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Extension Disaster Education Network|University of Wyoming Extension

Horticultural Drought Tips

Drought

Roger Hybner (Formerly with the UW Research and Extension Center, Sheridan) and Karen Panter (UW Horticulture Specialist, Campus) put together the following tips on water conservation as it applies to maintaining lawns. Water conservation is sure to be a major issue this summer as we again face water shortages across the state.

For those of you who have not heard, Roger has recently seeded 176 different bluegrass varieties for long-term trials.

Irrigation

Clay soil holds water VERY well (almost too well) and needs less frequent irrigation.

  • water early in the morning
  • for automatic sprinkler systems, check them to make sure they are operating properly - not watering the sidewalk and driveway for example
  • thorough, deep watering's less frequently are better than frequent shallow watering's - after watering, dig down to see if water has penetrated to a depth of 6 to 8 inches - if so, you've watered sufficiently - if not, additional time may be warranted
  • check to see what the soil type is under the turf - sandy soil does not retain water well and will need more frequent
  • watch those "micro-climates" - around any structure there will be places where turf will dry out quickly and areas where it will stay wet longer - know where these are and tailor your irrigations accordingly
  • bluegrass will require about 2 inches of water per week under warm, dry, windy conditions - measure this by setting out a can or jar and then irrigate as you normally would - after irrigating, check the level of water in the container  and this will tell you how much you're applying at each watering
  • consider alternatives to bluegrass - buffalograss, some fescues, many types of groundcovers, as well as ornamental grasses can be used
  • mow high - 3 inches is recommended - this increases grass' tolerance to drought and insect/disease problems
  • when mowing, never remove more than 1/3 of the height of the blades at any one time - if you want 3" tall grass, mow when the grass is no more than about 4" tall
  • make sure your lawn mower blade is sharp - tattered grass blades will lose more water than clean cuts
  • avoid overfertilization - this will lead to lush, soft, tender growth that will not tolerate drought conditions well
  • core aerate each year - this helps keep root systems healthy.

Heat Stress:

Burned foliage on trees and shrubs doesn't necessarily come only from lack of water. Often new construction of light-colored fences and even the addition of aluminum or vinyl siding on a house near trees and shrubs can cause serious damage to existing plants. Alert consumers that any time changes are made in concrete areas, decks, siding, fences, or even removal of nearby trees and shrubs, existing plantings will be affected - usually for the worse.

The reason is that reflected heat and light from these additions cause the side of the plant nearest the change to be warmer and to transpire water more quickly than it did before. Unless the plants are protected by a barrier of some sort, the plant simply will not be able to take up enough water to compensate for the higher light and temperature load. And so the leaves burn.

Beware those Sunday newspaper ads:

Oftentimes Sunday papers will contain advertisements for plant materials that may sound good on the surface, but will not tolerate our climate. Recent calls have brought up this timely subject. The calls concerned an ad for zoysia grass, touted as hardy to -30F, drought tolerant, heat tolerant, easy to grow, and the greatest thing since sliced bread.

Unfortunately, the facts are not presented in the ad. Zoysia is a warm season grass that is only hardy as far north as zone 6...it is highly recommended for zones 6 through 10. We don't have any zone 6s in Wyoming. Zoysia is adapted to the southern part of the U.S.

Ads such as this are placed nationwide, without regard to local climates. We've seen ads like this for austrees, hydrangeas, and many types of fruit trees - most of which are not recommended here. Remember, buyer beware, and if the product looks too good to be true, it probably is!

Brown Evergreens:

We are seeing a rash of winter drought and frost injury, mostly on evergreens. This winter was a cold one and was preceded by a warm, dry summer and several warm, dry winters. If property owners did not water trees properly in previous years, count on seeing brown branch tips and possibly death of entire plants.

More Brown Evergreens:

Spruces and firs seem to be dropping like flies. Basically, several warm, dry winters followed by this year's cold, wet one have done evergreens in. Root systems were weakened by drought conditions previous to this year. Then, the recent cold winter was too much for some tree roots - many succumbed to the cold. This translates to brown needles and branch dieback on the above-ground portions of the tree.

The Right Tree in the Right Place:

For understandable reasons, people love to bring trees (and heaven only knows what else) from the mountains to their back yards. Aspens, spruces, firs, and other plants are too frequently dug out of the wild (with proper permits of course) and planted in urban areas. Unfortunately, this almost always leads to problems. Spruces, firs, and aspens prefer moist, slightly acidic soils and protected areas. Urban areas may be protected, but our soils are usually not moist and are almost always alkaline instead of acidic. Asking a tree to make the transition is a pretty tall order.

Think about where they grow in the mountains. Then think about the typical Wyoming urban back yard. Hardly similar.

Add to that the fact that most people do not know how to dig a tree properly, probably don't do much to protect the root system during transport, and may not even have the site prepared at the tree's new home. Talk about a stressed-out plant.

We recommend that people purchase trees from a reputable, local nursery staffed with knowledgeable employees. Commercially-grown plants will have been properly grown and cared for and will have a much better chance of growing and thriving in the urban landscape.

Use of Antitranspirants:

The proper use of antitranspirants has been a topic of interest lately. We recently saw a sample of spruce (we think) that was so covered with the stuff that it was sticky and the needles were glued together. No wonder the tree was in poor health.

According to Richard Harris, James Clark, and Nelda Matheny, authors of "Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines" (1999):

"Sometimes leaves are stripped off or antitranspirant sprays are applied to plants in leaf to reduce transpiration during and after moving. The species sprayed and the concentration of antitranspirant applied must be carefully chosen. Antitranspirants seem to be more toxic to evergreens than to deciduous species. Used with caution, the sprays may reduce water loss not only during the growing season but also during the winter for conifers and other evergreens."

There are several types of antitranspirants:

  • some are reflective materials that reduce absorption of radiant energy (heat), lowering leaf temperatures and reducing transpiration
  • some are emulsions of wax, latex, or plastics that dry on the foliage and form thin films that minimize escape of water from the plant
  • some are chemicals that "affect the guard cells around stomatal pores and prevent stomata from opening fully, thus decreasing the loss of water vapor from leaves."
There are drawbacks to each of these. The reflective materials leave a colored coating on the plant that may not be aesthetically acceptable. These also reduce light penetration into the leaf, reducing photosynthesis. The spray emulsions reduce water loss, but they also reduce carbon dioxide intake into the plant, thus reducing photosynthesis. The chemicals that keep stomata from opening seem to allow more carbon dioxide in than water vapor out, so seem promising.

The authors suggest that "repeated application can retard growth by seriously reducing photosynthesis. Even so, film-forming materials are the most commonly used antitranspirants and have a place when reduced transpiration for a few days to 2 weeks is crucial."

Antitranspirants are tools in helping plants endure stressful, short-term periods. They are not panaceas or replacements for adequate watering of plant material or proper plant selection.

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