Dense turf is the first defence
A thick, correctly mown lawn shades the soil and leaves little room for weed seed. Scalping, thin patches and thatch problems all let weeds in. See mowing.
Timing (NC State)
- Pre-emergent for summer weeds such as crabgrass: mid-February to early March in North Carolina. Apply before soil warms, and water it in as the label says. Your date will shift with your climate.
- After plugging: use a pre-emergent that will not interfere with root growth.
- Post-emergent for broadleaf weeds in spring: only if broadleaf weeds are present, and wait three weeks after green-up.
- Summer: post-emergent only when weeds are present, the grass is actively growing and the lawn is not drought-stressed. Crabgrass, goosegrass, nutsedges, annual sedges and sandbur typically need two or three applications.
- Autumn: pre-emergent for winter annual broadleaves such as chickweed and henbit.
- Winter: broadleaf herbicides as needed for winter annuals.
Cautions
- Zoysia is sensitive to some herbicides. Use only products labelled for zoysiagrass and follow the label for rate and temperature limits.
- NC State warns never to spray glyphosate on dormant zoysia.
- Do not treat a stressed lawn.
- Keep herbicides off ornamentals and away from drainage.
Without chemicals
Hand-pull young weeds, raise the cut a notch, water deeply and rarely, and fill thin patches quickly. See patching bare spots.
When zoysia is the weed
Zoysia spreading into beds or other lawns is a different problem: see will zoysia take over other grasses.