Description: Thicket forming shrub or small tree, often with several trunks; forming a narrow crown of short, nearly horizontal branches, and with shiny yellow-green leaves, gummy when young.

Height: 9 m

Diameter: 20 cm

Leaves: 6-13 cm long; 4-7.5 cm wide. Ovate, shallowly wavy-lobed and doubly saw-toothed with long pointed teeth and 6-10 nearly straight parallel veins on each side; gummy or sticky when young. Shiny, speckled yellow-green on both surfaces, paler and often slightly hairy beneath, on stout petiole 1-2 cm long.

Shoots: Gummy, finely hairy, orange-brown and very glandular when young; becoming light grey, slender and slightly zigzag.

Bark: Grey to light grey, smooth and thin; inner bark red.

Flowers: Tiny; in spring, with or after leaves. Male flowers yellowish, drooping, narrowly cylindrical; in catkins 7.5-13 cm long, 10 mm wide. Female catkins enclosed during the winter, flowers reddish in narrow cones 10 mm long. The male catkins are bigger than our other Alders, and are very attractive in mid-April.

Cones: 12-20 mm long; three to six clustered on slender, spreading, long stalks; elliptical, with many hard, black scales; remaining attached. Tiny, elliptical, flat nutlets with two broad wings; maturing in summer.

Habitat: Along streams and lakes and in valleys. In California forms part of the Redwood Forest (m12), Douglas Fir Forest (m13), Yellow Pine Forest (m14) and Red Fir Dorest (m15) plant communities.

Range: SW and Central Alaska and Yukon, southeast to NW California and Central Montana. In Alaska to alpine zone above timberline; in NW California to 2150m.

In Alaska, Sitka Alder is a pioneer in disturbed areas following landslides, logging and glacial retreat. Adapted to soils too barren for other trees, this species improves soil conditions by adding organic matter and nitrogen from bacteria in its root nodules. It acts as a short-lived nurse tree for Sitka Spruce, later dying when shaded by the larger conifer. Introduced to Kew in 1903 by Prof. Sargent. Closely allied to Old World Alnus viridis.

Information: Audubon (1980), Bean I (1976)

Source: Stone Lane Gardens, Chagford, Devon - on the edge of Dartmoor. Seed from Harlow Carr (Northern Horticultural Society) seed list.

Purchased: 1993.11.05, Three specimens about 1.2m, provenance Sandpoint, Idaho.

Planted: 1993.11.07: two at southern end B4A and B5F; one in barn triangle A7E of US strip. A number from seed of trees growing at Harlow Carr Botanical garden (open pollinated) sown 1995.04.01, and planted at A6D 1998.09.29; B54H 1999.05.11; B56H 2001.05.19 and B55H 2001.05.20.

Progress: None of the Idaho trees has grown a great deal in height, though they do seem to have bushed up. All look healthy and have flowered and borne cones, though as yet no trial has been made to see if they are producing viable seed. On 2004.09.27 the tree at B4A is 2.4m, that at B5F 2.7m and the one at A7E is growing out rather than up, owing to shade from our crab apple tree, but is still near 3m. Two of the seedling trees have grown taller than the Idaho ones, at 3.3 and 3.6m.

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