The ideal lawn looks like a lush, emerald carpet. To achieve this, you water and fertilize your lawn religiously, mow to a specific height on a regular schedule, aerate and overseed in the spring and keep a sharp eye out for any signs of trouble. So, why do you see a yellow-tinged lawn instead of that brilliant green you're striving for? And more important, how do you turn a yellow lawn green?
One possible answer may surprise you: too much lawn care. Overwatering and overfertilizing can both lead to yellowing and browning lawns. However, if you see patches of yellow, dying grass dotted throughout the yard, another problem may exist. Accurately identifying the cause is the first step in turning your yellow lawn green again.
Incorrect Watering Causes Yellow Grass
A dry, brittle, brown lawn definitely needs water to survive and turn green. But overwatering can also lead to yellowing because it causes a nutrient imbalance that causes the green chlorophyll cells to die.
Roots require oxygen gas in order to function. Just as people can't breathe under water, roots can't retrieve oxygen from water. Grass roots essentially drown when they're constantly wet from overwatering. When the roots can no longer take in oxygen or important nutrients from the soil — like nitrogen or iron — the blades begin to turn yellow.
If this is the problem, the solution is simple: skip watering for a little while until the soil dries up. You should see the green color return to the grass once the roots can breathe and begin to transport nutrients again.
Nutrient Imbalances Cause Yellow Grass
Nutrient imbalances can occur in lawns even when you don't overwater. According to the University of Maryland Extension, lawns typically require an annual application of nitrogen fertilizer. Otherwise, yellow streaks can appear in the blades. Iron deficiency can also cause yellow streaks.
For best results, use a soil test before purchasing a fertilizer so you can apply the correct type. Too much fertilizer is just as problematic as no fertilizer. Pennington points out that "fertilizer burn" occurs when grass gets overloaded with fertilizer, which is why it's important to apply fertilizer at the manufacturer's recommended rate and avoid overlapping your applications.
To help your lawn recover from too much fertilizer, water the area deeply. This helps to flush out the nutrients. Interestingly, animal urine also causes yellow spots due to its high nitrogen content. The repair technique is the same: rinse the area with water as soon as possible.
Causes of Yellow Patches
Diseases affecting grass typically appear as yellow patches in the lawn. Overwatering and overfertilizing are often implicated in the presence of diseased grass because they weaken the plant's ability to fend off disease. Many fungi in particular thrive in soil that's constantly moist.
The University of Georgia Extension notes that brown patch, dollar spot, pythium, helminthosporium leaf spot, fading out, take-all root rot and rust are all examples of turfgrass diseases that tend to appear when there's a nutrient imbalance or water stress. In most cases, the issue can be corrected with proper watering and fertilizing techniques. For faster results, fungicides may help as well.