How to Grow Patmore Ash
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Patmore Ash
Fraxinus pennsylvanica 'Patmore'
treePatmore Ash is a hardy, deciduous cultivar of Green Ash prized for its exceptional cold tolerance and drought resistance. It grows into a medium-sized tree with a compact, oval crown and emerald-green compound leaves that turn golden-yellow in fall. This cultivar is particularly valued in northern climates where it thrives despite harsh winters and variable moisture conditions.
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Example Patmore Ash timeline · Pittsburgh, PA (Zone 6b)
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Plant Patmore Ash
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Patmore Ash
Late summer into fallBefore the first fall frost (≈ Nov 8)
Sample dates for Pittsburgh, PA. Sign up to get exact Patmore Ash dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Zones 2-5; exceptionally hardy for northern and prairie regions
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Young Sapling (Year 1-2)
2-3 yearsSmall tree with developing main trunk and early branching. Leaves are small and compound, growing in alternate arrangement.
Water consistently to establish deep root system. Stake if needed to encourage straight growth. Remove competing leaders. Apply 2-3 inch mulch ring.
Establishment Phase (Year 3-5)
3-5 yearsTree reaches 20-30 feet with increasingly dense branching and fuller canopy. Crown begins to take on characteristic oval shape.
Reduce watering frequency as roots deepen. Thin crowded branches for structure. Remove any dead or crossing branches. Begin formative pruning.
Mature Growth (Year 6-15)
10+ yearsFully formed tree 40-50 feet tall with dense, compact oval crown. Leaves are fully developed (8-12 inches long, compound leaflets).
Minimal pruning needed except for crossing or dead branches. Prune in late winter/early spring. Monitor for pests. Tree is fully drought tolerant.
Full Maturity (Year 15+)
IndefiniteEstablished shade tree reaching mature height of 40-50 feet. Dense canopy provides substantial shade. Fall foliage is prominent golden-yellow.
Maintenance pruning only. Remove lower branches to allow clearance if desired. No special watering needed. Tree may live 100+ years.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Monitor for D-shaped exit holes and canopy dieback. Use preventive insecticide treatments (imidacloprid) on young trees in at-risk areas. Remove and destroy heavily infested trees. This is the most serious threat to all ash species.
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Monitor for skeletonized leaves. Use horticultural oil sprays in spring or fall. Manage with insecticidal soap if severe. Usually not life-threatening.
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Galls are unsightly but cause minimal damage. Prune affected branches if desired. No treatment typically necessary.
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Borer larvae damage wood; borers attracted to stressed trees. Keep tree healthy with proper watering. Remove and destroy infested branches. Wrap young trunk to prevent egg-laying.
Uses
Shade Tree & Landscape Specimen
HouseholdPatmore Ash provides excellent shade in residential and commercial landscapes. Its compact, oval crown and moderate mature size (40-50 feet) make it ideal for properties where larger native ashes would be too large, and it casts dappled shade that allows underplanting. [source]
Wildlife Habitat & Food Source
WildlifeThe tree produces winged seeds (samaras) that wildlife consume, and its dense canopy provides nesting and shelter for birds and other wildlife. However, it is less preferred by some native insects than other ash species. [source]
Cold-Hardy Ornamental
HouseholdPatmore is specifically valued in northern climates and prairie regions (zones 2-5) where hardiness and drought tolerance are critical. Its golden fall color and disease resistance make it a reliable alternative to less hardy shade trees. [source]
Windbreak & Shelter Belt
HouseholdThe vigorous growth and hardy nature of Patmore Ash make it suitable for windbreak plantings and shelter belts in harsh northern climates, where it can help protect properties from wind and harsh weather. [source]
Harvest Tips
Not applicable—this is an ornamental/shade tree, not grown for harvest. Manage fallen seeds and leaves as desired. Seeds disperse naturally in autumn (winged samaras).
Fun Facts
- 🌱 Patmore Ash was specifically bred and selected in Canada for extreme cold hardiness, making it one of the few ash cultivars reliable in USDA zone 2.
- 🌱 The tree's compound leaves—arranged opposite one another on the stem—are a defining characteristic of ash trees and turn striking golden-yellow in fall.
- 🌱 While Patmore is more resistant to Emerald Ash Borer than some ash species, it is not immune; no ash species is fully resistant to this invasive pest.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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