Lumpy Lawn? It Might Be Earthworms—Why That's Good and How to Smooth It Naturally

Hard, lumpy mounds across your Eastern Washington lawn aren't from grubs—they're likely earthworm castings. And that's a good sign.

Earthworms: Nature's Aerators

Earthworms consume thatch and organic matter, excreting nutrient-rich castings that create small mounds. They aerate soil, cycle nutrients, and improve structure. Colorado and Washington are known for active earthworm populations—bumpy lawns are normal there.

Smoothing the Surface

• Core aerate in spring or fall to relieve compaction.
• Roll with a water-filled lawn roller after aeration (when soil is moist but not wet) to flatten castings.
• Mow high (3.5–4 inches) to support deep roots and earthworm habitat.

Keep the Clover

That spreading clover? It's a nitrogen-fixing legume—free fertilizer. It feeds bees, stays green in drought, and crowds out weeds. Microclover varieties blend seamlessly with turf.

Don't fight earthworms or clover. Manage the lumps mechanically and enjoy the free soil building.