Spring Lawn Care in the Pacific Northwest: A Simple Checklist

Lawns in the Seattle area face a different set of problems than lawns in most of the country. Our mild, wet winters and acidic soils are great for moss and tough on grass. The good news is that a few well-timed steps in spring make a big difference.

1. Clean up first

Start by clearing leaves, needles, branches, and anything else sitting on the grass. Debris blocks light and holds moisture against the lawn, which is exactly what moss loves.

2. Deal with the moss

Moss is a sign of conditions that favor it more than grass: shade, compacted soil, poor drainage, and acidic soil. Killing it without fixing those conditions means it comes right back. Treat it in early spring, rake out the dead moss once it turns brown or black, and then work on the conditions that let it grow.

3. Dethatch and aerate

Thatch is the layer of dead stems and roots between the grass and the soil. A thin layer is fine, but a thick one keeps water and nutrients from reaching the roots. Core aeration pulls small plugs of soil out of the lawn, which relieves compaction and lets air, water, and fertilizer get down where they're needed. In our clay-heavy soils, aeration is one of the most effective things you can do. Spring or early fall both work.

4. Check your soil pH

Many Western Washington soils lean acidic, which favors moss over grass. A simple soil test tells you whether your lawn would benefit from lime. If it does, it's an easy, inexpensive fix.

5. Overseed thin spots

A thick lawn is the best defense against moss and weeds. Overseed bare or thin areas with a seed blend suited to our climate, such as perennial ryegrass and fine fescues, with more fescue for shady areas. Seed does best once soil temperatures warm up in mid to late spring, or in early fall. Keep new seed consistently moist until it's established.

6. Fertilize at the right time

Feed the lawn once it's actively growing, typically in mid to late spring. A slow-release fertilizer gives steady growth without a big flush that needs constant mowing.

7. Mow high

Set your mower to keep grass around 2.5 to 3 inches tall. Taller grass shades out weeds and moss, develops deeper roots, and handles our dry summers better. Never take off more than about a third of the blade at once, and keep your mower blades sharp.