HUTCHISON, Kan. — Excessively high temperatures and very little rainfall are putting landscapes at risk from the central to southern plains.
“We’re getting a pretty drastic lesson in why we’d do well to plant native or other drought-resistant plant materials. Cold hardiness isn’t enough. We also need to be learning how we can get the most out of the water we have available. If we’re lucky, maybe we won’t have to limit our soap use, so we can recycle our bathwater outdoors on our dying plants,” said Pam Paulsen, K-State Research and Extension horticulturist.
During a drought, the most vulnerable plants are those that don’t have a well-established, deep root system, Paulsen said. This automatically includes all recent transplants and all container plants. In fact, depending on how dry and hot the weather is, Kansas container plants sometimes need twice-daily watering, just to survive.
“Typically we recommend watering early in the morning. That’s when you’re least likely to lose irrigation water to evaporation,” she said. “Plus, the day’s rising temperatures will help foliage dry out quickly, reducing the risk of foliar diseases.
“When plants are under severe drought stress, though, watering as soon as possible minimizes further damage – regardless of the time of day. It’s a myth that water droplets on foliage will magnify the sunlight and burn plants. What is true is that puddled water where soil doesn’t drain readily can heat up and ‘stew’ plants.”
From spring into fall, plains landscapes need an average inch of moisture per week, supplied by rainfall and/or irrigation, Paulsen said.  Some landscapes can need more — particularly where soils are sandy, plants are semi-tough non-natives, soil is bare, and/or temperatures are extremely hot.   Extra watering also can be necessary in times of low humidity or high winds.
“Those exceptions also can affect how often you should water,” she added.
In general, perennial plants, lawns, shrubs and trees do best if watered deeply and infrequently. On average, about once a week is often enough, except during extreme summer weather, the horticulturist said.
This approach encourages plants to send roots deeper into the ground. The plants seemingly become more drought-tolerant because they can access soil moisture that’s available well below the surface level.
The best timing also can have exceptions, however, and not just ones that call for watering more often.
For example, if watered deeply enough, mature, healthy trees can actually go several times longer between drinks in typical Kansas summer weather, she said.  Even Kansans’ favorite cool-season lawn turf — tall fescue — can often survive without water for up to a month at a time. It goes dormant, so doesn’t look too nice. Still, a monthly soaking typically will keep the grass plants’ crown from dying.
“Other than that, a 2- to 3-inch blanket of organic mulch will shade the soil surface in planting beds and around trees. This shade will help moderate the soil’s temperature and reduce its moisture evaporation rate,” Paulsen said. “Rock and rubber mulches aren’t as good in hot weather, because they can really warm up. They also retain heat quite a while.”
She advises homeowners to remember how time- and energy-draining yard work can be during hot, dry weather.
“You’re going to more likely water as often as you should if it’s easy,” Paulsen said. “For example, think about strategically placing soaker hoses, sprinklers or drip irrigation systems. You could even leave them out where they’re always ready to go. If they’ve got snap-on connection valves, you can easily use them alone or in combination. You could even link them to an automatic, programmable timer connected to your faucet.”
To prepare for future water-scare times, she said, some possibilities are to:
1) Use free water to irrigate. Collect your roof’s downspout runoff in rain barrels during the growing season.
2) Use yard slope and landscaping ideas (baffles, decorative rocks, mounds, etc.) to slow down any runoff from rain or irrigation, giving your yard more time to absorb all the moisture it can.
3) Whenever you can, apply this principle: Incorporating organic matter improves soil’s water-handling ability – no matter whether the soil is heavy clay or fast-draining sandy loam.
“Organic mulch helps because it decays over time. But, you can make a much bigger difference in beds you till every year, because you can incorporate small pieces of organic materials at the same time,” Paulsen said. “Any fall garden debris that you can mow and catch in your grass catcher – leaves, dead annual plants, whatever – is great for that.”
K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans.  Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and research centers statewide. Its headquarters is on the K-State campus in Manhattan.