The third week of September is a good time to seed or sod a new lawn or to renovate an older one. The most important time to fertilize a lawn in Western Washington is this month.
If you plan to feed your lawn only once a year, make it a fall feeding. Cooler weather encourages more root growth than top growth on your turf and winter rains can wash slow-release lawn food down deep into the root zone.
Then, when spring arrives, your well-fed lawn will be more likely to crowd out new weeds in the competition for space and sunlight.
Question. When is the best time to add lime to the lawn? My soil is very acid due to the amount of moss and buttercup I see competing with the lawn grasses. Should I wait until spring? B.P., Renton
Answer. Fall is a great time to apply lime to your lawn.
Garden centers offer several sources of lime to make soil less acid, and the best way to use each type of lime product will be written on the back of the bag. Follow the dosage instructions for best results.
If you have pets, use a pelleted lime that will not harm their foot pads.
Q. Can I add fertilizer and limestone on the same day to my lawn? H.G., Email
A. No. It is better if you don’t add fertilizer and lime at the same time.
Fertilize first, then wait until it rains or water in the fertilizer so that it will not react with the lime. Ammonia can be lost and phosphorus can become fixed (unavailable to the plants) if these elements combine with the lime.
Q. I am going to get a soil test done for my lawn and garden beds. What is the best pH goal for growing stuff? S.S., Tacoma
A. I am going to predict your soil test will show soil on the acid side of the soil range. Western Washington has heavy rainfall and this creates acid soil.
Most lawns, flowers and vegetables do best in soil that has a neutral or slightly acid pH. That would be the numbers between 7 and 6.5. When soil has a lower pH than this, plants can’t absorb enough phosphorus. In very acid soil, such as below 4.0, the tiny soil organisms and bacteria cease all activity — and not much but moss wants to grow.
Some shrubs, such as azaleas, rhododendrons, blueberries and camellias, do best in acid soils with a pH of 5.5 to 6.5, so be careful not to add lime around the base of these plants.
Q. Are wood ashes a good substitute for lime on the lawn? My neighbor says he uses wood ashes from his fire place to kill moss in his lawn. M.M., Enumclaw
A. Wood ashes do supply lime and some potassium to the soil, so perhaps your neighbor is on to something. The trick is spreading the ashes evenly over the lawn so they don’t fall in clumps and block sunlight.
Traditionally gardeners save their wood ashes for vegetable and flower beds and apply them as a light dusting in the fall so the winter rains can do the work of sweetening the soil.
Just know that lime and wood ashes work slowly to change soil acidity. If might take several years to see results.