Diagnosing and Repairing Dead Spots in a Mature Ontario Lawn

Likely Causes

Dead patches in non‑traffic areas under a birch tree after 14 healthy years suggest fungal disease exacerbated by a wet year. Tree roots compete for water/nutrients, and shade increases humidity. The homeowner reports no insects.

Immediate Steps

1. Confirm diagnosis: Take a sample (grass + soil) in a sealed bag to a local nursery/garden center for identification.
2. Core aerate affected areas to relieve compaction and improve air/water movement.
3. Apply lime (50 lbs/1000 sq ft) if soil test indicates acidity.
4. Fertilize with Scotts Turf Builder (no weed control) per label.
5. Topdress with compost/humus, then overseed with a shade‑tolerant mix (fine fescues).
6. Keep seedbed moist until germination; then taper to deep weekly watering.

Seasonal Program

• Early spring (daffodil bloom): Lime + Scotts Halts (crabgrass preventer).
• Late spring: Scotts Turf Builder +2 (post‑emergent broadleaf control). Wet lawn first; no water 24–48 hrs.
• Fall: Aerate, lime, fertilize (Turf Builder), overseed shade mix.

Tree Management

Remove lower branches (to trunk) to increase light and air flow—reduces fungal pressure. Consult a pruning guide first.

Watering Rule

Water before 2 PM, not on rainy days. Deep, infrequent watering is best for established turf.