Alder, Thinleaf/Mountain
Alnus incana subsp. tenuifolia
Alder, Thinleaf/Mountain (Alnus incana subsp. tenuifolia) is a Colorado-native tree suited to the Colorado Front Range, rated "Recommended" on the 2024 Front Range Tree Recommendation List. It matures to about 20–30 ft tall and 15–20 ft wide, fast-growing, needs medium to high water, and prefers full sun. Leaf miner; leaf scorch in hot dry sites.
Colorado nativemedium to high water20–30 ft tall and 15–20 ft wide
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At a glance
- Rating
- Recommended
- Botanical name
- Alnus incana subsp. tenuifolia
- Variety / cultivar
- Thinleaf/Mountain
- Type
- Tree
- Mature size
- 20–30 ft tall and 15–20 ft wide
- Mature form
- Irregular / open
- Spacing / clearance
- ~20 ft of clearance
- Hardiness zones
- USDA 3–7
- Growth rate
- Fast
- Lifespan
- Medium
- Water needs
- medium to high water
- Sun
- Best in full sun.
- Colorado native
- Yes
- Foliage
- Deciduous
- Soil
- clay, loam
- Soil pH
- 6.0–8.2
- Hail tolerance
- moderate
- Wind tolerance
- moderate
- Salt tolerance
- moderate
- Pollinator value
- low
- Tolerates
- Rain gardens
Site factors to consider
- Critical: Cold HardinessThe average low suits it fine; our real cold risk is the swings, late frosts, and intense winter sun, so wrap young trunks and give it shelter.
- Watch: TransplantsIt resents being moved, so start with smaller stock, plant in spring, and get the spot right the first time.
Wildlife & ecology
- Pollinator value
- low
- Native ecoregion
- riparian, montane
Frequently asked questions
- Is Alder, Thinleaf/Mountain good for the Colorado Front Range?
- Yes, Alder, Thinleaf/Mountain is a well-suited tree for Colorado's Front Range, rated "Recommended" on the 2024 Front Range Tree Recommendation List.
- How big does Alder, Thinleaf/Mountain get?
- It matures to about 20–30 ft tall and 15–20 ft wide.
- How much room does Alder, Thinleaf/Mountain need?
- Give Alder, Thinleaf/Mountain about 20 ft of clearance from buildings, fences, and other trees so the mature canopy isn't crowded.
- What shape does Alder, Thinleaf/Mountain grow into?
- Alder, Thinleaf/Mountain typically grows into an irregular, picturesque outline that varies from plant to plant. This is the species' usual mature form, named cultivars (columnar, weeping, or compact selections) can differ, so check the specific cultivar.
- Is Alder, Thinleaf/Mountain hardy on the Front Range?
- Alder, Thinleaf/Mountain is hardy in USDA 3–7. The Colorado Front Range spans roughly USDA 4b–6a, so it is well within range. That said, it carries a cold-hardiness caution: The average low suits it fine; our real cold risk is the swings, late frosts, and intense winter sun, so wrap young trunks and give it shelter.
- How much water does Alder, Thinleaf/Mountain need?
- It needs medium to high water once established.
- How fast does Alder, Thinleaf/Mountain grow?
- Alder, Thinleaf/Mountain is a fast-growing tree. Growth rate depends on water and site conditions on the Front Range.
- How long does Alder, Thinleaf/Mountain live?
- Alder, Thinleaf/Mountain has a moderate lifespan for a Front Range tree. Actual lifespan varies with site, water, and care.
- Is Alder, Thinleaf/Mountain native to Colorado?
- Yes. It is a Colorado native.
