Spring Lawn Care in London, ON
Current SeasonSpring in London begins in April as winter's grip loosens and temperatures climb above freezing. Ontario's Great Lakes moderate the climate, giving London an earlier spring than Prairie cities but later than coastal BC. Soil temperatures reach the critical 10°C mark by late April in southern Ontario.
April reveals winter damage — snow mould patches, vole tunnels, and ice sheet damage. By mid-April in London, the lawn begins to show green growth. May brings rapid improvement as temperatures rise steadily. This is the busiest spring lawn care period in Ontario.
Kentucky Bluegrass is the dominant lawn grass in London's Great Lakes climate. It breaks dormancy in April and enters active growth by May. Perennial Ryegrass greens up fastest, Fine Fescue follows, and KBG fills in last but thickest. Tall Fescue maintains some green through winter in milder Ontario locations.
Spring priorities in London: assess and repair winter damage in April; apply first fertiliser in late April when soil reaches 10°C; apply crabgrass pre-emergent when forsythia blooms; and overseed bare patches in May while spring rains support germination.
Ontario's pesticide ban restricts cosmetic use of many lawn chemicals. Focus on cultural practices — proper mowing height, overseeding, and fertilising — as the primary weed defence in London.
Great Lakes & Ontario Zone — Spring Overview
April green-up. Snow mould treatment first. Fertilise in late April–May. Overseed thin areas in May. Crabgrass pre-emergent when forsythia blooms.
Spring Tasks for London
1. Assess winter damage in April
Walk the lawn in April looking for: snow mould patches, vole damage (surface tunnels), ice sheet damage (matted dead grass), and winter kill in exposed areas. Rake all affected areas to allow air circulation.
2. Fertilise in late April
Apply the first fertiliser when soil temperature reaches 10°C — usually late April in Toronto and Hamilton, mid-May in Ottawa. Use a slow-release nitrogen formula. Avoid liquid fertiliser early in spring when soil is still cold.
3. Apply crabgrass pre-emergent
Apply when forsythia finishes blooming in Ontario — a reliable indicator that soil temperature is approaching 12°C at 5cm depth. One application protects all season.
4. Overseed thin areas in May
Mid-May is Ontario's best spring overseed window — soil is warm and spring rains support germination. Use a Kentucky Bluegrass and Ryegrass blend. Keep seed moist for 14–21 days until established.
5. Dethatch if thatch exceeds 20mm
Power rake or scarify in late April if thatch layer is over 20mm thick. Follow immediately with overseeding and fertiliser. Only dethatch when lawn is actively growing.
Best Grasses for London in Spring
Frequently Asked Questions
When does the lawn green up in London, ON in spring?
In London, ON, lawns typically begin to green up when soil temperature consistently exceeds 10°C. This happens in late April in southern Ontario, mid-May on the Prairies, and as early as February–March in coastal BC. Watch for the first signs of new growth before beginning spring lawn work.
How do I treat snow mould in London?
Snow mould appears as matted grey or pink patches after snow melts in London, ON. Rake affected areas firmly to break up the mats and allow air circulation. Most cases recover naturally without fungicide. Prevent snow mould next year by cutting lawn to 60mm before winter, removing all leaves, and avoiding large snow piles on the lawn.
When should I apply the first fertiliser in spring in London?
Apply the first spring fertiliser in London, ON once soil temperature reaches 10°C — this is when grass begins active growth. Use a slow-release high-nitrogen formula. Applying to cold soil wastes fertiliser and may promote disease. A soil thermometer at 5cm depth gives the most accurate reading.
Should I dethatch my lawn in spring in London?
Dethatch in London, ON in late spring if the thatch layer exceeds 20mm. Power rake or scarify when the lawn is actively growing — never when dormant or stressed. Follow dethatching immediately with overseeding and fertiliser to help the lawn recover quickly.
When should I apply crabgrass pre-emergent in London?
Apply crabgrass pre-emergent in London, ON when soil temperature reaches 12°C at 5cm depth. In Ontario, this coincides with forsythia finishing bloom. In Quebec, watch for lilac bloom. Apply before crabgrass germinates — once you see crabgrass, pre-emergent is too late.