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Why Does Grass Turn Yellow?

There are many potential reasons that you will see yellow grass in your yard. At one time or another, most homeowners will experience yellowing grass. Here are a few reasons things that can make your green grass turn yellow, plus a few solutions and tips for fixing them.

Too Much Fertilizer

Using too much fertilizer can cause your grass to be yellow when it's supposed to be green. Severe over-application can even cause the grass to die. This is especially true when you use synthetic materials. Fertilizer applicators require specialized training. The technician must complete the Florida Friendly Best Management Practices for Protection of Water Resources by the Green Industries Program. The technician must also pass a competency test. Each person applying fertilizers must complete this course; one person in the company cannot qualify the others. In this author's experience, most lawn maintenance companies do not have this credential. For properly calibrated fertilizer applications applied according to the BMP guidelines by certified technicians for your West Palm Beach home, call us at 561-791-2400.  

The Fix:

  1. Remove any excess fertilizer.
  2. Make sure to give the area adequate water.
  3. If the grass ends up dying, plant new grass as described below.
  4. Wait two weeks before replanting.
  5. If the area is small and we are in the cooler months, you can overseed with Ryegrass to allow the turf to fill back in.
  6. If it is in the Spring or Summer, replace the area with new sod.
  7. If you leave the area bare for an extended period, weeds will fill the void.

Why Does Dog Urine Damage Grass

Chemistry is why dog urine turns grass brown or yellow. Understanding why this happens is your first step toward preventing it and maintaining a green, healthy turfgrass.

Nitrogen is a primary component of healthy soil, but unusually high concentrations can cause grass patches to turn yellow or brown and die. Urine is naturally rich in nitrogen, and high nitrogen concentrations can cause grass burns. Lawn fertilizer contains nitrogen as well. Frequently the dead grass is surrounded by an exceptionally lush, green ring of growth, which occurs due to the fertilizing effects of lower concentrations of nitrogen around the edges.

Salts and other compounds in dog urine may also help promote damage to the grass. Exceedingly acidic or alkaline urine may alter the pH of the soil, adversely affecting the grass in the areas of the yard where your dog urinates.

There is a school of thought that female dog urine causes more problems to the lawn than male dog urine. Notwithstanding, the chemical composition of the urine doesn't differ much between male and female dogs. The difference is that the way the dogs urinate is not the same. Female dogs can cause more damage to grass because most tend to squat and urinate in one place; many males lift a leg and "mark" upright objects in multiple locations. For instance, when a male dog pees on a tree trunk, only some of it may drip down to the grass and cause damage. The male method is less noticeable than the round spots of damaged turf made by female urine puddles.

The Fix

You can help prevent brown and yellow spots on your lawn caused by dog urine. Although there's not a sure-fire way to end urine spots in the yard, you can take steps to minimize the damage.

  1. Train your dog to urinate in one area to reduce the portion of the lawn that's affected. Fence a part of your yard, so your dog only goes in that one area. You can camouflage this spot with plants like tall grasses or low bushes, so it's less visible from other parts of the yard.
  2. Create a turf/plant-free area by covering the dog's potty area with mulch. This type of ground cover makes picking up after Fido easier as well.
  3. Increase your dog's water intake. Dogs should be taking in a lot of water to maintain their health anyway, and the extra water may dilute your dog's urine enough to reduce the nitrogen below the threshold where grass damage occurs. Of course, this approach likely means that your dog will have to urinate more often, but the benefits may outweigh the inconvenience. Be sure to run this by your veterinarian before changing your dog's diet.
  4. Use a garden hose to rinse off the area after your dog urinates immediately. Encourage your dog to urinate in different places if you do not have a designated or mulched area.
  5. Keep in mind that other animals might have access to your yard, and their urine can also cause lawn damage. A fence will keep out any dogs passing by, but cats and various wild animals are not so easy to stop. This may explain why you continue to see brown or yellow spots in the yard after trying everything with your dog.

Soil Compaction

Compacted soil can cause all sorts of turf issues. Major culprits are vehicles, construction vehicles, foot traffic, and lawnmowers following the same pattern week after week. Compaction squeezes pore space between the soil particles, which causes a decrease in the availability of air, nutrients, and oxygen to the roots and saturation of the pores with water. When that happens, your grass suffers and can turn yellow.

The Fix:

  1. After winter has passed is the perfect time to aerate your St. Augustine grass in South Florida. Hire a professional or rent a core aerator for around $65-$85/half day.
  2. Before aeration, it is best to moisten your grass for this particular type of grass and then use a hand rake to remove the thatch. Thatch is the layer of organic plant matter that settles at the base of the grass and should be raked away once your grass is no longer dormant. After you have dethatched, the next step is to rent a core aerator from your local hardware or garden store. This is the best option because it will result in larger, deeper plug holes and opening access to the root. Most aerators will include a renters user's guide; however, the operation of a core aerator is similar to that of a push-type mower. Aerate when the soil is moist, not wet. Soft ground allows for deeper penetration of the coring tines. Make several passes over the yellow grass, punching as many holes in the area as possible. Don't worry; you won't harm the grass by aggressively aerating. Keep going until you see at least 12 holes per square foot of lawn.
  3. The process of aeration results in small divots and plugs lying over the yard. That is perfectly normal. It is best to allow them to naturally break down over time because this provides the grass with an organic source of nutrients. The yard will not look its best right after aeration, but the long-term benefits are well worth it.
  4. After they have dried, gently break up the cores and work them back into the grass. 

Spilled Chemicals

Weed killers must be applied precisely to the target site. Accidentally spilling a weed killer on your lawn when filling your hand sprayer will often kill your grass. Ever notice a dead ring around the edges of a flower bed after you applied material like Roundup to control weeds in the bed? Overspray during windy conditions to the unintended turf area will cause this damage. Acting quickly can minimize the damage.

The Fix:

  1. If possible, soak up any remaining liquid on the surface by applying highly absorbent materials such as kitty litter or sawdust. Place in a plastic bag and dispose of properly.
  2. You may be tempted to flush the spill area with water. Don't! Flushing the site will only worsen the problem by spreading the chemical over a larger area or, worse, down the storm drain.
  3. You'll want to dig out the contaminated soil to a depth of six to 10 inches. How deep you need to excavate will depend on how deep the pesticide soaked into the ground.
  4. Backfill the hole with weed-free soil.
  5. Re-sod the area. 

Grubs and Turf Damaging Insects

Royal Palm Beach is home to many turf-damaging insects. Grub infestation can result in the yellow grass. These tiny c-shaped "worms" (the larvae stage of many beetles) chew away at grass roots, severing them from the blades of grass above ground. Like chinch bugs and sod webworms, other insects can feed on grass blades rather than the roots, killing your grass from the top down. Both grubs and surface-feeding insects can kill or severely damage your lawn, turning it yellow.

The Fix:

Hire a professional who understands the turf-damaging insects in Wellington. Each new season also brings insects, disease, and weather problems that can damage or even destroy the beauty and health of your landscape. We promptly monitor and treat insect activity throughout each season to prevent long-term damage. Professional service means you can count on a carefree, beautiful, and healthy lawn throughout the entire year. Call us at 561-753-7777 for a free 25-point evaluation.

Too Much or Not Enough Water

Too much or not enough water can turn your lawn yellow or straw-colored. Too much water can drown grass roots and rob the soil of oxygen and that lush green color. Too little water will create drought symptoms that turn your lawn yellow or some shade of brown.

The Fix:

  1. Pay attention to the amount of water your lawn gets. That's easier to do if you run an automated irrigation system. You can adjust the frequency and amount of water to fit weather conditions and seasonal needs. The objective is not how long you water but the volume the roots receive. Frequent, shallow irrigation is significant in thinning, shallow-rooted, yellowing turf grass. In general, homeowners should follow the following principles for healthy turf.

     2. To compensate for rains, a rain gauge shut off system should be used. Two irrigations, if no rain, per week is all that is necessary. Each irrigation cycle should be 45-60 minutes each. This is designed to apply ¾-1" of water per cycle and wet the soil to a 10-12" depth. This allows for deep root development and more rapid leaf decomposition. It aslo provides for  better oxygen transmission to the root zone and inhibits competition from wet loving weeds e.g. Dollar weed, and Centella.  

Improper Mowing

Improper mowing contributes to several problems in turfgrass maintenance. The correct mowing height for St. Augustine grass is 3 1/2 -4". The frequency of mowing should be that never more than 1/3 of the blade area is removed at one time. This generally requires a mowing frequency of every 6-7 days during the growing season. 

When mowed too short, the grass will have a yellowed scalped look. Otherwise, the grass is put under greater stress, thatch build-up results in poor root development, and stolen root down is impaired. Mowing should only be done with very sharp blades for a clean cut. Frayed blade tips contribute to higher disease infection and plant stress.

The Fix

Mow your grass with sharp blades at the proper height and mow it frequently enough that you never remove 1/3 of the blade at any one time.

Bugs don't stand a chance! —Fernando B.
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