Soil, Mulch, Compost & Fertilizer

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Build healthy soil with compost and mulch

Healthy soil holds more nutrients and water and will result in healthier plants. Improving your soil is the best way to save water and work in your lawn and garden. Learn about:

Quick tips

  • Know your soil. Look for thatch, compaction, or other soil problems you can fix.
  • Add compost. Dig or till 2-3 inches of compost into the soil when planting new garden beds or lawns. Every 2-3 years, spread another 1 inch on garden beds or ½ inch on lawns.
  • Use mulch. Spread 2-3 inches of fall leaves or grass clippings on beds in spring or fall. For woody plants and trees, use wood chips or coarse bark as mulch.
  • Fertilize responsibly. Trees and shrubs receive the nutrients they need from compost and mulch. For lawns, flowers, and gardens, look for the words “Natural organic” or “Slow-release” on fertilizer products to feed plants slowly, develop healthier roots, and reduce runoff to our streams and lakes.

More Information

Growing Healthy Soil guide (pdf)
Get to Know Your Soil (pdf)
Composting at Home guide (pdf)

Questions? Call the Garden Hotline at (206) 633-0224 or email

Links to Other Sites

Seattle Public Utilities’ Backyard Composting has extensive home composting information.

Soils for Salmon show landscape designers and builders how to protect and restore soil on construction sites, to meet Washington State’s requirements.

Backyard Composting