Spring lawn and moss checklist

Fix the cause first

WSU's Master Gardeners say moss most often comes from poor drainage, too much shade or acid soil, and that it comes back unless you fix the cause. Aeration helps drainage and lime lowers acidity. You can also leave it alone. (WSU Extension) If you do treat it, the Pacific Northwest handbook says to rake it out and use iron (ferrous sulfate) on damp moss while it is growing; it stains sidewalks and driveways for good, and copper products are no longer recommended. (PNW Handbooks)

Who may treat it for pay

• Moss control, weed-and-feed and spot sprays all count as pesticide use. (WSDA)
• A crew that applies any of them for pay, even once, needs a WSDA commercial applicator license; moss on lawns falls under the Structural and Turf Demossing category. (WSDA) (WSDA categories)
• The application fee for that license is $250. (WSDA, read Oct 18, 2026) Workers who apply it for the company need their own commercial operator license. (WSDA) (RCW 17.21.110)
• If they don't have one, WSDA says they can get licensed, subcontract the spraying to a licensed company, or stop offering it. Ask which they do. (WSDA)
• After a treatment, a licensed applicator must put a marker at the usual way into the yard, with the company name and phone number on it. A fenced backyard needs none. (RCW 17.21.410)

Details: weed and moss treatment licensing.

Mowing and cleanup

Lawn care needs no L&I contractor registration, so a mowing crew doesn't need a contractor number. (L&I F625-084-000) Do ask for a state business license if they earn $12,000 a year or more. (WA DOR, read Oct 17, 2026) In Seattle, gardeners for private homes are covered by the Domestic Workers Ordinance. (Seattle) More: how to compare lawn care quotes.

Sprinklers

• Installing a home lawn sprinkler system is landscaping work under L&I's contractor rules, so that crew should be registered. (WAC 296-200A-016)
• In Olympia, a yard sprinkler system needs a permit. (Olympia)
• Saving Water Partnership utilities pay up to $100, $10 per working zone, to replace an old timer with a WaterSense timer bought between April 1 and October 31. Apply within 30 days. (Saving Water Partnership, read Oct 18, 2026)

Bigger spring projects

• Seattle: retaining walls up to 4 feet, fences under 8 feet with no concrete or masonry over 6 feet, and patios under 18 inches above grade need no permit in most cases. (Seattle SDCI)
• Tacoma: landscaping on already developed land is exempt outside critical areas, but moving more than 50 cubic yards of soil, or adding 2,000 square feet of hard surface, needs a site development permit. (Tacoma)
• Unincorporated King County: excavation or fill over 100 cubic yards, or more than 2,000 square feet of new impervious surface, needs a permit. (King County)

Patios and walls are landscape construction, so check the registration on L&I Verify. (L&I)