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Some management practices will cause turf problems to develop that require renovation to correct. These problems and a brief description are discussed.
GRASS SELECTION
Turf-type perennial ryegrasses, fine-leaved fescues, and bentgrasses are well-adapted to western Washington, with more evaluation of tall fescues being conducted. Kentucky bluegrasses are usually shortlived in western Washington and only selected improved cultivars should be used and never seeded alone.
Gardeners who prefer bentgrass lawns in western Washington should plant only the colonial types such as Bardot, Tracenta, Highland, Astoria, or Exeter. Never plant creeping bentgrasses such as Seaside, Penncross, Pennlinks, Putter, or Emerald. These varieties have vigorous growth habits and excessive thatch forming characteristics for home lawns. The average gardener does not have the equipment and, frequently, the knowledge necessary to maintain the varieties over a large number of years.
MOWING PRACTICES
Mowing height can influence the lengthof life of lawns and also affect the appearance. The following heights are recommended for grasses in western Washington.
| Kentucky bluegrass | 1 - 1 1/2 inches |
| Fine-leaved fescues | 1 - 1 1/2 inches |
| Turftype perennial ryegrass | 1 - 1 1/2 inches |
| Bentgrass | 1/2 - 3/4 inches |
| Turftype tall fescues | 1 1/2 - 2 inches |
If bentgrass is planted as a mixture in western Washington lawns, the lawn should be mowed at 1/2 to 3/4 inches high. This may hasten the loss of Kentucky bluegrass and fine fescues, but will prevent serious problems of excessive thatch formation. This mowing height will not significantly decrease the turftype perennial ryegrasses. If these mowing heights are maintained, renovation should never become necessary provided the lawn is properly maintained through fertilization, watering, mowing, and annual dethatching.
THATCH REMOVAL
Power rake good quality lawns if thatch exceeds 1/2inch in depth. The removal of dead stems and surface roots and accumulated organic debris of all sorts will prevent excessive thatch formation and the necessity for renovation. As thatch builds up in a lawn, the mower tends to run higher from the ground, especially where lightweight mowers are used. Excess thatch can also serve as a home for insects and increased disease development.
WATERING PRACTICES
Saturated soils tend to induce surface rooting. Roots will develop where oxygen supplies are greatest and saturated soils have very low oxygen concentrations.Thorough, infrequent watering is much more desirable than light, frequent applications and is regulated by soil texture and depth. Light, frequent applications tend to encourage weedy grasses and certain broadleaf weeds and decrease the quality of desirable grasses. Close observation of the turf will indicate the need for water before wilting or browning occurs. A soil probe can be used to feel the soil for its moisture content.
TURFGRASS LOSSES FROM PESTS
Lawns severely damaged by insects, diseases, or uncontrolled weeds may have to be renovated to correct the problem. Discreet and proper use of pesticides as necessary can control these problems, giving longer life and beauty to the lawn as well as being environmentally conscious.
RENOVATION PROCEDURE
Favorable spring and fall growing weather will hasten lawn recovery following renovation. Summer renovation may result in slow recovery and is generally not recommended. Total kill, sod removal, and reestablishment can be accomplished during the late summer period.
Adjust the mower to approximately 3/4 inch and mow the lawn thoroughly-slightly lower for bentgrasses.
Power rake the lawn as many times as may be necessary to remove accumulated thatch. It is best to dethatch in opposite directions. Thoroughness is important.
When all thatch has been removed, mow the turf again at approximately 3/4 inch high.
Grass stems and crowns may be excessively thinned by heavy raking. If this is the case, overseed the lawn at a rate of 1/2 the recommended rate of seed per 1,000 square feet for establishment, using varieties recommended for your area.
Before overseeding, remove sod from all high and low spots, adjust these areas to the proper lawn grade and replace the sod to obtain a uniformly smooth surface.
Growth will initiate quickly from grass stems and crowns that were not removed through the raking process and from the additional seed planted. Although the turf may be somewhat thin, mowing must be practiced regularly at the recommended mowing height. It is important to maintain surface moisture for germination of the newly applied seed.
Lawns having large patches of coarse, weedy grasses such as velvetgrass, unimproved tall-fescue, orchardgrass, or nonturf type perennial ryegrasses can be best renovated if all vegetation is killed with glyphosate (Roundup@). Apply chemicals in mid-spring or late summer. It will probably take more than one application to kill creeping perennial grasses which have rhizomes. You have a choice of removing the dead sod or following steps 1-6 above for reestablishing new turf. It is advisable to increase the seeding rates recommended for new lawns in this case. One pound of available nitrogen per 1,000 square feet from complete starter fertilizers applied following seeding will hasten establishment. If the soil is extremely sandy, two 1/2 lb. nitrogen applications per 1,000 square feet should be made instead of the single 1 lb. application to avoid the possibility of nutrient loss.
A good lawn should essentially last a lifetime if properly fertilized, watered, mowed, dethatched and overseeded as needed. Pests should be controlled when diagnosed as being at harmful levels to the turf area.
For further information contact your local WSU Extension Office.
Use pesticides with care. Apply them only to plant, animals, or sites listed on the label. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disrgard label directions. If pesticides are spilled on skin or clothing, remove clothing and wash skin thoroughly. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.
