Ash species
Fraxinus
Ash species (Fraxinus) is a tree suited to the Colorado Front Range, rated "Not Recommended" on the 2024 Front Range Tree Recommendation List. It matures to about 40–60 ft tall and 30–50 ft wide, fast-growing, needs medium water, and prefers full sun. Emerald ash borer is established in Colorado, so most Front Range cities now restrict or discourage planting new ash, and many ban it as a street tree. Existing trees can be kept if you treat them for the borer, at an ongoing cost, or they come down.
medium water40–60 ft tall and 30–50 ft wide
Photos
- Photo 1: no rights reserved
- Photo 2: (c) Nicholas A. Tonelli, some rights reserved (CC BY)
- Photo 3: (c) Keith Kanoti, Maine Forest Service, USA, some rights reserved (CC BY)
At a glance
Will it survive here?
- Hardiness zones
- USDA 3–9
- Water needs
- medium water
- Sun
- Best in full sun.
- Soil
- clay, loam, sandy
- Soil pH
- 6.0–8.2
- Hail tolerance
- moderate
- Wind tolerance
- moderate
- Salt tolerance
- moderate
How big, what shape?
- Mature size
- 40–60 ft tall and 30–50 ft wide
- Mature form
- Oval / upright
- Spacing / clearance
- ~50 ft of clearance
- Growth rate
- Fast
- Lifespan
- Medium
What it looks like, and when
- Fall color
- Purple, yellow
- Foliage
- Deciduous
Who else benefits
- Pollinator value
- low
- Deer
- Not deer-resistant
- Colorado native
- No
Site factors to consider
- Critical: Insects & DiseasesMain pressure here is Emerald ash borer, so keep it vigorous with steady water and a well-chosen site.
Common problems on the Front Range
- Emerald ash borer, lethal to all true ash; do not plant new ash where EAB is established
These are general tendencies for this group of plants on the Front Range, not a diagnosis. Many are stress-driven and preventable with good siting and watering. For a specific plant or an active problem, consult a certified arborist or your local CSU Extension office.
Frequently asked questions
- Is Ash species good for the Colorado Front Range?
- Yes, Ash species is a well-suited tree for Colorado's Front Range, rated "Not Recommended" on the 2024 Front Range Tree Recommendation List.
- Why is Ash species not recommended on the Front Range?
- The main catches here: Main pressure here is Emerald ash borer, so keep it vigorous with steady water and a well-chosen site.
- How big does Ash species get?
- It matures to about 40–60 ft tall and 30–50 ft wide.
- How much room does Ash species need?
- Give Ash species about 50 ft of clearance from buildings, fences, and other trees so the mature canopy isn't crowded.
- What shape does Ash species grow into?
- Ash species typically grows into an upright-oval crown, taller than it is wide. This is the species' usual mature form, named cultivars (columnar, weeping, or compact selections) can differ, so check the specific cultivar.
- Is Ash species hardy on the Front Range?
- Ash species is hardy in USDA 3–9. The Colorado Front Range spans roughly USDA 4b–6a, so it is well within range.
- How much water does Ash species need?
- It needs medium water once established.
- How fast does Ash species grow?
- Ash species is a fast-growing tree. Growth rate depends on water and site conditions on the Front Range.
- How long does Ash species live?
- Ash species has a moderate lifespan for a Front Range tree. Actual lifespan varies with site, water, and care.
- What color does Ash species turn in fall?
- Ash species turns purple and yellow in autumn. Fall color intensity varies with the season and site on the Front Range.
- Is Ash species native to Colorado?
- No. It is not a Colorado native, but it grows well on the Front Range.
- Is Ash species deer-resistant?
- No. Ash species is not considered deer-resistant and may need protection where deer browse.
- Is Ash species prone to pests or disease on the Front Range?
- Ash species can be affected by emerald ash borer. These are general tendencies, not a diagnosis, many are stress-driven and preventable with good siting and watering. For a specific plant or an active problem, consult a certified arborist or CSU Extension.
