Why Summer Fertilizer Harms Portland Lawns and How to Treat Brown Patches

Don't Use SummerGuard in Portland

Cool-season grasses (fescue, rye, bluegrass) should never be fertilized in summer. SummerGuard adds nitrogen and insecticides—both counterproductive.

Why Summer Feeding Damages Grass

• In heat, cool-season grasses cannot convert fertilizer into energy.
• Forced growth depletes stored reserves, weakening the plant.
• Fall fertilization builds energy storage for next year.

Brown Patch Causes

• Heat dormancy: Some grass varieties brown naturally in high temperatures.
• Fungal disease: Hot, humid conditions trigger brown patch (Rhizoctonia).
• Insects: Rarely the primary cause; identify before treating.

Correct Approach

1. Fertilize only in late spring, early fall, late fall.
2. If insects are confirmed, spot-treat with a targeted spray—no fertilizer combos.
3. Accept summer browning as natural dormancy; grass recovers in fall.