'Do it now': Extreme weather leads homeowners to worry about condition of lawns

Several homeowners recently have expressed the need to reseed their cool season lawn (bluegrass, fescue and rye). The extreme weather conditions have done a number on it, and they want to get it back into shape this fall.

The most often asked question is, "Should I seed now, later this fall, or wait until next spring?" The answer to this question is, "Do it now." If you wait until next spring, the soils will be cool and seed will take a long time to germinate.

Then about the time the lawn seed germinates, so will crab grass and other lawn weed seed. If you put down a pre-emergent herbicide for crab grass, it will inhibit lawn seed to germinate. If you wait until all of the lawn seed germinates, it will be too late to put down the pre-emergent herbicide.

The other problem with spring lawn seeding for cool season lawns is that about the time the seed germinates and the grass seedlings begin to grow, the weather usually turns off hot and dry. Since the seedlings are new, they have not had enough time to produce good, strong roots needed to survive hot and dry conditions.

Another question that has been asked over and over is, "Should I control the weeds in my lawn first and then seed, or should I seed and then control the weeds?" The answer depends on the type of weeds you are trying to eliminate before you seed in the fall.

Grassy weeds that are annuals (crab grass, foxtail, etc.) should be left alone. When the first frost of the fall occurs, these grasses will die. You will treat your new lawn next spring with a pre-emergent herbicide to eliminate these weeds before they get started growing rapidly and competing with your new lawn.

Grassy weeds such as Johnsongrass and orchard grass that are perennials are a different story. They need to be treated with glyphosate about one to two weeks before lawn seeding. Glyphosate is a post-emergent herbicide that controls grassy and broad-leaved weeds, so it needs to be used before seeding. The two-week window will give the herbicide plenty of time to kill these grasses before you begin the seeding process.

When it comes to broad-leaved perennials such as dandelions, clover, etc., you should go ahead and seed and worry about these weeds later, for two reasons. First, during the seeding process, you will create the conditions conducive for dormant broad-leaved weed seed to germinate. So when you seed your lawn, and the lawn seed begins to germinate, so will the broad-leaved weed seed. Even if you kill every broad-leaved weed in your lawn before seeding, you will find you have more broad-leaved weeds in your lawn after seeding than you did before.

Wait until the new grass seedlings have grown enough to be mowed two to three times. You can then treat for broad-leaved weeds even in the new lawn. The new plants will be mature enough to withstand the broad-leaved herbicide.

Spray the broad-leaved weeds with trimec. This herbicide will not kill grass. It contains three different herbicides: 2,4-D, dicamba and MCPP. Be sure to use the amine form of this herbicide because it has low volatility. If you use the ester form of the herbicide, you may find that you get some burn on adjacent shrubs due to volatility.

If your new lawn contains broad-leaved weeds such as violets, use the herbicide triclopyr at the low label rate. This herbicide will control violets without damaging your new lawn.

We have had extreme weather conditions for lawns this year. We've had too much rain at times, and not enough at other times. These conditions have resulted in a proliferation of weeds and fungi in most lawns. You may want to take a hard look at your cool season lawn and determine if you need to do some reseeding. If you do, get on it as soon as possible. The earlier in the fall you get it done, the better your lawn will look late this fall and next spring.