Pacific Northwest Lawn Care: What to Do, When, and Why

If you’re standing in your backyard in Oregon or Washington, staring at moss, patchy grass, and a forecast that can’t decide between drizzle or drought, you’re not alone. Folks around here want to know: What do I actually need to do for my lawn,and when,so I’m not wasting time or money?

Let’s get right to it. The Pacific Northwest lawn care schedule is different from anywhere else. You’ll deal with a long, cool growing season, months of summer drought, and winters that never freeze hard but stay soggy. If you want a decent lawn, you need to work with the climate, not against it.

Why the PNW Lawn Calendar Is Its Own Beast (opens in a new tab)

• Grass grows most of the year. You’ll mow in December, then again by February or March.
• From July to September, rain shuts off. Lawns without irrigation go brown and dormant.
• Winters are wet, not cold. Moss loves this. So do crane flies and fungal diseases.
• Soils are acidic (often pH 5.0-5.8). That’s why moss takes over and fertilizer doesn’t always work right.

Month-by-Month: What to Do and When (opens in a new tab)

January-February (opens in a new tab)

• Grass barely grows, but it’s not dead. Don’t let leaves or branches pile up,smothering is real.
• Stay off soggy turf. Foot traffic now means ruts and compaction later.
• Plan ahead: If you want pro aeration, get on their list now.
• Moss is everywhere, but don’t treat it yet. Wait until grass is actively growing.

March (opens in a new tab)

• Grass wakes up. Moss is glaringly obvious.
• Now’s the time for iron-based moss killer (not regular fertilizer). Wait for a dry spell, then apply. Rake out blackened moss after a week.
• First mow of the year: blade sharp, don’t scalp. Cut to 2-2.5 inches.
• Test soil pH. Only lime if you’re below 6.0.
• Light fertilizer (half-rate): 0.5 lb nitrogen per 1,000 sq ft.

April (opens in a new tab)

• Peak grass growth. Mow weekly, maybe more.
• Overseed bare or moss-cleared patches. Spring seeding works here, but fall is still better.
• Core aerate if soil is compacted and not waterlogged.
• Moderate fertilizer: 0.75-1 lb nitrogen per 1,000 sq ft.
• Crabgrass pre-emergent? Rarely needed in the PNW, but use only if you’ve had issues,and skip if you’re overseeding.

May (opens in a new tab)

• Still growing fast. Rain starts to fade.
• Raise mowing height to 2.5-3 inches as summer nears.
• Check irrigation system. Fix leaks, adjust heads, set timers.
• Spot-spray broadleaf weeds (dandelion, clover) if needed.

June (opens in a new tab)

• Rain gets unreliable. Watch for drought stress (wilting, blue-gray color).
• Start watering before lawn turns brown: 1-1.5 inches per week if you want green grass.
• Only fertilize if you’re irrigating. If not, skip it.
• Mow high. Taller grass shades roots and keeps soil cooler.

July-August (opens in a new tab)

• Hot and dry. You have two choices:
  • Irrigate: 1-1.5 inches of water per week, early morning, deep and infrequent.
  • Let it go dormant: Water just enough (0.5 inch every 2-3 weeks) to keep crowns alive. Don’t fertilize, don’t mow unless it’s getting shaggy.
• Don’t fertilize dormant or heat-stressed grass. You’ll burn it.
• Watch for crane fly larvae (spongy turf, sudden thinning).

September (opens in a new tab)

• The most important month for your lawn.
• Core aerate and overseed now. Warm soil, cool air, and returning rain make this the best window all year.
• Apply your main fertilizer: 1 lb nitrogen per 1,000 sq ft.
• Dormant lawns will green up on their own as rain returns.
• Resume regular mowing.

October (opens in a new tab)

• Still growing, just slower. Keep mowing as needed.
• Remove leaves promptly. Wet leaves = disease and dead patches.
• Late overseeding is possible if it’s mild, but don’t push it past mid-October.
• Only lime if soil test says so.

November (opens in a new tab)

• Growth slows, but doesn’t stop. Last fertilizer (0.5-1 lb N per 1,000 sq ft) to build roots for winter.
• Mow one last time at 2.5 inches.
• Clear all leaves before winter rains set in.
• Winterize irrigation (drain pipes, insulate backflow). Freezes are rare but not impossible.

December (opens in a new tab)

• Grass barely grows. Moss starts creeping back.
• Mow only if needed, and only when it’s dry enough.
• Keep debris off the lawn. Stay off saturated areas.

Moss: The PNW’s Never-Ending Battle (opens in a new tab)

Moss isn’t just a cosmetic problem. It’s a sign your grass is losing. Here’s what usually causes it,and what actually works to fix it: