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Managing Landscape Turf under Heat and Drought Conditions

July 29, 2011
by Grady Miller

NC Drought Map 
NC DROUGHT MAP
July 26, 2011

The US Drought Monitor of North Carolina (http://www.ncdrought.org/) currently has approximately two-thirds of the entire state in some level of drought. The southeastern part of the state is currently under extreme drought. Worsening the problem is the above average temperatures. High temperatures cause cool-season grasses like tall fescue to photorespire. This results in a heavy energy toll on the plant. Heat alone is generally not problematic with warm-season turfgrasses unless there is low soil moisture.

There are two current issues to consider: irrigation to maintain your current grass and renovation of cool-season turf areas this fall. Depending on your irrigation capacity and current level of irrigation restrictions you can either irrigate to maintain growth and green color or irrigate for turf survival, allowing the turfgrass to go semi-dormant to dormant. Turf survival under drought conditions is affected by turf species, turf age, rooting depth, soil type, shade, maintenance, traffic, heat, etc.

Common recommendations indicate that turf this time of year needs approximately 1 inch of water per week from irrigation or rainfall. This is an approximate amount to irrigate if you want to keep the turf green and growing. Set your controller to water between 10:00 pm and 8:00 am to improve efficiency. If you pull water from a city water system and have low water pressure, it is typically better to water at night rather than early morning when the water demand is high. Check your irrigation system for evenness of distribution and put out a few catch containers to verify the application rate (amount). You can fine tune the application by not watering again until you see turf turning bluish-gray in the heat of the day. If you are under water restrictions, then you may need to hand water those areas that show visual signs of heat and moisture stress until your next allowed irrigation.

If you decide to minimally water, then use ½ inch of water every two to four weeks to keep the turf crowns hydrated. This amount will not turn the turf green, but it will increase its chance of survival. Avoid herbicides and fertilizers until rains resume. Also, keep vehicle traffic (e.g., riding mowers) off the turf when it is under severe drought stress.

If you have not irrigated nor received any rainfall in months, the turf stand will likely be severely thinned this fall. The normal time for fall renovation of tall fescue or tall fescue/Kentucky bluegrass lawns in most of NC is early September. So, if your yard is currently thinned due to drought stress, the period of time to begin renovation is just several weeks away. Hopefully by then we will be back in a more normal rainfall pattern and a fall renovation will have your landscape looking as good as new.

If you have a warm-season grass such as zoysiagrass, bermudagrass, centipedegrass, or St. Augustinegrass, they will generally be able to handle dry conditions better in terms of survival, but they may still be severely damaged from chronic drought. The time to renovate warm-season grasses is normally in spring/summer. Once temperatures begin to subside, you may see some recovery this fall. Note that warm-season grass sod can be installed in fall, although it may be more susceptible to winterkill.