Mountain Alder vs Water Arum - TreeTime.ca

Mountain Alder vs Water Arum

Alnus incana subsp. tenuifolia

Calla palustris

CUSTOM GROW

CUSTOM GROW

Mountain Alder
Water Arum

Mountain Alder is a native cold-hardy shrub or small tree often found along streams and in moist forested habitats. Its nitrogen-fixing ability enriches soils and supports surrounding vegetation, while its extensive root system helps stabilize streambanks and slopes. The fast growth rate allows it to establish quickly on disturbed sites, making it especially valuable in reclamation, restoration, and erosion control projects.

Often forming dense thickets, Mountain Alder enhances habitat quality in riparian and upland areas. It provides food and cover for various wildlife, including birds and small mammals. Recognized as an important species for soil and water conservation, it is well suited for riparian planting, naturalization, and ecological restoration.

Note: We use Sitka Alder for Alnus incana subsp. tenuifolia. This species is also known by many other common names, including Grey Alder, River Alder, and others. Please confirm the scientific name to ensure you are ordering the correct plant.

Water Arum is a native perennial wetland plant known for its showy white oval sheaths (spathe) that surround a yellow-green, cylindrical flower spike (spadix). It has large, oblong, heart-shaped leaves on stems that rise above the water from shallow, spreading rhizomes. The blossoms are followed in late summer by tiny, pear-shaped fruits that ripen to bright red, adding ornamental interest to wet habitats.

Water Arum provides food for birds and small mammals that eat its berries, and its flowers attract pollinators. It can tolerate cold climates and forms colonies in shallow water and saturated soils. It is well-suited for ecological restoration, riparian planting, naturalisation, and habitat projects in wet and shaded environments.

Mountain Alder Quick Facts

Water Arum Quick Facts

Zone: 1a
Zone: 1b
Height: 6 m (20 ft)
Height: 0.2 m (0.8 ft)
Spread: 3 m (10 ft)
Spread: 0.2 m (0.8 ft)
Light: partial shade, full sun
Light: shade, partial shade
Moisture: normal, wet
Moisture: wet
Growth rate: medium
Growth rate: medium
Life span: medium
Life span: short
Growth form: multi-stemmed, thicket-forming
Growth form: colony-forming
Spreading: rhizomes - medium, seeds - low, layering - low
Spreading: rhizomes - medium, seeds - low


Toxicity: toxic if ingested
Bark: smooth, gray to brown
Flowers: white sheath around and yellow spike
Bloom time: spring to summer
Berries: red, in clusters
Hybrid: no
Hybrid: no
Catkins: yes
Catkins: no


Native to: AB, BC, SK, YT, NT
Native to: AB, BC, SK, MB, ON, QC, NS, NB, NL, YT, NT, PE
Other Names: river alder, speckled alder, thin-leaved alder, thinleaf alder, western river alder
Other Names: bog arum, swamp lily, wild calla, wild dragon