Crabgrass Winnipeg: How to Identify, Prevent, and Control This Summer Invader
⚡ Quick Takeaways
- Crabgrass dies each fall but drops up to 150,000 seeds per plant first
- Seeds germinate when soil hits 55°F (13°C) for 4-5 days—typically late May in Winnipeg
- A thick lawn mowed at 3 inches or higher is your best defense
- Pre-emergent timing is critical: apply before forsythia blooms
- Effective control takes 2-3 seasons of consistent effort
What Is Crabgrass and Why Is It in My Winnipeg Lawn?
That light green, sprawling grass ruining your lawn’s uniform look? Probably crabgrass. This annual weed thrives precisely when your cool-season lawn grasses struggle most. While Kentucky bluegrass slows down during hot summer, crabgrass kicks into high gear.
How to Identify Crabgrass
Crabgrass stands out with its light green colour, sometimes with yellowish tint. The texture is coarser with wider blades. Two species commonly appear: large crabgrass (hairy) and smooth crabgrass (stays lower).
- Light green to yellowish color
- Coarse, wide blades
- Sprawling crab-leg growth pattern
- Finger-like seed heads mid-summer
- Reddish-purple tinge in fall
When Does Crabgrass Germinate in Winnipeg?
Crabgrass seeds begin germinating when soil temperatures reach approximately 55°F (13°C) for 4-5 consecutive days. In Winnipeg, this typically occurs in late May.
The traditional indicator is forsythia bloom. When those bright yellow flowers appear, soil temperatures are approaching germination range.
How Do I Prevent Crabgrass from Taking Over?
Cultural Controls: Mowing, Watering, and Lawn Density
- Mow high: Keep lawn at 3 inches or taller to shade soil surface
- Water deeply: Deep watering (6-8 inches) once or twice weekly
- Overseed thin areas: Fill bare patches in late summer/early fall
- Reduce compaction: Annual core aeration improves soil structure
Pre-Emergent Herbicide Timing
Pre-emergent herbicides create a chemical barrier that kills crabgrass seedlings as they germinate. For Winnipeg, target application when soil temperatures approach 50-55°F—typically mid-May, when forsythia is in full bloom.
Important: Pre-emergent herbicides prevent ALL seeds from germinating, including grass seed. If you’re planning to overseed, you cannot use pre-emergent in that area.
Why Does Crabgrass Keep Coming Back Every Year?
A single mature crabgrass plant can produce up to 150,000 seeds in one season. Those seeds remain viable for years—some research suggests 15 years or more in soil.
Effective management requires a multi-year control strategy:
- Year one: Focus on preventing seed production
- Year two: Apply pre-emergent, continue mowing, overseed thin areas
- Year three and beyond: Maintain practices, populations gradually decrease
Professional Crabgrass Control
At Lawn N Order, our lawn care programs combine proper timing, professional-grade products, and cultural recommendations tailored to Manitoba’s climate.
Get a ConsultationLearn more about spring lawn care and professional lawn services.
