Zone 4a Club · Lawn Calendar
Zone 4a Lawn Calendar
Year-round timing tuned to Zone 4a's climate window.
Winter low
-30°F
Last frost
May 15
First frost
Sep 25
Season
130d
Primary Overseeding Window
Aug 25 → Sep 20
The single highest-leverage window for cool-season seed in Zone 4a.
Quarter
Spring in Zone 4a
- ▪Mid-May: overseed winter damage; KBG primary
- ▪First mow at 4 inches; maintain 3 inches
- ▪Apply 0.75 lb N/1000 sqft in late May
- ▪Pre-emergent crabgrass at soil temp 55°F
Quarter
Summer in Zone 4a
- ▪Mow at 3–3.5 inches
- ▪1" water per week; deep + infrequent
- ▪Skip July fert on non-irrigated lawns
- ▪Watch for summer patch on KBG-heavy lawns under stress
Quarter
Fall in Zone 4a
- ▪Primary overseeding window: Aug 25 – Sep 20
- ▪Apply 1 lb N/1000 sqft late August (the year's biggest fert)
- ▪Aerate and overseed compacted areas
- ▪Final mow at 2.5 inches by late October
Quarter
Winter in Zone 4a
- ▪Lawn dormant Nov–April
- ▪Avoid frozen turf traffic
- ▪Plan spring purchases in February
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