The sudden appearance of brown patches across a lawn can be a frustrating experience for any homeowner. Sod is mature, transplanted turf, and browning is a common symptom indicating an underlying problem. This discoloration is frequently reversible once the specific cause has been identified and addressed. Determining the root issue requires a systematic inspection of the turf, soil, and surrounding environment.
Diagnosing Browning Due to Water Stress
Improper hydration, either too much or too little, is the most frequent cause of brown sod. Underwatering is indicated by a loss of turgor pressure; grass blades may first appear gray or bluish-green before turning yellow and then brown. A simple “footprint test” can confirm this: if your footprints remain visible for more than 30 minutes, the grass lacks the moisture to spring back immediately. The soil will also be dry and hard, confirmed if a probe is difficult to push down more than a couple of inches into the turf. Correcting this requires deep, infrequent watering to encourage roots to grow down into the subsoil, rather than shallow daily sprinklings.
Conversely, browning from overwatering or poor drainage often presents with a spongy or squishy feel when walking across the turf, indicating saturated soil. Excessive moisture suffocates the roots by displacing the oxygen they need, which leads to a yellowing of the grass blades before they turn brown. This condition is also a precursor to fungal development, as the constantly wet environment is highly favorable for disease organisms. Addressing overhydration involves reducing the frequency of irrigation, allowing the top layer of soil to dry out between waterings.
Identifying Biological Causes: Pests and Disease
If the browning is localized in irregular or circular patches and does not improve with adjusted watering, the problem may be biological, caused by insects or fungal pathogens. Grubs, the C-shaped larvae of various beetles, are a common pest that feeds voraciously on grass roots, effectively detaching the turf from the soil beneath. A telltale sign of grub damage is the ability to easily lift or roll back a section of the brown sod like a piece of carpet, as the root system has been severed. Finding more than five to ten grubs per square foot is considered an infestation requiring treatment.
Fungal diseases, such as Brown Patch, cause distinct browning patterns, often appearing as circular or irregular patches ranging from a few inches to several feet in diameter. In certain grass types, the disease creates a “smoke ring” or a doughnut pattern, where the outer edge of the patch is darker or more recently affected. This fungus, Rhizoctonia solani, thrives during hot, humid weather when grass blades remain wet for extended periods, such as after late-day watering. Reducing leaf wetness by watering in the early morning and ensuring good air circulation help manage the disease.
Environmental Stress and Cultural Factors
Browning is not always a sign of impending death but can be a natural response to climatic extremes or improper maintenance. Seasonal dormancy is a survival mechanism where grass halts growth to conserve energy and moisture during harsh conditions. Cool-season grasses, like fescue, turn brown in intense summer heat and drought when temperatures exceed 85°F. Warm-season grasses, such as zoysia or Bermuda grass, go dormant and lose color in the winter when soil temperatures drop below 55°F. The grass is merely resting and will green up again when favorable temperatures return.
Mechanical damage from mowing or chemical imbalance from fertilization can also cause discoloration. Scalping, which is cutting the grass too short, removes too much photosynthetic tissue, causing temporary browning and stress. Never remove more than one-third of the grass blade height in a single mowing session. Fertilizer burn occurs when excessive nitrogen salts draw water out of the grass blades, leading to streaked or patchy browning that is often crispy. This chemical dehydration can be mitigated by immediately applying a deep, thorough watering to flush the concentrated salts away from the root zone.