SafePlants

Speckled Alder and Thinleaf Alder: An Overview

This page provides information about two closely related alders: speckled alder (Alnus incana subsp. rugosa) and thinleaf alder (Alnus incana subsp. tenuifolia, also sometimes referred to as Alnus tenuifolia). These plants are commonly found in North America and play significant roles in their respective ecosystems.

Considerations for Pets

• The text mentions that freshly harvested wood of thinleaf alder is considered hazardous. It would be important to prevent pets from chewing on freshly cut branches or consuming sawdust.

Nomenclature and Taxonomy

• Scientific Name: Alnus incana (grey alder or speckled alder) and Alnus incana subsp. tenuifolia (thinleaf alder)
• Common Names: Grey alder, speckled alder, mountain alder, thinleaf alder, river alder, thin-leaved alder.
• Family: Betulaceae (Birch Family)
• Synonyms: A. incana tenuifolia (Nutt.) Breitung, Alnus tenuifolia (Nutt.) Breitung.

Distribution and Habitat

• Speckled alder (A. incana subsp. rugosa) and thinleaf alder (A. incana subsp. tenuifolia) have overlapping but distinct distributions.
• Thinleaf alder is commonly found along western mountain streams and hillsides in the foothills. Its range extends from Tulare County in the Sierras to Alaska and into the Rocky Mountains. It's also found in northern New Mexico at moderate elevations (6500 to 8500 ft).
• It is also described as native to Colorado.
• It often grows directly along river edges and in mountain canyons with moist soils and swamps.
• Hardiness Zones: 1-7
• Forest Type: Western Mountain Streams

Morphological Characteristics

• Thinleaf alder ranges from a large shrub to a medium-sized tree, reaching up to 20 feet in height.
• It features red and golden pendent flowers (catkins) and green and gray foliage.
• It has persistent fruit that resembles tiny pinecones, as well as cone-like seeds in fall and winter.
• Leaves are oval, 2-4 inches long, with coarse, double-toothed edges.
• Mountain alder has smooth, gray-green to grayish bark and reddish bark.
• It is rhizomatous with associated fibrous roots.
• Foliage turns yellow in fall.

Ecological Role

• Thinleaf alder (Alnus incana ssp. tenuifolia) is a keystone nitrogen-fixer, playing a crucial role in riparian ecosystems.

Quirky Facts

• The wood of thin leaf alder was traditionally used to produce a red dye.
• It is known for its female catkins and persistent seeds, which resemble tiny pinecones.

Interactions with Other Organisms

• The plant may be interacted with by insects and other plants, though these interactions are not further explained in the provided text.

Additional Information

• Dave's Garden offers tips and ideas for gardens, along with seeds and plants.
• MountainNature.com serves as a field guide for identifying plants of western North America.