Pacific Northwest Lawn Care Month-by-Month (Western Valleys)

March Through May

  • Feed the wild birds. Attracting wild birds to your garden is an excellent way to naturally control harmful insects. Allow wild birds such as starlings to peck at your grass as they are feeding on insects that are harmful to your lawn.
  • Irrigation systems. Check your irrigation system well before the warm weather starts to ensure that there are no broken pipes, faulty sprinkler heads or broken risers. Check sprinkler heads for adequate coverage and adjust or replace as necessary. Check your timer to make sure it is functioning so that expensive water wastage does not occur. Have your irrigation backflow prevention device tested. In some cities, this a yearly requirement.
  • Get your mower ready. Perform mower maintenance.Take your mower into repair shop to perform annual engine maintenance and blade sharpening. Do it early in the season when the repair shops are not busy and to avoid the spring rush, so that you will not be delayed in mowing your grass in the spring.
  • Dethatch your lawn. Once your lawn has dried out and it is not excessively wet—usually in April or May—dethatch your lawn of old roots and stems. Rake and remove the thatch. Lawn dethatchers can be rented  or your gardener can perform this service.
  • Aerate compacted soil. Lawn soil becomes compacted due to human and pet traffic as well as rainfall thus hindering water and fertilizer penetration and the growth of grass roots. This is why it is wise to aerate your lawn occasionally—preferably annually—for the best looking and most healthy lawn. Lawn aerators can be rented or your gardener can perform this service.
  • Remove perennial weeds. Once the grass starts to grow and on a dry day, spot treat weeds with an herbicide. Read and follow all label directions including wearing the recommended personal protection equipment (or PPE) when applying chemicals herbicides. At any time of the year, you can dig out the weeds by hand.

April or May

  • Overseed bare spots. When the weather begins to warm up, but are not too hot and there is still regular rainfall, and when the grass begins to grow, it is an excellent time to overseed bare or thin spots in your yard. Fall is the best time of the year to reseed bare areas of your lawn, while spring is the second best time.
  • Start mowing. Begin to mow your grass every week or as needed. For the best results, do not remove more than one-third of the top growth of  your grass at a time. Grass can be kept shorter during cooler weather, but when the hot summer weather begins, it is less stressful on the grass to allow it to remain at about two to three inches tall. This also helps the grass to choke out any weeds that might try to grow up through it.
  • Weed control. Annual weeds, such as crabgrass, grow from seed each spring. A well-timed application of preemergence herbicide to stop them from growing is called for at this time of the year. A good guideline is to spread the preemergence herbicide as forsythia blooms in your area start to drop.
  • Fertilization. Feeding your lawn at least couple of times a year is a must. One fertilization in the spring and one again in the fall is the minimum requirement to maintain a healthy lawn. 


Lawn grubs. If lawn grubs are an issue in your lawn, prevent further damage by applying a grub-control product that continues to work throughout the season. The best time to do this is while doing lawn maintenance activities in early June.

July Through September

  • Summer lawn maintenance. Summer is about mowing, watering, and pest control. Stay on top of mowing for a healthy lawn.
  • Irrigation. Water deeply, slowly and as infrequently as possible. Try to avoid watering established lawns more than two or three times per week if possible except during extremely in hot conditions. It is not a bad idea to let the soil under your grass to dry out for a short time in between watering as this forces the grass roots to grow deeper in search of water thus making for a more drought tolerant lawn. It is best not to rely on timers for irrigation as temperatures will dictate water needs in addition to lack of rainfall. However, timers are helpful if you have lawns areas that are to large to micromanage or you will be gone for a period of time. 
  • Mowing. Mow once a week, removing no more than one-third of the height of the grass to avoid stressing it. Mow regularly to prevent weed seed spread.
  • Letting your lawn go dormant. If you want to save on your water bill during the summer months, you can skip watering your lawn if you don’t mind it turning brown. It is not dead; it is merely sleeping or in a dormant state. When the rains start up again in the fall, your lawn will turn green and start growing again. 


  • Weed control. Most perennial lawn weeds are more easily killed in the fall. Treat them with a broadleaf herbicide or pull them by hand.
  • Fertilization. If you only fertilize as part of your lawn maintenance once a year, fall is the best time to do it. In fact, your lawn will appreciate a light application of fertilizer in early autumn and again in late autumn.


  • Fertilization. When rains begin, fertilize with natural organic or slow release formulations. 
  • Lawn renovation. Late in the month, begin fall renovation including thatching and aerating if you were unable to do it in the spring. Rake and overseed bare spots, or install new seed or sod lawns.
  • Irrigation. As the cool weather begins, you can reduce the amount of lawn watering. Eventually, when the weather becomes cool enough and the fall rains start, you can stop watering and shut off  your irrigation system if you have one. Before winter, drain your irrigation system to prevent it from freezing.
  • Late-September Through Early November
  • Overseed bare spots. When the weather begins to cool down from the summer heat, yet while the grass is still growing, and the fall rains begin is an excellent time to overseed bare or thin spots in your yard. Fall is the best time of the year to reseed bare are of your lawn, while spring is the second best time.


  • Fertilization. Late in the month, apply winter fertilizer which is vital to maintain healthy turf. 
  • Mowing. Continuing mowing as needed while the grass is still growing if conditions are not excessively wet and cold.


  • Fertilization. Apply winter fertilizer if you forgot to fertilize your lawn the fall.  
  • Rake leaves. What more can be said about this?

December Through March

  • Perform mower maintenance. This is a good time to take your mower to repair shop for some annual engine maintenance and blade sharpening. Do it in the winter when the repair shops are not busy and to avoid the spring rush so that you will be ready to mow your grass in the spring.
  • Other lawn care. Avoid walking on extremely soggy or heavily frost-covered lawns to avoid damage to your grass.

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