While it may be hard to believe, most weeds actually blow into your lawn as seeds and sprout the minute they find enough bare soil, moisture, and light to grow. This is true for both annual weeds and perennial weeds. Annual weeds sprout, grow, flower, seed, and die within one year. Perennial weeds sprout from a seed as well, but the weed plant continues to grow and spread for more than one season.
Unfortunately, all fescue lawns weaken during the hot Southern summers and a thinning lawn is the perfect place for a weed seed to germinate and grow. Consequently, your ultimate goal becomes to grow a thick lawn that will naturally crowd out weed seeds.
There are two ways to accomplish this. First, correct fundamental problems like shade, poor drainage, and soil compaction that make growing a thick fescue lawn difficult. Second, stay on top of lawn maintenance. Fescue lawns need to be nurtured during the hot summer and a couple of weeks without water or mowing can be devastating. Also, you will need to incorporate a weed control program into your yearly maintenance activities.
Types of Weed Control for Fescue Grass
Pre-Emergence weed controls: kill immature weeds immediately after they germinate and before they emerge from the soil surface. Since annual weeds like annual bluegrass and henbit die and return from seed each year, a pre emergence wed control will eradicate them from your fescue grass lawn over several seasons. At the same time, it will prevent annual and perennial weed seeds that blow into your lawn from emerging. Most pre-emergence products are sold in a granular from with or without fertilizer that you spread using a fertilizer spreader. If is important to spread the chemical wall to wall at the recommended rate. Areas that are not covered by the chemical will not be protected. After spreading the product, irrigate your lawn with at least .5 inches of water to activate the chemical (unless otherwise stated on the bag). Once activated, pre- emergence weed controls create a chemical barrier in the upper inches of your lawn that will prevent weed seeds from germinating. Do not cultivate, aerate, or disturb the soil after treating your lawn or you will disrupt the chemical barrier and open the soil to weed infiltration. Pre emergence weed controls are usually effective for 2-3 months, depending on the temperature and amount of rainfall.
Post-emergence weed controls: kill weeds that are already growing in your lawn. These products are referred to as "selective" since they are targeted at specific annual and perennial weeds listed on the label. Usually, controls will either treat grassy weeds like crabgrass or broadleaf weeds like chickweed. Choose the weed control spray that best suits your needs. You may need to purchase a spray for each category of weeds. In most cases, post emergence products are designed to disrupt one of the weed's critical metabolic processes and should be sprayed when the weed is actively growing. If the weed is dormant because of cold weather or drought it may not die. Post emergence products are most often sold in liquid spray. The liquid sprays are very effective when weeds are young and actively growing. Spray on a day when your air temperatures are 60 to 80 degrees and the grass is dry. Avoid spraying during the 4-6 weeks in the spring when your fescue grass is greening up. Post emergence weed controls are sometimes sold in granular form that is spread with a fertilizer spreader when the grass is wet. The dry particles need the moist to adhere to the weed leaves.
Another group of post emergence weed controls are the non selective sprays such as Round-Up. The term non-selective means they will kill all vegetation including Fescue grass. The trick is that non selective weed sprays are absorbed through plant leaves. During the winter months when your Bermuda grass is brown, you can carefully spray green weed without affecting dormant Fescue grass. WATCH OUT!
When to apply weed controls
When it comes to weed control in a fescue lawn, timing is critical. Pre-emergence weed control shave to be applied before weed seeds germinate or they are useless. Post-emergence weed control sprays and granules have to be applied when the weeds are young, tender, and actively growing. I have found that when it comes to weed control, it is always better to be a little early rather than a little late.
Under normal conditions, a well-grown fescue lawn will remain weed-free with two applications of granular pre-emergence weed control (late winter and early fall) and spot treatments of problem weeds in mid-winter and early summer.
Late winter: Apply a pre-emergence weed control without fertilizer when the soil temperature reaches a consistent 50°. This is usually February/early March, when Forsythia is in bloom. This application will control annual weeds and perennial weeds that germinate in the spring. Do not aerate for 3 months after you apply pre-emergence weed control because it will affect the chemical barrier. Irrigate after applying unless other wise instructed on the bag. Be sure not to use a pre-emergence weed control that contains fertilizer. If you fertilize now, you might stimulate your lawn to break dormancy during a warm spell, only to be damaged by freezing temperatures soon thereafter.
Spring and Summer: Begin treating weed outbreaks as soon as you see them with a post-emergence weed control spray approved for use on fescue. Weeds will die quickly when they are young and actively growing. Spray on a calm day when the air temperature is 60-80°. Avoid spraying newly seeded or sodded fescue, however, until you have mowed at least twice.
If your lawn is still overrun with weeds in mid-spring, consider using a combination fertilizer/ post-emergence weed control (granular form) when you fertilize in early April. Apply pre-emergence weed control without fertilizer 2-3 months after your late winter application to control the annual and perennial weeds that continue to germinate into the summer. This is usually around June 1st. If your lawn is mostly weed-free, you can skip this application.
Early fall: Apply pre-emergence weed control (without fertilizer) to fescue lawns when soil temperatures drop to 70°. This is usually mid-September in the upper south and late September in the middle South. Do not apply pre-emergence weed control if you are planning to seed, sod, or reseed your fescue lawn in the fall. It will prevent fescue seed from germinating.
Winter: (optional application). This is usually in late November/early December. If your lawn is mostly weed-free, and weeds do not usually blow in from surrounding areas, you can skip this application. Use a product approved for use on Fescue and apply at the rate recommended on the bag. Irrigate after applying unless otherwise stated on the bag.
During the winter, treat winter weed outbreaks as soon as you see them with a post-emergence weed control spray approved for use on Fescue. This is usually in January and February. Most of your problems this time of year will be from annual weeds like annual bluegrass and henbit. Spray on a warm after-noon (air temperature is at least 60°) when the weeds are young and actively growing. It may take two applications to kill them.