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
Continue at Premium Grass Seeds
Build the fall window before it opens.
Use the calendar for timing, then move through the three buying decisions in order. Start with the zone-filtered seed comparison, then use the matching starter and equipment guides. The seed comparison stays anchored to Zone 4b.
1 · Seed
Compare zone-fit fall seed
Start with overseeding options that list this zone, then confirm the local establishment window.
Open: Compare zone-fit fall seed → (opens in a new tab)2 · Starter
Pair the starter fertilizer
Pick the establishment feed after the seed; it is not a substitute for it.
Open: Pair the starter fertilizer → (opens in a new tab)3 · Equipment
Stage the overseeding tools
Choose the spreader, prep, and watering gear before the window opens.
Open: Stage the overseeding tools → (opens in a new tab)
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