American Elm
Ulmus americana
Active Threats to American Elm
Dutch Elm Disease
Fungal disease spread by bark beetles that has killed millions of elm trees across North America.
Signs to watch for:
- •Wilting and yellowing leaves in summer
- •Brown streaking in sapwood
- •Branch flagging (dead branches with leaves attached)
- •Rapid crown death
Recommended Action: Early detection is critical. Infected branches may be pruned to save the tree if caught early.
Free consultation available
Overview
Once dominant street tree, now rare due to Dutch Elm Disease. Surviving specimens are valued
American Elm lined streets throughout Ontario before DED devastated populations in mid-20th century. A few mature survivors remain as community treasures
Identification
Leaves
Oval leaves with distinctive asymmetric base and doubly serrated margins. Rough texture on upper surface.
Bark
Develops distinctive diamond pattern with interlacing ridges, alternating gray and brown layers.
Flowers
Small greenish-red flowers appear in early spring before leaves emerge.
Fruit
Flat, round, papery samaras with notched tips, maturing in late spring.
🦆 Valuable wildlife food source
Growing Conditions
Climate
Excellent adaptation to Eastern Ontario climate when disease-free
Hardiness Zones: 3, 4a, 4b, 5a, 5b
Light Requirements
Soil
Moisture: moist
Drainage: well-drained, moderate
pH Range: 5.5 - 8
Tolerance
Care & Maintenance
Pruning
Best Season: November-March
Frequency: Minimal once established
- Prune in November-March during dormant season only
- Never prune April-October (Dutch Elm Disease risk)
- Remove dead branches promptly
Avoid: Spring through fall when beetles are active
Watering
Establishment: Regular watering for first 2-3 years
Mature: Supplemental during drought
Seasonal Care Timeline
Spring
- Never prune - bark beetles emerging
- Monitor for DED symptoms
- Remove any dead elm wood from property
Summer
- Peak period for DED symptom development
- Watch for sudden wilting
- Contact arborist immediately if symptoms appear
Fall
- Assess tree health before winter
- Plan for dormant season pruning if needed
- Remove any dead branches
Winter
- Only safe season for pruning
- Inspect for bark beetle damage
- Remove dead wood when beetles dormant
Common Issues
Dutch Elm Disease
SevereFatal fungal disease spread by bark beetles
Symptoms: Wilting and yellowing leaves, Branch dieback, Brown streaking in sapwood
Treatment: Remove infected trees immediately to prevent spread
Prevention: Plant resistant cultivars, never prune in growing season, remove diseased trees
Professional arborist recommended
Elm Bark Beetle
SevereBeetle that spreads Dutch Elm Disease
Symptoms: Small holes in bark, Sawdust, Galleries under bark
Treatment: Remove infested wood immediately
Prevention: Maintain tree health, remove dead elms promptly
Professional arborist recommended
Quick Facts
When to Call an Arborist
Recommended inspection: Annual inspection critical, more frequent during growing season
- •Any signs of wilting or dieback
- •Bark beetle activity
- •Dead or dying branches
- •Suspect Dutch Elm Disease symptoms
- •Need for pruning (must be done dormant season)
Free consultation for Belleville residents
Recommended Services
Based on American Elm characteristics