What’s the hottest yard and garden topic this summer? It’s not tomato blossom end rot, which is a distant second.
The issue that’s been on nearly everyone’s mind is how to care for lawns during a persistent drought. Crunchy brown grass was everywhere this summer, parched by heat and lack of moisture. Recent rains have given us hope, along with greener grass. Could the drought be ending, and where do we go from here with lawn care?
Increased moisture across the region has given us a glorious window of opportunity to repair our lawns in September. But winter is just around the corner, and we need to make every moment count.
For better understanding, let’s back up a moment. Kentucky bluegrass, which is the predominant grass in lawns across the Upper Midwest, has the wonderful ability to go dormant when summers turn hot and dry. It’s a self-preservation technique in which grass survives on stored energy reserves until weather conditions improve. Instead of dying when moisture isn’t available, grass remains alive, although brown and dormant.
Lawns can’t remain dormant indefinitely, and grass requires occasional small amounts of moisture, even while dormant and brown. About a quarter inch is needed once per month to keep the grass roots and crowns hydrated and alive. If that minimum moisture isn’t received, grass can pass from dormancy to death, from which there’s no return.
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How long can lawns remain dormant? Based on previous droughts, lawns can’t remain brown and dormant throughout both summer and fall and be expected to survive winter.
After a summerlong drought, lawns must be brought out of brown dormancy by early September, so grass begins active, healthy green growth. This growth is essential to replenish and rebuild grass’s internal energy supplies through photosynthesis before going into winter.
Luckily, much of the region received generous rainfall during the past two weeks. Accompanied by cooler temperatures, many lawns received enough moisture through the period to wake from dormancy. Grass has become active, green and growing.
Green grass is refreshing to see, and a window of opportunity has opened. We can keep this ball rolling and revitalize our lawns during the month of September by following these guidelines.
- To continue recovery, lawns that have emerged from dormancy will need moisture of about 1 inch every seven to 10 days, either from rain or irrigation, and preferably at one time so it penetrates into the root system.
- If the coming weeks turn hot and dry, lawns should not be allowed to go back into drought-induced dormancy. If rains don’t continue, lawns should be watered, if possible, until October to keep grass actively growing.
- To provide nutrition for rebounding grass, lawns that are green and growing should be fertilized around Labor Day. For lawns that are still brown and dormant, delay fertilizing until regrowth has started. Fertilizer can damage dormant lawns.
- Fertilizers sold in fall typically have higher rates of potassium, which is the third of the three numbers on the fertilizer bag, for increased root and shoot growth.
- Mow high in September. Set the mowing height at 3 inches, which provides more leaf area for photosynthesis and energy building. Lawns mowed low will have greater difficulty recovering fully from drought. Mowing height can be lowered for the season’s final mowing in late October.
- Kentucky bluegrass has the ability to spread sideways by its vigorous underground rhizomes, meaning it can fill blank spaces in the lawn. If there is a green grass spear every 2 inches or so, the lawn will fill back solid if given moisture and fertilizer.
- Thin lawns can be overseeded, if desired, with a mix containing at least 50% Kentucky bluegrass cultivars. If seeded before Sept. 15, grass will establish before winter. Gently rake the areas, sow the seed and lightly rake the seed into the soil or thatch. Keep surface continually moist throughout the germination period until new seedlings are highly visible.
- Weeds flourish in drought-stressed lawns. September is the best month for weed control, because weeds are carrying material into their root system for winter storage, and they’ll carry herbicides along as well. Liquid herbicides are recommended, which are more effective than granular weed-and-feed products. Spot-spray weeds instead of applying chemicals where no weeds exist.
- September is great for core aerating lawns, which removes small plugs of soil and thatch, opening air pockets in the soil and encouraging root growth, which helps lawns recovering from drought.
- Heavy duty power-raking or dethatching might be too vigorous for delicate lawns that are still recovering. Gentle raking or core aeration are probably better options.
- Some lawns or areas within a lawn might be dead. If no small green grass spears are emerging from the turf after two weeks of moisture and cool temperatures, reseeding might be the best option.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at donald.kinzler@ndsu.edu.
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