Fall Important Time to Fertilize Your Lawn


My lawn is looking worse than normal for this time of year. I don’t usually fertilize until October. Would it help to fertilize sooner this year?

I normally fertilize my lawn just twice a year. I consider the fall application more important than the spring application. Anytime from now until the end of November is effective. You will see a quicker response if you apply it sooner.

Fall lawn fertilization keeps the grass green all winter and into early spring. It allows you to wait until May to apply a spring fertilization. Then the spring application lasts through the summer.

Washington law now excludes phosphorus from lawn fertilizers in order to reduce the amount of phosphorus leaching into above ground and below ground water supplies.  I now recommend a 3-0-2 balance of nitrogen-phosphorus-potassium. A typical formulation would be 15-0-10 or 18-0-12. An organic lawn fertilizer would be more like 9-0-6. The numbers do not have to be exact, but approximately in this ratio.

I like to have at least 1/3 of the nitrogen in a slow release form since nitrogen is very soluble and some leaches quickly below the grass roots. The most effective slow release mechanism is coating or encapsulating some of the nitrogen with sulfur or a poly coating. There are also chemical nitrogen compounds such as methylineurea which are slow release. Check the “guaranteed analysis” to see if some of the nitrogen is slow release. The analysis label will also list iron, which is also helpful, even in small amounts.

Special lawn fertilizer formulations for fall application (usually called “winterizer” blends) are also suitable. However, I usually apply the same fertilizer in both fall and spring.

If you use a liquid application yourself or have one applied by a lawn care company, make an application now and another one in late October. Liquid fertilizers do not last as long as granular fertilizer. They are satisfactory as long as they are applied more often.

If you have broad leaf weeds in you lawn, a weed and feed product is a convenient way to apply both fertilizer and weed killer at the same time.

I can apply lawn fertilizer or weed and feed for you for a reasonable cost.


Allen Wilson

Allen has been writing about gardening for over 30 years. He is a retired professor of Horticulture.

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