It seems that every year we experience a period of drought or heat that adversely affects the grass in our yards. Our regionally adapted grasses are prepared for this onslaught. Grasses have the ability to go dormant for differing lengths of time depending on their genetics and overall health.
Dormancy is a mechanism that grasses use to avoid conditions where inadequate moisture is available for growth. The most noticeable aspect of dormancy is the brownish-tan color of the leaf blades. This often occurs under drought conditions and during colder months.
Most established turfgrass can stay in a drought-dormant state for 3-4 weeks without dying. If the drought goes beyond 4 weeks, it’s recommended to rehydrate the lawn with deep, infrequent watering early in the day. Daytime temperatures in the 80’s (F), lawns can survive for 3-4 weeks, whereas climates in the 90’s reduce that survival time frame to 2-3 weeks. Irrigate lightly, about ½ inch, every 3-4 weeks to help your lawn get through the hot and dry summer months. Watering will not totally green up the grass, but will keep it alive. Infrequent and deeper watering prior to drought will develop deeper roots, which make plants much more sustainable.
During drought induced dormancy, turf will grow at a much slower rate and in turn will not require frequent mowing. Taller cut grass will have deeper, more extensive root systems than short cut grass which will help the turfgrass to withstand summer stress. If you need to mow, follow the one-third rule, never remove more than the top 1/3 of the blade at each mowing. To help minimize stress to the leaf blade ensure your mower blade is sharp.
During a dormant phase caused by heat or drought, an application of fertilizer will not bring a lawn out of dormancy. The turf is not growing because the roots have in essence shut themselves down. Once growing conditions are favorable with adequate moisture and tolerable air temperatures, the roots will be ready to take up nutrients from the soil. An application of fertilizer at this time is acceptable. Milorganite is one of the few fertilizers that can be applied during drought conditions. The salt free formula will not burn the turf, and the nutrients will remain in the soil profile until conditions become favorable for root uptake.
Cooler temperatures can send both warm and cool season turf into dormancy. Cool season turf endures cooler weather better than other types of grass and typically begins to go dormant in the fall once soil temperatures drop to 50 degrees. Warm season turf can tolerate extremely warm temperatures and have a very low tolerance for cold weather. Warm season turf will typically begin to go dormant around mid to late October. Keep in mind that an application of fertilizer will not bring turf out of dormancy, however this is the most important time of year to fertilize. You’re not feeding the grass for the growth above ground, you’re building up food reserves so the grass will go into the winter strong and green up faster in the spring.