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Alnus incana
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Gray Alder
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Alnus incana

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About Gray Alder (Alnus incana) Alnus incana (Grey or Speckled Alder) is a species in the Betulaceae (Birch) family with a wide range across the cooler parts of the Northern Hemisphere. In California it is found primarily in the Sierras. It is a small to medium size tree 15-20 meter tall with smooth grey bark even in old age, its life span being a maximum of 60-100 years. The leaves are matte green, ovoid, 5-11 centimeter long and 4-8 centimeter broad. The flowers are catkins, appearing early in spring before the leaves emerge, the male catkins pendulous and 5-10 centimeter long, the female catkins 1.5 centimeter long and one centimeter broad when mature in late autumn. The seeds are small, 1-2 millimeter long, and light brown with a narrow encircling wing. The Grey Alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range. The wood resembles that of the black alder, but is somewhat paler and of little commercial value.
Plant Description
Plant Type

Max. Height
15 - 70 ft (4.6 - 21.3 m)


Growth Rate

Winter Deciduous

Flower Color

Flowering Season

Native Status

Natural Setting
Site Type
Streams and other wet places in mountains up to 10,000 ft. elevation

Sun, Part Shade

Elevation ?
261' - 13977'

Annual Precip. ?
11.0" - 122.1"

Summer Precip. ?
0.18" - 4.10"

Coldest Month ?
10.0° F - 51.8° F

Hottest Month ?
33.4° F - 79.6° F

Humidity ?
0.33 vpd - 30.17 vpd

Soil Description
Tolerates a wide variety of soils and pH including sandy loam, chalky, rocky till, and nutrient-poor soils.

Fast, Medium, Slow

Cold Tolerance(° F)
Tolerates cold to -10° F

Landscaping Information
Water Requirement ?
Moderate - High
Extremely Low
Very Low
Moderate - High

Seldom Used

Max. Summer Water ?
Keep moist
No Summer Water
Keep moist

Common uses
Bird Gardens

Nursery Availability
Sometimes Available

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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