After years of struggling to remember exactly when lawn fertilizer should be applied, WSU Extension turfgrass scientists have come to the rescue of lawn aficionados throughout Western Washington.

According to Dr. Gwen Stahnke, one of WSU's turfgrass scientists, it works out that the correct time to fertilize the lawn just happens to coincide with four important holidays - Easter, Memorial Day, Labor Day and Thanksgiving. Fertilizing within a week of these dates will keep turf healthy which at the same time, helps reduce damage from feeding by European crane fly and helps to reduce moss invasion. If you have been fertilizing your lawn and returning clippings, you can most likely back off on at least one of your spring applications due to the nutrients you are putting into the soil via the decomposition of the clippings. If your lawn is over 20 years old, you may be able to reduce the fertilizer applied even more.

Years of research conducted by both Dr. Stahnke and Dr. Eric Miltner at WSU's Puyallup research station continues to validate that using fertilizer with at least 50 percent of it in a slow-release form gives the best return when it comes to turfgrass vigor. Stahnke is quick to add that the most accurate way to determine if your turf may be lacking in nutrients is to take a soil test. Nutrients like calcium, phosphorus and potassium are frequently deficient in soils west of the Cascades. The soil pH for turfgrasses should be slightly acidic (somewhere between 5.5 and 6.0), in order to limit disease development during our wet months. Sulfur within the fertilizers applied can help keep the pH in this range.

Just like anything else, too much of any one thing is not good and a balanced fertilizer is needed. Homeowners should use a complete fertilizer with a 3-1-2 ratio (N-P-K) on established lawns, to supplement any lacking phosphorus and potassium. Often sold as a 15-5-10 or a 12-4-8, the fertilizer should be applied at a rate which is equal to approximately one pound of nitrogen per 1,000 square feet of turf. (If you are using 15-5-10 for example, you would need to apply approximately 6.5 pounds of the actual fertilizer product per 1,000 square feet in order to get one pound of actual nitrogen.)

Organic turf fertilizers release nutrients slowly, and are most effective when used during the warm season (Memorial Day and Labor Day applications). Most organic fertilizers contain more Phosphorous than needed by turf, and continued application could lead to excess Phosphorous in the soil.

No matter what type of product you apply, make sure that if any granules of product end up on an impervious surface such as a driveway, sidewalk or street, that you sweep it back into the grass or landscape so that the granule is not directly washed into the surface water if it rains or the lawn is irrigated.

Question: We planted several fruit trees last year and are wondering if we should fertilize them? Is there a specific kind of fertilizer we should use?

Answer: For practical purposes, it would be best to use a complete fertilizer, like 10-10-10. However, nitrogen is the number one fertilizer needed by fruit trees. Bearing fruit trees as a general rule should have an annual application of nitrogen. Fruit trees have the highest demand for nitrogen early in the season around bloom time. Therefore, be sure to fertilize your trees in late March or early April.

For trees 1 to 2 years old, apply 1/4 to 1/2 pound of 10-10-10 per tree; on trees 3 to 4 years old, apply 1/2-2 lbs. of 10-10-10 per tree; on trees 5 to 10 years old, apply 2 to 4 lbs. of 10-10-10 per tree and trees over 10 years old should receive 4 to 6 pounds of 10-10-10. Spread the fertilizer evenly on the ground away from the trunk of the tree and to the outer spread of the branches. It is not necessary to drill fertilizer into the ground.

On bearing apple trees, eight to 10 inches of terminal growth at the tips of branches is preferred. Less growth results in smaller apples, less production, but good fruit color.

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