The latest fallout from June’s heatwave and dry, yet humid weather are black grass patches in lawns. I have not seen this phenomena for some time, a unique scenario caused by extreme exposure to environmental conditions…very rare and more typical of mid-July or August.
The black grass is decaying surface leaves that are likely caused by the combination of a disease called brown patch, intense heat and dry soil conditions – all prerequisites for this fungal disease to manifest itself.
Rain (or irrigation) and cooler temperatures are important to enhance recovery in these areas. Remember, we are looking at the dead surface leaves, not the living part of the plant (the crown) which is not visible at ground level. Recovery will be slow and dependent upon future rainfall or irrigation in combination with cooler temperatures, as continued drought and heat may affect the health of the black patches in the long term. It is difficult to say how much permanent damage has occurred until the lawn has the opportunity to recover. It may take until early fall to determine if there has been long-term thinning from this disease and/or from continued summer weather stresses such as high heat and lack of rainfall. Areas that do not fully recover by early fall may need aerating and overseeding at a minimum, to perhaps a spot renovations as a worst case scenario. Fortunately, fall is the best time of year for any kind of lawn seeding.
For now, don’t add stress by mowing, if possible for a period of weeks. Keep the affected areas moist, not wet and do so in the a.m. only, not late pm. Late afternoon and evening watering can exacerbate fungal diseases. It’s also important to water “hot spots” or tan areas of your lawn that have been, or are susceptible to drought and heat stress. And then, we just need to let nature take its course.