Seasonal timing
Right now, in summer, the lawn is holding — mow high, water deep, and scout for the summer annuals before they seed. The whole yard runs on timing: the same job — a pre-emergent, a mow, a feed — either works or does nothing depending on when you do it. Below is the year for a cool-season lawn, and where each weed entry's window falls in it.
You're in the heat. This is a holding season, not a renovation one — the wins are defensive. Mow high (3.5–4") so tall turf shades out germinating weeds, water deep and infrequent to drive roots down, and mark the summer annuals now (lespedeza in thin sunny spots, stiltgrass in damp shade) so you're ready for the knock-back window as their flower spikes form. Hold the nitrogen — the feed that builds the lawn is the fall one. Full year below.
Plants keep better time than the calendar. Three cues carry most of this page: forsythia in bloom (soil ~55 °F — the pre-emergent window), flower spikes forming on summer weeds (last call to cut before seed drops), and first frost (summer annuals die on their own). Watch the yard, not the month.
Summer
- Mow high — 3.5 to 4 inches.The single best summer defence. Tall turf out-competes ground-huggers like lespedeza and shades out germinating weeds.
- Water deep and infrequent.Drives roots down and avoids the shallow, weak turf that shallow daily watering breeds.
- Scout for the summer annuals.Lespedeza in thin, sunny, compacted spots; stiltgrass in shady, damp edges. Mark them for the knock-back window next.
Late summer
- Kill the summer annuals before they seed.This is the window both weed entries hinge on — late July into September, before seed sets. Lespedeza: triclopyr + mow higher + feed nitrogen. Stiltgrass: pull, or mow low mid-to-late August, or grass-selective spot-spray. One year's seed is next year's crop.
- Plan the fall renovation.Line up aerator, seed and fertiliser now so early-fall's short window isn't wasted.
Early fall
- Core aerate.Relieves the compaction that lespedeza and stiltgrass exploit. The most valuable single thing you do for the lawn all year.
- Overseed thin spots.Cool-season grass establishes best now — warm soil, cool air, low weed pressure. Aerate first, then seed into the holes.
- Main nitrogen feed.Fall feeding builds roots and next spring's density. This is the most important feed of the year — and it tips the balance away from nitrogen-fixing weeds like lespedeza.
Fall
- Keep mowing until growth stops; drop the height slightly on the last cut.Long grass matted under snow invites disease.
- Stay ahead of the leaves.A thick leaf layer smothers turf and the new seedlings. Mulch-mow or clear.
Winter
- Stay off frozen and frosted turf.Footprints on frosted grass bruise the crowns and show for weeks.
- Service the mower · sharpen the blade · plan.A sharp blade cuts clean; a dull one shreds and stresses the grass all season.
Early spring
- Pre-emergent down — before anything germinates.Crabgrass, stiltgrass and lespedeza all sprout early. A pre-emergent (
prodiamine/dithiopyr) at forsythia bloom stops the whole summer-annual crop in one pass — the highest-leverage move of the year. - First cleanup + first mows.Clear winter debris, tune the mower, start cutting as growth resumes. Light touch — the turf is still waking up.
Late spring
- Spot-treat broadleaf weeds.They take herbicide best while growing hard and before summer heat. Dandelion, plantain, clover — hit them now on a dry day.
- Raise the mowing height as heat builds.Taller grass shades the soil, holds moisture, and denies low weeds a foothold going into summer.
- Go light on nitrogen.A heavy spring feed pushes soft, disease-prone growth. Save the real feeding for fall (below).
Two timing conflicts to know
The mistakes that come from doing the right thing in the wrong month.