Brown Patches After Cutting Overgrown Grass: Causes and Fixes

After a week-long delay in mowing, you cut very tall grass in Florida and now have brown patches that won’t recover. Two likely causes:

1. Scalping Shock

Removing more than 1/3 of the blade height at once exposes tender lower growth and roots to intense sun and heat, essentially “cooking” them. The grass may not recover if crowns were damaged.

2. Fungal Disease (Brown Patch)

Tall, wet grass creates a humid canopy ideal for Rhizoctonia (brown patch fungus). If patches are circular with a “smoke ring” edge, fungus is likely.

What to Do

• Rake out dead material to improve air flow.
• Apply a fungicide if brown patch is confirmed (consult local extension for diagnosis).
• Replant dead areas with plugs, seed, or sod.
• Mow regularly at the correct height—never remove more than 1/3 of the blade.

If the lawn was healthy enough to grow that tall, the soil is likely fine. Address the immediate cause and re-establish turf in dead zones.