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Lawn Improvement Programs Zac Reicher and Clark Throssell Purdue University Turfgrass Specialists

AY-13

Whether your lawn is thin from the rigors of summer or from neglect, fall is the best time of the year to improve your lawn. Some lawns can be drastically improved with proper fertilization and weed control in fall whereas others need reseeding in some areas or even complete renovation. If you are faced with improving your lawn in spring, refer to AY-20, Seeding a Turf Area in the Spring.

Lawn ImprovementThrough Fertilization and Weed Control
Most of us may be fairly happy with our lawns and may not willing nor needing to reseed, but we can still dramatically improve our lawn with fertilizing and possibly some weed control.

September is the most important time to fertilize a cool season turfgrass to encourage rooting and increased density. Fertilization should be done in mid-September with a product that has a nutrient ratio of nitrogen, phosphorus and potassium of about 4-1-2. Examples of fertilizers with this ratio would be 24-6-12 or 20-5-10. Apply fertilizer at 1.0 lb N/1000 ft².

A second fertilizer application should be made after the last mowing of the year but while the turfgrass is still green. A soluble nitrogen source, such as urea, is very effective for late fall fertilization. The nitrogen should be applied at the rate of 1.5 lbs /1000 ft². Nitrogen is the most important nutrient to apply for a late fall fertilization.

Two applications of fertilizer should be adequate to maintain or even improve most lawns in the fall. A third application in mid-October could boost your lawn even more if it was especially thin after summer. Apply 1.0 lb /1000 ft² in with a soluble nitrogen source like urea. Be sure to reduce the rate of application of the November application to 1.0 lb /1000 ft². The October application may encourage a winter disease called snow mold, so this application should be used only on very thin lawns where the increase in density is worth the risk of increased snow mold. For more information, refer to AY-22, Fertilizing Established Lawns.

An application of a broadleaf herbicide containing 2,4-D, MCPP and dicamba in mid-October will control dandelions, plantain, wild violets, clover, and black medic among other weeds. Read and follow all directions on the herbicide label when using the product. Be careful when using these products because they may damage desired vegetation such as flowers, trees, shrubs, or vegetables. Apply this product on a sunny day when no rain is forecast and temperatures are above 50^oF. For more information, refer to AY-9, Control of Broadleaf Weeds in Homelawns.

Improving Your Lawn Through Overseeding
The density of many lawns can be improved by introducing seed into the lawn and allowing these plants to germinate. The optimum time to seed cool-season turfgrasses is between Aug. 15 and Sept. 1 in central IN, a week earlier in northern IN, and a week or so later in southern IN.

• Mow the area to 1 or 1.5 inches to reduce competition from established grasses.

• Apply a starter fertilizer (high in phosphorus) over the entire lawn at 1.5 lbs P₂O₅/1000 ft².

• Aerify the area, punching at least 20 to 40 holes/ft² with the largest tines possible. This will increase the seed-soil contact and improve germination and establishment rate. You can never over-aerify at this time, so make many passes over the lawn. A power raking at this time will also help to increase the seed-soil contact.

• Apply the seed to the lawn with either a dropseeder or a power overseeder which is a machine that will drop the seeds into small grooves that it cuts into the soil. Try to make 2 to 4 passes over the lawn in different directions with either the dropseeder or the power overseeder to insure a uniform seeding. Table 1 lists the suggested seeding rates.

• Water the newly-seeded area three to four times daily. Light, frequent irrigation is the rule.

• Mow frequently to limit the competition from the established turf. Mow at 1.5 inches until new seedlings have been cut at least two times. After that, raise the mowing height in 1/2 inch intervals over the next three weeks until a normal mowing height of 2.5 to 3.5 inches is reached.

• Six weeks after germination, apply 1.0 lb N/1000 ft² with a fertilizer containing N, P, and K.

• Follow the previously mentioned instructions for improving your lawn through fertilization and weed control.

Improving Your Lawn Through Complete Renovation
Some lawns may be in need of complete renovation and reseeding because the lawn contains old or poor performing species or cultivars; is damaged from traffic, diseases,or other stresses; is on severly compacted soil; contains more than 1/2 inch of thatch; and/or contains many grassy perennial weeds like nimblewill or quackgrass.

• Apply a nonselective herbicide like glyphosate (Roundup or Kleenup) to kill the undesirable grasses. Multiple applications may be needed to control tough-to-control grasses like quckgrass or zoysia. Refer to AY-11, Controlling Perennial Weedy Grasses in Turf. Allow the herbicide to work four at least 3 days before taking the next step.

• Depending on your lawn, you can use one of three methods to prepare the soil:

1. On uncompacted soils with no thatch, an aerifier can be used to expose the soils like previously mentioned. A power rake set to cut 1/8 to 1/4 inch into the soil works also will work well. Follow this with a power overseeder or drop seeding.

2. On compacted soils, till the soil to 4 inches or more, rake smooth, allow it to settle for a week or two with irrigation or a heavy rain fall, rake to the final finish, and then drop seed.

3. On lawns with significant thatch, a power rake should be used to loosen and remove as much of the thatch as possible. If the thatch is over 1 inch thick, either use a sod cutter to remove the thatch or till the soil turning under the thatch. Follow this with drop seeding or power overseeding.

• Just before seeding, apply a starter fertilizer (high in phosphorus) over the entire lawn at 1.5 lbs P₂O₅/1000 ft².

• After seeding, roll the lawn with a light roller to insure seed-soil contact.

• Water the newly-seeded area three to four times daily. Light, frequent irrigation is the rule.

• Mow as soon as the first few blades reach about 2 inches and mow Kentucky bluegrass, perennial rye, and fine fescue at 1.5 inches and tall fescue at 2.0 inches. After the first three to four mowings, you can adjust your mower to the permanent mowing height which is 2.5 - 3.5 inches for Kentucky bluegrass, perennial rye, and fine fescue and 3.0 - 4.0 inches for tall fescue.

• Six weeks after germination, apply 1.0 lb N/1000 ft² with a fertilizer containing N, P, and K.

• Follow the previously-mentioned instructions for improving your lawn through fertilization and weed control. For more information, refer to AY-3, Establishing Lawns from Seed.

Purdue University

Indiana 47907

3/98

Cooperative Extension work in Agriculture and Home Economics, state of Indiana, Purdue University, and U.S. Department of Agriculture cooperating;
H. A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914.
The Purdue University Cooperative Extension Service is an equal opportunity/equal access institution

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