Anyone familiar with the color wheel understands how closely green and yellow are related and in a lawn setting the grass is no different.
You can’t make green without yellow, the two colors are considered analogous and create a beautiful composition together, but when it comes to your lawn you don’t want to look outside and see yellow grass. You want to see lush, green grass throughout the yard.
That being said, let’s talk about the common reasons why your lawn turns yellow so that we can fix any problems before they get worse.
There are a handful of reasons your grass yellows. Sometimes, a single reason causes the color change; sometimes, the culprit is causing a cascade effect of issues, and yellowing is an indirect result.
Underwatering – A lack of water is one of the most common reasons for yellowing. Water is needed for photosynthesis, but it also facilitates the uptake of nutrients from the soil into the roots.
Nutrient deficiencies – Plants need specific nutrients for growth. If the soil is deficient in nutrients — especially nitrogen or iron — yellowing occurs. Nitrogen is an essential component of chlorophyll, and iron is a constituent of the enzymes that produce chlorophyll.
Over-fertilization – Nutrient toxicity also causes yellowing grass, especially if nitrogen is over-applied via synthetic fertilizer products. Too much nitrogen, urea specifically, directly damages the roots and impacts nutrient and water uptake. High nitrogen can also alter the soil pH and affect nutrient availability.
Diseases – Lawn diseases often lead to yellow grass or dead patches. The most common problems are fungal: brown patch, dollar spot, rust disease, Fusarium patch, and snow mold.
Too much water – Overwatering fills the pore spaces between soil particles with water, pushing oxygen out of the root zone. This lack of oxygen, in turn, reduces root function or causes them to rot. In turn, the roots struggle to take in nutrients, oxygen, and water.
Pets – Homeowners with pets often see yellow spots since dog urine contains high levels of nitrogen compounds.
Pests – Soil-borne pests may eat through the roots, impacting water and nutrient uptake. Sap-sucking insects may cause yellow spots where they feed or introduce disease(s) into the plant when feeding on nutrient-rich sap.
Accidental chemical spills – Spilled lawn chemicals are an often overlooked cause of yellowing. Common culprits are concentrated insecticides or fungicides, but significant amounts of fertilizer or weed killer in one spot can also be at fault.
Soil compaction – If the soil in your yard is compacted, water movement down into the root zone is reduced, causing a lack of water in the ground.