If grass is yellow, the immediate question is whether the plant has died or if it is suffering from chlorosis, a lack of the green pigment chlorophyll. Yellowing turf signals stress, dormancy, or nutrient deficiency, but it is not a definitive sign of death. Understanding the difference between a temporary problem and an irreversible loss is the first step toward recovery, as viable grass can often be restored to a vibrant green.
Determining Grass Viability
The most reliable way to determine if yellow or brown grass is still alive is to perform a physical check. A gentle tug on the grass blades reveals the state of the root system. If the clump pulls out of the soil with minimal resistance, the roots have likely died, requiring reseeding or sodding.
If the grass offers firm resistance, the roots are still anchored, meaning the plant is likely dormant or severely stressed but viable. Examine the crown, the white or pale-green area just above the soil line where the blades meet the roots. A firm, white, or light-green crown indicates that the grass is alive and capable of new growth once the underlying stress is removed.
Primary Causes of Yellowing
If the grass remains viable, chlorosis results from an environmental or nutritional problem disrupting chlorophyll production. Identifying the exact cause depends on the pattern of discoloration and preceding conditions. A common cause is a deficiency in the macronutrient Nitrogen, a primary component of chlorophyll. Nitrogen deficiency typically results in a uniform, light-green or yellowing across the lawn, affecting older leaves first as the plant moves mobile nutrients to newer growth.
Iron Deficiency (Iron Chlorosis)
In contrast, a lack of the micronutrient Iron, known as iron chlorosis, presents differently because iron is an immobile nutrient. Iron deficiency causes pale yellowing in the newer, younger grass blades, often while the veins remain visibly green, a pattern called interveinal chlorosis. This issue is frequently compounded by high soil pH levels, specifically above 7.0, which can lock up the existing iron in the soil, making it unavailable for root uptake.
Water Management
Water management issues also trigger chlorosis and fall into two extremes. Under-watering, or drought stress, causes the grass to enter dormancy, turning it uniformly yellow-brown as a survival mechanism. Over-watering is deceptive; constantly saturated soil reduces oxygen available to the roots, hindering their ability to absorb nutrients like iron and nitrogen. This lack of oxygen can mimic nutrient deficiencies and create an environment conducive to fungal diseases.
Soil Compaction
Compacted soil is another underlying cause, restricting root growth and preventing the proper exchange of gases and nutrients. When the soil is too dense, water and fertilizer cannot penetrate effectively, leading to shallow root systems. These shallow roots are highly susceptible to drought and nutrient stress. A quick test for compaction involves seeing if a screwdriver can easily be pushed a few inches into moist soil; difficulty doing so suggests a need for mechanical intervention.
Targeted Recovery Strategies
Nutrient Correction
Addressing nutrient-based yellowing requires diagnosing the specific deficiency through a soil test. If nitrogen is lacking, applying a high-nitrogen fertilizer promotes a deeper green color and renewed growth. For iron chlorosis, applying a liquid iron supplement, especially a chelated iron product, provides a rapid, temporary green-up by bypassing the soil’s inability to release the nutrient.
For a longer-term solution to iron unavailability caused by high soil pH, elemental sulfur can be applied to gradually lower the soil’s alkalinity. Sulfur is often applied at a rate of around 5 pounds per 1,000 square feet in the spring and fall until the desired pH is achieved.
Water Schedule Adjustment
Correcting water issues involves adopting a deep and infrequent watering schedule to encourage deeper root growth. Instead of watering lightly every day, aim to apply about one-third to one-half an inch of water two to three times per week, allowing the soil to dry slightly between sessions. Watering in the early morning minimizes water loss from evaporation and reduces the time the grass blades remain wet, helping prevent fungal diseases.
Soil Improvement
To relieve compacted soil, core aeration is the most effective measure, involving a machine that pulls small plugs of soil from the ground. Aeration creates channels for air, water, and nutrients to reach the root zone, promoting a healthier environment for growth. This is optimally performed during the grass’s peak growing season, such as early spring or fall for cool-season grasses. If a thick layer of thatch exists just above the soil, dethatching may also be necessary to remove the barrier preventing water from reaching the soil.