Zone 4b Club · Lawn Calendar
Zone 4b Lawn Calendar
Year-round timing tuned to Zone 4b's climate window.
Winter low
-25°F
Last frost
May 10
First frost
Sep 30
Season
140d
Primary Overseeding Window
Aug 25 → Sep 25
The single highest-leverage window for cool-season seed in Zone 4b.
Quarter
Spring in Zone 4b
- ▪Mid-May: overseed winter damage
- ▪First mow at 4 inches; maintain 3 inches
- ▪0.75 lb N/1000 sqft late May
- ▪Pre-emergent crabgrass at soil temp 55°F (mid-May)
Quarter
Summer in Zone 4b
- ▪Mow at 3–3.5 inches
- ▪1" water per week; deep + infrequent
- ▪Skip July fert on non-irrigated lawns
- ▪Monitor summer patch on KBG monocultures
Quarter
Fall in Zone 4b
- ▪Primary overseeding: Aug 25 – Sep 25
- ▪1 lb N/1000 sqft late August (biggest fert of year)
- ▪Aerate compacted areas
- ▪Final mow at 2.5 inches mid-late October
Quarter
Winter in Zone 4b
- ▪Dormant Nov–April
- ▪Avoid frozen-turf traffic
- ▪Plan spring purchases in February
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