...fall is a great time to reseed bare and thinning areas...
The autumn months are perfect for doing work on your lawn. Work done in these months will prepare your lawn for overwintering and the following spring and summer months. The goal is to improve the overall health and appearance of your lawn while saving money, time and water and reducing chemical use. Whether you are someone who is meticulous about your lawn or someone who prefers a care-free lawn, in both cases the grass may be stressed and in poor health. These steps will help your lawn look better and be healthier.
- Identify areas were the grass is clearly doing poorly, and replace with a garden of native shrubs and perennials. Grass will always do poorly and require high maintenance and inputs under the shade of mature trees and in poorly draining soils. The removal and replacement of the grass can be done in stages. Learn about the wonderful plants that can bring birds and other wildlife to your yard by taking the free Naturescaping Workshop offered by Stream Team and WSU Native Plant Salvage Project on November 8. Or, if you want to get started sooner, get low cost, beautiful native and nonnative drought tolerant plants and expert advice at the Native Plant Salvage plant sale on September 30 (see page 15 for more details).
- Determine the pH, fertility and compaction of your soil. Grass needs nutrients that are taken up by the roots from the soil. Applying chemical fertilizers and pesticides will not fix the soil. Just like in a vegetable garden, the lawn’s soil needs to be improved to support the plants. Get a soil test done from Thurston Conservation District (360-754-3588) or Black Lake Organics (360-786-0537) where, for a small fee, you will receive a comprehensive analysis that includes soil texture and recommendations for soil improvement. You can also purchase an inexpensive soil test kit from a garden store.
Soils in Western Washington are naturally acidic (under 7 on the pH scale). Turf grasses prefer a pH between 5.5 and 7. If the pH of your soil is above 5.5, there is no need to add lime. According to WSU fact sheet The Role of Lime in Turf Management, "Lime is not a cure-all for many common problems of lawns. The most important role of lime is to maintain pH between 5.5 and 7.0, which is the most favorable range for bacterial breakdown of organic residues and the availability of other plant nutrients. Lime will not control lawn moss and most other weeds in the Pacific Northwest."
Fertilizing the lawn is complicated. This is why fertilizer companies have developed general use "recipe" type products. Using these products bypasses knowing your soil needs as well as improving the soil. It's best to learn your soil’s fertilizing needs with a soil test, improve your soil with aeration and the addition of fine compost and over-seeding, and, if needed, apply a slow-release type fertilizer according to the recommendations from the soil test.
How to understand a fertilizer label
The three numbers on the fertilizer label represent the N-P-K ratio. The numbers are always in the same order and represent the percentage of nitrogen, phosphorus and potassium in the fertilizer.
- N-Nitrogen promotes strong leaf growth
- P-Phosphorous encourages roots, flowers, seeds and fruit
- K-Potassium is critical for overall plant health
Fertilizers with larger numbers (such as 29-2-3 or 18-16-10) are typically "quick release", with all the nitrogen released immediately. These fertilizers are made with ammonium sulfate, urea and ammonium nitrate. Very small amounts of this type of fertilizer is needed, and it’s tricky to spread a little amount of fertilizer over a large area. Over-fertilizing with quick-release fertilizers is common. Because quick-release fertilizer is highly soluble, over-fertilizing can burn the grass, cause plant stress and pest and disease problems. It can also create polluted runoff that can harm our rivers, streams, lakes and groundwater.
Slow-release fertilizers are an excellent alternative to avoid these pitfalls. Slowrelease fertilizers can be natural or organic fertilizers, or "coated" chemical fertilizers that are gradually released. Look for at least 50% insoluble nitrogen on the label.
(You may have to ask a staff person at the store to assist you to find it, since the majority of fertilizers contain a highly soluble nitrogen source.)
Avoid purchasing fertilizers with insect, disease or weed "control". These products allow broad application of herbicides and/or pesticides all over your yard. Spot treatment, whether by hand pulling or an appropriate herbicide, is more effective, cheaper and less polluting. In addition, some weed products contain herbicides or pesticides that target species that are not even present in the Pacific Northwest. These are a waste of money as well as potentially harmful.
Fertilizer recommendation from Washington State University:
1 x per year. . . . . . . . . . . . . . . . . . Sept.
2 x per year . . . . . . . . . . . Sept. & June
4 x per year. . . . Sept., June, April, Nov.
For potassium, the fall fertilization will encourage deep root growth, so equal ratios of N and K are recommended, such as 6:1:6. A 3:1:2 ratio has been recommended for spring fertilizing. Apply no more than 1 pound of nitrogen per 1,000 square feet per application. Check the weather, and apply before a light rain.
Always use a properly calibrated fertilizer spreader and avoid getting fertilizer on sidewalks, driveways and the road. Sweep up and throw away any fertilizer that spills onto pavement.
Check for soil compaction
Can you easily push a screw driver into the ground without pounding? If not, your soil is compacted and this keeps air, water and nutrients from entering the soil. Compacted soils have less microbial activity. Grass grown in compacted soils has shallower roots, more thatch and is generally weaker. If your soil is compacted, use a hand corer or mechanical aerator to punch holes through the grass and into the soil. Thurston County and the cities of Olympia and Tumwater will subsidize a one-day rental of an aerator when at least three neighbors agree to aerate their lawns together. (Conditions apply. For more information, contact a Stream Team coordinator)
Overseed for a thicker healthier lawn
Fall is a great time to reseed bare and thinning areas of your lawn. Select a grass blend that is suited for your soil and light conditions. In Western Washington, the recommended types of turf grasses are perennial ryegrass, fine-leafed fescues, bentgrasses and turf-type tall fescues. Kentucky bluegrass is not recommended for Western Washington. Each grass type has its own characteristics for sunlight needs, durability and other conditions (see chart).
Aerate your lawn, spread a ¼ inch of loam soil or fine compost over the grass, then sow grass seeds. Water and fertilize with slow-release fertilizer. Water frequently to keep the soil moist until grass is established.
Know how to recognize and measure thatch
Thatch is a brown, straw-colored layer of living and dead stems, leaves and roots which accumulates between the green grass and the soil. A small thatch layer (less than ½ inch) is helpful, as it functions like mulch in a flower bed to conserve water and block weeds. Too much thatch, over ½ inch, is a sign of unhealthy grass. Excessive thatch blocks water, nutrients and air from reaching the roots. Once thatch is over ½ inch, it needs to be removed using a dethatching machine. Early fall or spring are good times to dethatch and reseed with half the seeding rate amount recommended for a new lawn. Following the dethatching, lawn care practices should be changed to avoid thatch build up in the future.
Watering deeply once per week, fertilizing lightly and infrequently, aerating annually, avoiding chemicals and using a higher mow deck setting are all practices to follow to keep thatch at a healthy level.
Choose Your Turf
|Shade tolerance||Drought tolerance||Mowing ht (in inches)||Characterisitcs|
|Perennial rye||Low||Low||1.5||High wear tolerance; little thatch; blends well w/other grasses|
|Tall fescue||High||High||2||Deep roots; can grow in moderately wet soils; drought tolerant only if grass roots are deep|
|Fine fescue||Highest||Highest||1.5||Tolerates light wear, but slow to recover from excessive wear; low maintenance grass; develops thatch more easily|
|Colonial bentgrass||Medium||Mediumlow||.75||Produces a lot of thatch; mowed short; high maintenance|