The appearance of dark green patches in an otherwise uniform lawn is a common issue that disrupts the aesthetic consistency of the turf. These areas of hyper-stimulated growth or different grass types stand out sharply because the grass blades contain a higher concentration of chlorophyll, making the color deeper and often the texture more lush. The goal of addressing these spots is to accurately diagnose the source, apply a targeted remedy to slow the localized growth, and ultimately blend the area back into the surrounding turf.
Pinpointing the Cause of the Dark Green Areas
Diagnosis begins with a careful observation of the patch’s characteristics, as the shape and location can strongly indicate the cause. Small, concentrated circles, often one to three feet in diameter, are typically the result of a concentrated nitrogen source, such as pet waste or a fertilizer spill. These spots may feature a dead or scorched center surrounded by the dark green ring, particularly with pet urine.
Texture is another important diagnostic clue; if the grass within the patch is noticeably thicker, taller, or forms a distinct clump, it suggests an invasive grass species or weed. A different leaf width or growth habit indicates that the problem is botanical rather than purely nutritional. Observing the patch’s location can also help; dark green rings near a tree stump or old buried wood may point toward fungal activity, while patches near walkways or downspouts could be caused by nutrient-rich runoff.
Remediation for Nitrogen-Related Overgrowth
The most frequent cause of a dark green patch is excess nitrogen. Pet urine spots are a common source, as the high concentration of urea nitrogen and salts can initially burn the grass, leaving a dead spot, but the surrounding area absorbs the diluted nitrogen and exhibits hyper-growth. For fresh pet spots, immediate and deep flushing with water dilutes the nitrogen and prevents the initial burn, minimizing the subsequent dark green ring.
When granular fertilizer is accidentally spilled or unevenly applied, the resulting dark patch is usually larger and more irregularly shaped. The first step is to remove any visible granular fertilizer before it dissolves, using a broom or shop vac. Following removal, the area must be thoroughly flushed with water, applying at least an inch of water daily for several days to dissolve and leach the excess salts and nitrogen deeper into the soil profile. This process slows the grass’s nitrogen uptake, allowing its growth rate to normalize and blend with the surrounding turf.
Addressing Patches Caused by Specific Plant Types
Patches that are dark green because they are a different species of plant require a botanical approach. Certain common weed grasses, such as clumping Tall Fescue or perennial Ryegrass, are naturally a deeper green and have a coarser blade texture than the desired lawn species. Because these plants are structurally different, they cannot be blended in through fertilization, and the most effective treatment is targeted removal.
Small clumps can be dug out, ensuring the entire root system is extracted, and the area can then be reseeded with the correct turf species. For larger infestations, a non-selective herbicide containing an active ingredient like glyphosate must be spot-applied directly to the undesirable grass, allowing for localized destruction without harming the entire lawn.
Another biological cause is the Type 2 Fairy Ring, a fungal phenomenon where fungi decompose organic matter deep in the soil and release concentrated nitrogen, creating a dark green circular band of grass. Treatment involves aerating the affected ring with a garden fork or core aerator, followed by a heavy drenching of water and a wetting agent to break the hydrophobic fungal layer and disperse the concentrated nutrients.
Techniques for Lawn Uniformity and Recovery
Once the cause of the dark patch has been addressed, the focus shifts to blending and prevention. To diminish the visual contrast, a light application of a balanced, slow-release nitrogen fertilizer can be applied to the surrounding, lighter turf. This strategy raises the overall nitrogen level of the lawn slightly, stimulating growth and deepening the color of the adjacent grass to match the previously darker patch.
Adjusting cultural practices can also minimize the appearance of color differences, especially by raising the mowing height. Taller grass blades present a larger surface area for chlorophyll production, leading to a deeper green color across the entire lawn, which makes localized differences less noticeable. Prevention involves maintaining a consistent fertilizer application schedule with a calibrated spreader and immediately soaking any areas where pet waste occurs to dilute the high nitrogen concentration before it can cause burn or over-stimulation.