Late Summer Lawn Care

As summer gets ready to move into fall there are some important lawn care tasks to continue and new ones to be done.  We should continue to mow at the proper height depending on grass type. Mow centipede to 1 to 2 inches. Most people mow to 2 inches since home lawns are often too uneven to mow lower without scalping the grass. Since the rule of thumb in mowing grass is to only remove one third of the grass blades, mow when the grass gets 1.5 inches (for 1 inch mowing) to 3 inches tall (for 2 inch mowing). Make sure to raise the mowing height to 2 inches several weeks before expected frost to prevent winter injury. The best mowing height for bermuda is 1 to 2 inches. Mow the grass before it gets 1.5 to 3 inches tall. You should always grasscycle by leaving the grass clippings on the lawn. This technique will provide up to 25% of the lawn’s fertilizer needs. Mow St. Augustine to 3 to 4 inches, zoysia to 1 to 2 inches depending on variety and tall fescue to 3 to 4 inches.

Fertilization is important to have a healthy lawn but be careful not to overdo it. Between now and 4 to 6 weeks before expected killing frost  (mid-September) fertilize warm season grasses with 1 pound of potassium per 1,000 square feet. One pound of potassium can be applied by using 1.5 pounds of muriate of potash (0-0-60), 2 pounds of potassium sulfate (0-0-50), or 4.5 pounds of sul-po-mag (0-0-22) per 1,000 square feet. This potassium application will help prevent damage to warm season grasses from the stresses of winter and get them off to a good start next spring.  This is the way to winterize your warm season lawn. Do not fertilize any warm season lawn with a high rate of nitrogen containing fertilizer after August.

Fertilizing at the wrong time and with excess nitrogen is one of the reasons we have so many problems with centipede.  If you have already fertilized centipede with a fertilizer containing nitrogen there is no need to do it again. DO NOT APPLY NITROGEN CONTAINING FERTILIZERS TO CENTIPEDE AFTER AUGUST.  Bermuda can be fertilized in August at the rate of 8 pounds of 12-4-8 or 6 pounds of 16-4-8 per 1000 square feet. Use half that amount on St. Augustine or zoysia in August. To give bermuda one final push for good fall growth it can be fertilized at half the August rate in September. Bermudagrass is the only warm season lawn I would recommend any nitrogen on in September.

Watering hasn’t been needed much this year. About 1 inch of water should be applied when irrigating. The best irrigation timing is the early morning when the grass begins to turn a bluish gray color indicating drought stress. This method conserves the most water.

Insects are a concern in lawns but rarely a problem.  The lawn insects most worry about are white grubs.  White grubs are the larvae of beetles like the Japanese beetle, green June bug, and chafer beetle.  You might have seen a few green June bugs flying over the lawn during the past few weeks getting ready to lay eggs. Don’t worry about them since their grubs only feed on decaying organic matter, not living roots. White grubs of other types rarely cause brown patches to appear in turf as they feed on and damage grass roots.  How do you determine whether or not to take control measures?  Cut a 1-foot square section of sod on 3 sides and roll it back.  Do this in several locations.  An average of 15 or more grubs curled in a c-shape per square foot justifies control. These populations are rarely seen in our area so pesticide applications are usually not needed. The big grubs that wriggle on their backs are the green June beetle grubs and are not of concern.

Weeds are always a hot topic.  No matter what weeds you have, now is not the best time for control.  Summer annual weeds (like common lespedeza or crabgrass) are more easily controlled from April to June.  Perennial weeds are easier to control from October to November and April to May.  Winter annual weeds can be controlled from November to March. For prevention of annual bluegrass and winter broadleaf weeds, a September application of pre-emergence herbicides containing benefin, trifluralin, dithiopyr, or pendimethalin can be used. Do not apply a pre-emergence herbicide if you plan on over-seeding in the fall. These products are often sold as crabgrass preventers but are labeled for late summer and fall application for prevention of winter weeds.

If you have questions about lawn or garden care give the Pitt County Extension Master Gardener Volunteers a call at 902-1705 or email pittcomgv@hotmail.com. You can find more gardening information at http://pitt.ces.ncsu.edu.

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