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Washington State University

Lawns – Tip Sheet #11

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A healthy, attractive lawn is possible without pesticides, wasting water or fertilizer run-off. The healthiest lawns start with good soil and full sun. For shady areas, slopes or near waterways, consider lawn alternatives such as native plants and ground covers.

Lawn Calendar

Let’s start with a basic lawn calendar for Western Washington.


  • If you did not do it at the end of last season, be sure to sharpen the mower blades or buy a new mower blade.
  • Mow regularly to about 2” to 3” and remove only 1/3 of grass length at each mowing – this encourages deeper roots, better drought and disease resistance, and helps crowd out weeds. Mow weekly in spring – cutting too much of the grass length at once stresses the grass. Mulch-mowing (leaving the grass clippings on the lawn) provides free fertilizer (nitrogen) and does not cause thatch build-up.
  • Fertilize in mid-May, if needed. If lawn is thin or yellow, apply ½ to 1 lb. of nitrogen per 1000 sq. ft. – read the label for application guidance. Have soil tested every few years to determine fertilizer and lime needs. Avoid “weed & feed” fertilizers and choose no-phosphorus fertilizers to protect our waterways. If you choose to use a pesticide/herbicide, be sure to read the label carefully and follow all warnings.
  • Don’t let weeds go to seed. If removing dandelions be sure to dig out the tap-root to prevent its return.
  • Improve thin areas – aerate, overseed and top-dress with about ¼” compost – April/May or September are the best times. New lawns should be seeded in spring, prior to Memorial Day or in fall, after Labor Day. Choose a lawn seed suited to the Pacific Northwest – a fine fescue and perennial ryegrass mix based on your sun conditions.


  • Mow as needed. Water deeply, about 1-inch per week – or let lawn go dormant. Water dormant lawn slowly and deeply once in July and once in August – and avoid heavy traffic.


  • Overseed and top-dress thin areas (September/October).
  • Remove weeds before they go to seed.
  • Fertilize as needed, using an organic fertilizer (September-October). A slow-release synthetic fertilizer can be applied as late as mid-November. Add lime if needed.


  • Don’t walk on frozen or water-soaked turf.
  • Have mower blades sharpened in preparation for spring.

Lawn Problems


Moss in lawns is generally a result of poor drainage, too much shade or acidic soil – often all three. While there are chemicals for moss control, without remedying the cause, the moss will simply return. Aeration will improve drainage and lime will reduce acidity. Alternatively, the moss can be left alone. Aerifying machines can be rented.


Some lawns develop thatch – a layer of old roots and stems – and if this layer becomes too thick the lawn will thin out. Soil that is compacted, low in organic matter or microorganisms is more susceptible. Thatch can be removed with a thatching rake or power thatcher. Power dethatching machines can be rented. Aeration will also help. The lawn will then need to be overseeded and top-dressed.

Lawn Care Resources

There are numerous local resources with more detailed advice on lawn care and renovation – all listed below are free.

WSU publications available at

  • Fine Fescue for Home Lawns, FS200E
  • Home Lawns, EB0482E
  • Phosphorus and Home Lawns, FS058E
  • Drought Tolerant Landscaping for Washington State, EM087E (Page 7-10)

WSU Hortsense at includes a “Lawn and Turf” section which covers over 30 lawn diseases and insect pests, including cultural, mechanical, biological and chemical control methods.

Saving Water Partnership: Natural Lawn Care at

Additional Master Gardener Tip Sheets, including “Gardening Websites” and “Gardening Publications” are available at Also see WSU’s “Gardening in Washington State” at and free downloads of WSU gardening publications at



Feature image by FOX.

CLH 2/8/24

WSU Extension Master Gardener Program * * * Extension programs and employment are available to all without discrimination. Evidence of noncompliance may be reported through your local Extension office.


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