Thinleaf/Mountain Alder
Alnus incana subsp. tenuifolia
Thinleaf/Mountain Alder (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
Photos
- Photo 1: (c) Jim Morefield, some rights reserved (CC BY)
- Photo 2: (c) Douglas Goldman, some rights reserved (CC BY-SA), uploaded by Douglas Goldman
At a glance
Will it survive here?
- Hardiness zones
- USDA 3–7
- Water needs
- medium to high water
- Sun
- Best in full sun.
- Soil
- clay, loam
- Soil pH
- 6.0–8.2
- Hail tolerance
- moderate
- Wind tolerance
- moderate
- Salt tolerance
- moderate
- Tolerates
- Rain gardens
How big, what shape?
- Mature size
- 20–30 ft tall and 15–20 ft wide
- Mature form
- Irregular / open
- Spacing / clearance
- ~20 ft of clearance
- Growth rate
- Fast
- Lifespan
- Medium
What it looks like, and when
- Foliage
- Deciduous
Who else benefits
- Pollinator value
- low
- Colorado native
- Yes
- Native ecoregion
- riparian, montane
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.
Frequently asked questions
- Is Thinleaf/Mountain Alder good for the Colorado Front Range?
- Yes, Thinleaf/Mountain Alder is a well-suited tree for Colorado's Front Range, rated "Recommended" on the 2024 Front Range Tree Recommendation List.
- How big does Thinleaf/Mountain Alder get?
- It matures to about 20–30 ft tall and 15–20 ft wide.
- How much room does Thinleaf/Mountain Alder need?
- Give Thinleaf/Mountain Alder about 20 ft of clearance from buildings, fences, and other trees so the mature canopy isn't crowded.
- What shape does Thinleaf/Mountain Alder grow into?
- Thinleaf/Mountain Alder 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 Thinleaf/Mountain Alder hardy on the Front Range?
- Thinleaf/Mountain Alder 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 Thinleaf/Mountain Alder need?
- It needs medium to high water once established.
- How fast does Thinleaf/Mountain Alder grow?
- Thinleaf/Mountain Alder is a fast-growing tree. Growth rate depends on water and site conditions on the Front Range.
- How long does Thinleaf/Mountain Alder live?
- Thinleaf/Mountain Alder has a moderate lifespan for a Front Range tree. Actual lifespan varies with site, water, and care.
- Is Thinleaf/Mountain Alder native to Colorado?
- Yes. It is a Colorado native.
