University of Missouri Extension

G6705, Revised May 2014

Cool-Season Grasses: Lawn Maintenance Calendar

Brad S. Fresenburg
Turfgrass State Specialist
Division of Plant Sciences
Lee Miller
Extension Turfgrass Pathologist
Division of Plant Sciences

Established lawns may be maintained at different levels of perfection according to individual situations and desires, but good lawns seldom “just happen.” This summary outlines major steps required to maintain a high-quality lawn year round.

Steps in boldface type indicate a minimum program where time, money or interest dictates a usable lawn with least effort. Other selected steps of the schedule may be adopted occasionally or in alternate years to upgrade the program.

Timing is approximate for central Missouri. It may vary two weeks or more from one area to another in the state or from year to year.

Note
This publication refers primarily to cool-season grasses such as Kentucky bluegrass, perennial ryegrass, tall fescue and fine fescue. For zoysia and Bermuda grass lawns, see MU Extension publication G6706, Establishment and Care of Zoysiagrass Lawns.

March

April

May

June

July

August

September

October and November

Maintenance

The key to good maintenance is doing those things that best counterbalance unfavorable conditions in the lawn environment. To attain equal success, lawns on soils of inferior physical quality or low fertility require more attention than those on deep, friable loam-type soils. Followed properly, the steps below should provide satisfactory lawns.

Fertilization

Variation in soils, lawn standards and grasses require different approaches to lawn fertilization. The ideal program provides for uniform moderate growth throughout the season. Such growth can be provided through fertilization programs that use organic forms of nitrogen.

Problems arise when rates and forms of fertilizer cause irregular “spurts of growth,” especially in spring and summer. Turf that is not fertilized enough has little competitive ability against weeds or disease.

Nitrogen recommendations and materials tend to overemphasize the dark green color and fast growth response. In too many cases, this has been detrimental to balanced plant growth and health. For example, much emphasis has been given to early spring as the best time to fertilize bluegrass. If a lawn is stunted and has a pale to yellowish-green appearance, a very moderate feeding at this time would be advisable.

On the other hand, fertilizing a lawn that already had moderate vigor at the time most of us get “spring gardening fever” will stimulate excessive succulent growth. The grass becomes more susceptible to fungi, which will take their toll a few weeks later during summer stress. In addition, excessive leaf growth usually occurs at the expense of new root growth, placing the plant at a further disadvantage for summer.

When to fertilize

All lawns should be fertilized at least once a year. Additional fertilization will depend on the desired level of turf appearance, turfgrass species, soil type and fertilizer carrier. As indicated in Table 1, other fertilizer applications may be desirable and even necessary.

If only one fertilization per year is desired, September is an excellent time for it.

When a second application is desired, mid-October is a good time for it. Moderate rates in October or November, after days are cool enough to discourage vigorous leaf growth (50 degrees F), will help prolong green color into the winter and at the same time encourage development of a stronger root system for next spring’s growth.

If a spring fertilization is desired, it should be done in mid-April to early May. Two or three fertilizer applications in the fall may eliminate the need for a spring application.

When fertilizer is applied at higher rates, give greater attention to thatch- and disease-control measures, as well as to watering.

Table 1
Fertilizer application schedule

Turf type Nitrogen, apply at recommended rates* May September October November
Common type Kentucky bluegrasses 2 to 3 pounds per year X X X  
Higher quality bluegrasses 4 to 5 pounds per year X X X X
Red fescues 2 pounds per year X X X  
Bluegrass and red fescue 2 to 3 pounds per year X X X  
Tall fescue or ryegrass 3 to 4 pounds per year X X X  
* Rates usually supply about 1 pound of nitrogen per 1,000 square feet. (In May, rates can be reduced to 1/2 to 3/4 pound of nitrogen per 1,000 square feet.)

Nitrogen fertilizer

The two basic types of nitrogen fertilizer are soluble and slow release. Soluble types are available quickly to plants even at low temperatures, stimulate rapid growth and are depleted quickly (3 to 4 weeks). Steady, uniform plant growth requires frequent, light applications. Slow-release types of several different forms release nutrients to plants over longer periods of time (6 to 8 weeks) and very slowly at low temperatures.

Lawn specialty fertilizers often contain 24 to 50 percent of the total nitrogen in slow-release form and the remainder in quickly soluble forms. This combination gives immediate response in cold weather while the remainder is available over a longer period.

When 35 to 50 percent or more of the nitrogen is a slow-release type, rates may be increased at least 50 percent, especially for high-quality management. With these fertilizers, frequency of application may sometimes be reduced.

Precaution
Nitrogen sources from urea (quickly soluble) should not be confused with urea-formaldehyde (UF; slowly available).

Rates and frequency

Recommendations are usually based on amounts required to supply a given amount of nitrogen per 1,000 square feet of lawn. Most lawn fertilizers are “complete” in that they contain nitrogen (N), phosphorus (P) and potassium (K), and so, the amount of phosphorus and potassium applied is determined by the ratio of these two elements to nitrogen.

Two fertilizers with label analyses of 20-5-10 and 12-12-12 would contain 20 and 12 percent N, 5 and 12 percent P, and 10 and 12 percent K, respectively. The N:P:K ratio would be 4:1:2 for the first fertilizer and 1:1:1 for the second.

The amount of fertilizer required to apply 1 pound of nitrogen to 1,000 square feet can be calculated by dividing 100 by the percent of nitrogen in the fertilizer (for example, 100 ÷ 20 = 5 pounds fertilizer per 1,000 square feet). The same formula would apply for phosphorus, potassium or any other nutrient percent.

Suggested annual fertilization schedule
For routine maintenance where a soil test or experience indicates no major deficiencies, use a lawn fertilizer with an approximate ratio of 3:1:1 or 4:1:1 or 4:1:2 at recommended rates according to the schedule in Table 1.

Where a soil test indicates low phosphorus or potassium levels, or where basic fertility levels are not known, use fertilizers with a ratio that more closely approximates 1:1:1 or 2:1:1 or 3:1:2. If lawn application rates are not given on the container, amounts to apply can be calculated as in the example above.

Lime
Do not routinely apply lime to established lawns unless a soil test indicates a need. Excess can be as harmful as deficiency. Established lawn soils seldom need to be limed unless a soil test indicates a moderately to severely acid soil of pH 5.8 or lower.

Where such need is indicated, apply finely ground or specially pelletized agricultural limestone at rates up to 50 pounds per 1,000 square feet. If more is required, make separate applications about six months apart. Limestone can be applied almost any time, but fall or early winter is the best time.

Mowing

Mowing height and frequency directly affect the performance of a lawn. The shorter turf is cut, the more frequently it should be mowed. The common practice of mowing a lawn short under the assumption it will require less frequent cutting is responsible for much lawn deterioration.

When grass is cut too closely, not enough leaf surface remains to manufacture necessary foods for sustenance and root growth. For this reason, a standard guide is to never remove more than one-third of the green leaf area with a single mowing. If a mowing is missed, cut only half the way back to the intended height, and then a couple of days later cut to the regular level. Recommended mowing heights are presented in Table 2.

Clippings need not always be removed. When they are short enough to filter down to the soil surface, they decay and recycle nutrients back to the soil. Remove clippings when they remain on the surface or when excessive thatch is already causing a problem.

Table 2
Recommended seasonal mowing heights* for cool-season grasses in Missouri

Turfgrass Spring Summer** Fall
Tall fescue 2 to 3.5 inches 3 to 4 inches 2.5 to 3.5 inches
Kentucky bluegrass 1.5 to 2.5 inches 2 to 3.5 inches 1.5 to 2.5 inches
Perennial ryegrass 1.5 to 2.5 inches 2.5 to 3.5 inches 1.5 to 2 inches
Creeping red fescue 1 to 2 inches 2 to 3 inches 1 to 2 inches
Chewings fescue 1 to 2 inches 2 to 3 inches 1 to 2 inches
Hard fescue 1.5 to 2.5 inches 2 to 3 inches 1.5 to 2.5inches
Sheep fescue 1.5 to 2.5 inches 2 to 3 inches 1.5 to 2.5 inches
*Mowing heights may be adjusted according to climatic conditions, intensity of culture and intended use.
**Summer mowing heights should be used when turfgrasses are grown in shaded conditions.

Watering

Bluegrasses, fescues and other cool-season grasses naturally protect themselves by going into a semidormant stage during periods of high temperature or drought. They cease growth and turn brown but bounce back quickly with sufficient water and cooler temperatures, usually in September.

Except in cases of extreme prolonged drought, tall fescue and Kentucky bluegrass do not need water to stay alive during the summer; however, their appearance suffers. During dormancy, drought-tolerant weeds such as crabgrass, plantain, thistles and dandelion dominate lawns.

Because of its deep extensive root system, tall fescue remains green longer into the summer than other nonirrigated cool-season grasses.

Kentucky bluegrass has many underground stems, called rhizomes. Each rhizome can produce several new bluegrass shoots that result in turf thickening when water becomes available following summer dormancy, usually in September.

Perennial ryegrass and fescue, other than tall fescue, should not be grown as monocultures — only one grass species — without irrigation in Missouri because of their tendency to bunch during severe moisture stress.

The principal purpose of summer watering is to maintain an attractive green surface when it may be appreciated the most. Watering will not substitute for poor fertility or improper mowing, and can encourage crabgrass and other weed problems. Extra growth stimulated by watering increases fertility requirements, thatch accumulation and other problems.

If, in the desire for a summer green lawn, you cannot give attention to related management, let the turf follow its natural tendencies to go dormant during summer. (Plants are brown in appearance from lack of water but are not necessarily dead.) Homeowners who have a lawn-care service should not allow their lawn to enter drought dormancy.

Rules for watering

Aeration

On clay- or silt-type soils, or any turf receiving constant traffic, soil sealing and compacting can seriously impair turf growth. Grass roots are injured because air, water and fertilizers cannot reach them in sufficient quantities. Mechanical aeration to break through this barrier is essential for continued turf health. Fertilizer applications following aeration most efficiently provide nutrients to the turf roots.

Aeration is best done by power equipment that pulls out small cores of soil, or by cutting vertical grooves to provide openings every 3 to 4 inches. Power equipment is usually available at rental stores. Lawn-care companies may also provide this service to their customers.

For small areas, suitable hand-equipment is available, but using it is hard work. Even an ordinary spading fork plunged into the soil at 3-inch intervals when the soil is lightly moist — not wet — is far better than nothing at all.

Aeration should be done at least once a year where compaction is a problem. Early fall is the best time for bluegrass lawns, but aeration will be highly beneficial anytime the grass is actively growing, except possibly during midsummer heat.

Thatch control

Thatch is a layer of undecayed plant parts accumulating at the turf base. It forms a barrier to water and air movement in the same manner as compaction.

Thatch is primarily a problem of intensely fertilized and watered lawns. Even though clippings are removed regularly, thatch still can form because old plants and basal leaves are more resistant to decay than are the clippings.

Thatch removal should be initiated whenever accumulation exceeds 1/2 inch. Early fall is the preferred time for dethatching lawns.

For more information on thatch, see MU Extension publication G6708, Thatch — Enemy of Lawns.

Top-dressing

Top-dressing is the periodic addition of a thin layer, about 1/4 to 1/2 inch, of soil to the surface of growing turf. Mixing soil with accumulating debris hastens thatch decay. Shallow depressions in a turf can be leveled gradually by this practice as well.

The texture of the top-dressing material should be similar to or coarser than the soil on which the turf already exists. When top-dressing with soil to reduce thatch, the addition of compost or peat moss is not required because the thatch layer is already high in organic matter.

Top-dressing may be done immediately after coring, dethatching or slicing. Never bury the existing turf with too much top-dressing soil. After top-dressing, at least three-fourths of the grass plant should be exposed to sunlight. Never top-dress during the heat of the summer.

Rolling

Rolling is not desirable for smooth, uneven lawns. Surface compaction is common in many lawns, without adding to the problem by heavy rolling. Rolling moist soil causes maximum compaction — a fine way to build roadways but not soils for turf.

When late winter freezing and thawing have resulted in “heaving” young plants out of the ground, or if mole activity is serious, rolling may be required and is acceptable. In such cases, roll soon after spring thaw when the soil surface is relatively dry, and use as light a roller as possible. Don’t roll more than is absolutely necessary.

Weed control

The best weed control is a healthy, dense, competitive turf. Correct cultural practices to achieve this will keep out most weeds. In particular, maintaining a proper mowing height and not cutting lawns too short will reduce weed invasion.

Chemical weed killers are useful but should not be relied upon entirely to cure lawn weed problems. Suggestions for timing herbicide applications for several common weed problems are indicated in the calendar of this guide.

Relative merits of using fertilizer-herbicide (weed and feed) or fertilizer-insecticide combinations should be considered carefully before they are used indiscriminately. In many cases, at least one of the ingredients may not be needed or will be used at an inopportune time. (See MU Extension publication IPM1009, Turfgrass and Weeds.)

Renovation

If your lawn is less than acceptable but contains at least 40 percent desirable grasses, you may be able to replant without preparing a completely new seedbed. Start in August with steps similar to the following:

If the original problem was due to soil itself, poor drainage or excessively thick thatch, till the lawn and start over following the steps for establishing a new lawn. (See MU Extension publication G6700, Cool-Season Grasses: Lawn Establishment and Renovation.)

Disease and insect problems

Prevention is the best approach to disease problems in home lawns. Often by the time the disease is diagnosed, the damage has been done.

Controlling thatch, avoiding frequent sprinklings and fertilizing properly for healthy but not succulent grasses are simple lawn-grooming practices that aid disease prevention.

Two major insect pests are white grubs and sod webworm. White grubs are described in MU Extension publication IPM1020, Turfgrass and Insects. Routinely inspect the lawn for white grubs and sod webworms. Treat only after the insects have been properly identified and only when they are in sufficient numbers to cause a noticeable loss of turf. Treating lawns every year with insecticides as prevention is neither necessary nor advised.

G6705, revised May 2014

G6705 Cool-Season Grasses: Lawn Maintenance Calendar | University of Missouri Extension

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