clay or organic soils. It will grow in full sun to partial shade and prefers cool wet winters and warm dry summers.
Insects, Diseases, and Other Plant Problems: Red alder is fairly free from most insect and disease problems, especially when young (age 40 or 50) and uninjured. Phellinus igniarius, a white heart rot, is probably the major cause of cull in older trees. The forest tent caterpillar (Malacosoma disstria), western tent caterpillar (M. californicum), alder woolly sawfly (Eriocampa ovata), striped alder sawfly (Hemichroa crocea), the alder flea beetle (Altica ambiens), and a leaf beetle (Pyrrhalta punctipennis) have caused substantial damage but rarely kill the tree.
VIDEO created by Ryan Contreras for “Landscape Plant Materials I: Deciduous Hardwoods and Conifers or Landscape Plant Materials II: Spring Flowering Trees and Shrubs” a plant identification course offered by the Department of Horticulture at Oregon State University
- Profile Video:
- See this plant in the following landscape:
- Cultivars / Varieties:
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- Tags:
- Cultivars / Varieties:
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- Tags:
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Attributes:
- Genus:
- Alnus
- Species:
- rubra
- Family:
- Betulaceae
- Uses (Ethnobotany):
- A russet dye was made from the bark. Native Americans also used the bark to treat various illnesses. The wood is used for furniture and cabinets.
- Life Cycle:
- Woody
- Country Or Region Of Origin:
- Western North America
- Distribution:
- Alaska, Yukon, British Columbia, Washington, Oregon, California, Idaho and Montana
- Wildlife Value:
- Deer and elk will browse the twigs and finches will eat the seeds
- Play Value:
- Wildlife Cover/Habitat
- Wildlife Food Source
- Dimensions:
- Height: 66 ft. 0 in. - 98 ft. 0 in.
- Width: 35 ft. 0 in. - 50 ft. 0 in.
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Whole Plant Traits:
- Plant Type:
- Tree
- Woody Plant Leaf Characteristics:
- Deciduous
- Habit/Form:
- Conical
- Erect
- Growth Rate:
- Rapid
- Maintenance:
- Medium
- Texture:
- Medium
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Cultural Conditions:
- Light:
- Full sun (6 or more hours of direct sunlight a day)
- Partial Shade (Direct sunlight only part of the day, 2-6 hours)
- Soil Texture:
- Clay
- Loam (Silt)
- Sand
- Shallow Rocky
- Soil Drainage:
- Good Drainage
- Available Space To Plant:
- 24-60 feet
- USDA Plant Hardiness Zone:
- 5a, 5b, 6a, 6b
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Fruit:
- Fruit Color:
- Brown/Copper
- Fruit Type:
- Samara
- Fruit Length:
- < 1 inch
- Fruit Width:
- < 1 inch
- Fruit Description:
- Produces small brown cone-like strobiles less than an inch long that stay on the tree throughout winter. Seeds are winged samaras.
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Flowers:
- Flower Color:
- Red/Burgundy
- Flower Inflorescence:
- Insignificant
- Flower Bloom Time:
- Spring
- Flower Description:
- Male catkins are reddish and 4-6 inches long. Female catkins are cone-like and woody, oval
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Leaves:
- Woody Plant Leaf Characteristics:
- Deciduous
- Leaf Color:
- Green
- Deciduous Leaf Fall Color:
- Gold/Yellow
- Leaf Type:
- Simple
- Leaf Arrangement:
- Alternate
- Leaf Shape:
- Ovate
- Rhomboidal
- Leaf Margin:
- Serrate
- Hairs Present:
- Yes
- Leaf Length:
- 3-6 inches
- Leaf Width:
- 1-3 inches
- Leaf Description:
- 2.5-6 inch long green leaves are ovate with a pointed apex. The serrated margins are revolute or curled under and the veins are impressed especially on the undersides. Hairs are present on the undersides. They turn yellow in the fall.
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Bark:
- Bark Color:
- Light Gray
- Bark Description:
- The bark is mottled, ash-gray and smooth, often colonized by white lichen and moss. When bruised or scaped it has a rusty red color.
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Stem:
- Stem Color:
- Brown/Copper
- Green
- Stem Is Aromatic:
- No
- Stem Buds:
- Hairy
- Stem Bud Scales:
- Enclosed in 2 scales
- Stem Cross Section:
- Angular
- Stem Lenticels:
- Conspicuous
- Stem Description:
- Olive to reddish-brown twigs are triangular in cross-section, the buds are distinctly stalked and have 2-3 pubescent scales, lenticels are prominent.
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Landscape:
- Landscape Location:
- Lawn
- Riparian
- Landscape Theme:
- Water Garden
- Attracts:
- Small Mammals
- Songbirds
- Resistance To Challenges:
- Drought
- Humidity
- Poor Soil
- Wet Soil