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ALNUS rubra

Image of Alnus rubra

Jesse Saylor

Family

Betulaceae

Botanical Name

ALNUS rubra

Plant Common Name

Oregon Alder, Red Alder

Special Notice

This entry has yet to be reviewed and approved by L2G editors.

General Description

Glossy dark green leaves with red veins, platy gray bark and the persistent brown seed fruits make red alder a great shade tree with beauty and landscape adaptability, including salty soil. Native to extreme western Canada southward into Oregon and California in the United States, it's a vigorous, cone-chaped deciduous tree. Its bark becomes ghostly gray-sandy brown that cracks into flat plates. The inner bark will turn red when exposed to air.

In early spring this tree flowers before leaves emerge. The male flowers are in drooping, finger-like clusters called catkins and are coral and yellow. The female flowers are small and red and occur at twig tips. After wind pollination, the green cylindrical fruits form and ripen to brown before shedding the seeds. The dried fruits persist on the branches into fall and winter. No notable fall leaf coloration occurs on the oval leaves that are dark green with reddish veins. The leaf edges are bluntly toothed and often recurve.

Grow red alder in average garden soils that are moist to wet, or average well-draining. It is adaptable to acidic and alkaline soils as long as it is fertile and can tolerant brackish water and saline ground. This species is fast growing and also works well as a windbreak in addition to being a specimen shade tree for park or avenue. It will form groves along water features if not managed. This species is particularly susceptible to tent catepillar damage in many parts of the American Northwest.

Characteristics

  • AHS Heat Zone

    7 - 1

  • USDA Hardiness Zone

    4 - 7

  • Sunset Zone

    3a, 3b, 4, 5, 6, 7, 14, 15, 16, 17

  • Plant Type

    Tree

  • Sun Exposure

    Full Sun, Partial Sun, Partial Shade

  • Height

    45'-75' / 13.7m - 22.9m

  • Width

    20'-30' / 6.1m - 9.1m

  • Bloom Time

    Early Spring

  • Native To

    North America, United States, Northwestern United States, Alaska, California, Canada

Growing Conditions

  • Soil pH

    Acidic, Neutral, Alkaline

  • Soil Drainage

    Average

  • Soil type

    Loam, Sand

  • Tolerances

    Wet Site, Drought, Salt

  • Growth Rate

    Fast

  • Water Requirements

    Drought Tolerant, Average Water

  • Habit

    Pyramidal

  • Seasonal Interest

    Spring, Summer, Fall

Ornamental Features

  • Flower Interest

    Insignificant

  • Flower Color

    Yellow, Red, Coral

  • Fruit Color

    Brown

  • Foliage Color (Spring)

    Green, Dark Green

  • Foliage Color (Summer)

    Dark Green

  • Foliage Color (Fall)

    Dark Green

  • Bark Color

    White, Sandy Brown, Gray

  • Fragrant Flowers

    No

  • Fragrant Fruit

    No

  • Fragrant Foliage

    No

  • Bark or Stem Fragrant

    No

  • Repeat Bloomer

    No

  • Showy Fruit

    Yes

  • Edible Fruit

    No

  • Showy Foliage

    Yes

  • Foliage Texture

    Medium

  • Foliage Sheen

    Glossy

  • Evergreen

    No

  • Showy Bark

    Yes

Special Characteristics

  • Bark Texture

    Platy

  • Usage

    Screening / Wind Break, Shade Trees

  • Sharp or Has Thorns

    No

  • Invasive

    No

  • Self-Sowing

    Yes