Hydro-zone Your Landscape

Xeriscaping does not limit plants to low water-use, but it does promote conservation of water through creative and effective landscaping. Hydro-zone your landscape into water-use areas. This simply means to group plants together according to their water needs.

• Low water-use areas include adaptables and natives to our area (not necessarily native to Texas) that experience the same low rainfall without supplementation from underground sources such as a spring, creek bed or bog.
• Medium-water use plants include trees, favorite perennials promoted for East Coast and Southern gardens, specialty plants, and many Great Plains plants that naturally grow in areas receiving higher annual rainfall.
• High-water use plants are bluegrass and tall fescue lawns, vegetables, some ornamentals and heat loving plants from rainier climates. Some common examples are pansies, caladiums and elephant ears to name just a few.

Landscape Design, Turf Care, Appropriate Maintenance Aid in Water Conservation

• Design lower water-use buffer zones into your landscape. Narrow strips, such as the hellstrip – the area between the sidewalk and street—are more suited to low water-use plants. Concrete and asphalt reflect a great deal of heat and dries out the soil quicker. Likewise, areas to be landscaped next to brick, metal and concrete structures and any areas 10 feet wide or less are more difficult to irrigate efficiently. These buffer zone help prevent water falling on concrete due to wind drift.
• No matter what type of home irrigation system you have, avoid watering the concrete for water conservation. We are all guilty of this misplacement of water. There aren't enough calm days available when we need to water; another reason to install drip irrigation.
• Design the landscape by placing high water-use zones to maximize water from roof-runoff, if you haven’t installed a roof water catchment system.
• Spacing: if water supplies are critical, space plants further apart, mulching in between. Remember, each plant requires a set amount of water for survival. Packing more plants into a given space requires more water than spreading them out.
• Mounds in lawns (for visual interest) require more water than lawns on a flat area; avoid lawn berms and mounds.
• Appropriate turf maintenance conserves water. Mow high, more frequently. The higher the grass blades, the more shaded the root zone. Mowing high, more frequently encourages deeper root growth. Mowing with a mulching mower adds the grass back providing nutrients and moisture from the clippings, reduces evaporation and moderates soil temperature. Aerate the lawn once a year in early spring.
• A general suggestion is to limit high water-use plants to 1/3 of the landscaped area (lawns and vegetable gardens). For highest water efficiency, use buffalograss and blue grama turf grasses instead of bluegrass and fescue. Substitute low water-use groundcovers in place of turf. Create patios, sitting areas, paths and walkways over 1/3 of the landscaped area, and the final third in medium and low water-use shrub and flowerbeds.
• Trenches, crescents, saucers and swales: for higher water-use plants like garden vegetables, consider the use of shallow trenches or swales, sunken areas or depressions where water can flow to and gather naturally. Trench vegetable gardening is an effective method of conserving water, reducing evaporation and shading the soil. Trenches make it easier to lay a soaker hose for irrigation. For an area with a little decorative flair, make the trench for high water use plants saucer shaped. Or create little saucers around new plantings to hold additional water for the new and limited root zone. Swales are natural lower areas or indentations in the landscape. Crescents are berms staggered on a slope or incline to lessen runoff, erosion or capture water for plants.
• Weed beds frequently. Weeds rob your chosen plants of valuable moisture.

Amend The Soil

Amending the soil is a primary step in water conservation. The addition of both organic and the newer inorganic amendments retain water and nutrients in the root zone in our clay, caliche and sandy Panhandle soils. Plants that have ample nutrients in the root zone and an active, thriving biological soil life require less water and are healthier. This means less irrigating, less often. The drainage capacity of the soil is improved, thus allowing rainwater and irrigating to soak in better, rather than running off. The precipitation received is used, not lost.

The extent of amending depends on whether the beds, or zones, will be composed of high, medium or low water-use plants. The most organic matter is needed for high water-use plants, less organic matter for medium water-use plants, and less for low water-use plants (refer to the section on Soil).

Train Your Plants

Less frequent and longer watering duration promotes a more extensive root development that will enable your plant to go for longer periods of time between watering, including periods of drought. When I first learned about xeriscape gardening, Jim Knopf, from Boulder, Colorado, one of the first landscape architects who specialized in xeriscape landscape and design, said he trains his plants. If you water every day or every other day for 10 or 15 minutes, your plants will expect that treatment. There is no point for them to send down deep roots when water is always there at the top 2 inches. When watering less frequent and deeper, at least an inch at a time, the plants will allow their roots to grow deeper to capture the available soil moisture. A study performed in Weslaco, Texas at the Texas A & M Research and Extension Center from November, 2002 to October 2003 in Hidalgo County supports the recommendation to irrigate deeply and infrequently.

To avoid runoff on sloped turf lawns in clay soil, set the irrigation system for a cycle-and-soak program. Set a runtime schedule of 8 – 15 minutes with an adequate soak period (maximum infiltration rate in clay soil is .13 - .25 inches per hour).

Mulching

Mulch reduces evaporation from the soil. All beds should be mulched. Mulches could be either organic (wood chips, bark chips, cottonseed or cocoa bean hulls, composted cottonseed hulls, pine needles, composted manure, compost from the home compost pile, shredded paper and newspaper, etc) or inorganic (volcanic lava rock, stone, gravel, crushed granite, etc).

Apply a layer 2 – 4 inches thick.

A thin layer of fine compost acts as a mulch on the lawn. Grass clippings from a mulching mower also act as mulch for lawns; mulching mowers do not cause thatch.

Mulch reduces soil evaporation, reduces runoff, moderates soil temperature, aids in root development, reduces soil compaction and slows weed growth. Avoid using plastic sheets as a mulch or weed barrier. Weed barriers and mulch must allow for the soil to “breathe”.

Water Smart Program

Use the Water Smart Program. Many states and local communities have water smart programs – programs for water conservation. Our local Water Smart program is a water-conserving system developed by the City of Amarillo, Utilities Division, in association with the Potter-Randall County Texas Master Gardeners, the Texas Cooperative Extension Service, and the Texas Panhandle Irrigation Association. Copies of the Water Smart handbook, Using Water Efficiently, have been available from the City of Amarillo Water Department. (free brochures about water conservation, go to http://www.twdb.state.tx.us/assistance/conservation/pubs.asp on the Texas Water Development Board website).

Water by the Plant’s Schedule

There is more than one way to determine when to water your plants.

Evapotranspiration Rates

Each plant has specific water requirements, but most plants have not been scientifically tested to determine exact water needs. Agricultural crops and turf grasses have been tested. The amount of water required for optimum growth is referred to as the evapotranspiration rate (ET), or potential evapotranspiration (PET), a combination of evaporation from the plants and transpiration of soil moisture. Factors that contribute to the ET rate are the plant itself, air temperature, solar radiation, humidity, wind speed, and cloud cover. Factors not included in the ET rate are soil texture and composition, including organic content, aspect (slope or lay of the land), maturity of the plant and mulch cover.

Gardens are composed of many different plants. To determine the optimum amount of water, for simplicity’s sake, these plant groups are referred to as low, medium and high water-use. The ET rates for common turf grasses can be used as a general, corresponding ET rate for the plant groups, as follows:

• Low water use plants: Buffalo grass ET rate
• Medium water use plants: Bermuda grass ET rate
• High Water use plants: Bluegrass and Fescue turf grass ET rates. (In some areas, Bluegrass is shown as the highest water user, while fescue is noted as less, although still in the high water-use category.)

Using the ET Rate to Determine Water Needs

Currently, I know of no source for the daily ET rate for our area. The ET rate is represented by a number usually less than one inch, such as .09, .14 or .22, etc. denoting the amount of evaporation and transpiration of water during the previous 24 hours.

To use the ET rate to determine when to water, keep a log of ET rates from the date of your last watering. When this total adds up to an inch or more, it's time to consider watering again. If it rains during this time period, subtract that amount of rainfall and wait until the total is at least 1 inch again.

Buy a good quality, accurate rain gauge. Rainfall amounts are generally reported at the weather monitoring station. Their recorded precipitation, more often than not, will not be the same amount of rainfall you've received. Our rainfall, like our hail, can vary from city block to city block. If you live outside of Amarillo, rainfall for your town, area, or ranch will usually not be reported.

General Watering Recommendation

Many of the plants mentioned in this website are drought tolerant plants. I’ve used the terms drought tolerant, xeric and low water-use interchangeably. Recommendations are based upon my personal experience of gardening in Amarillo combined with water recommendations by various Southwest gardeners and garden writers. Drought tolerant plants with a mulch cover, grown in properly amended soil with adequate soil drainage, during average Amarillo climate conditions, require only an inch of water each month during the growing season.

If more than an inch of precipitation is received during a 30-day period, that amount does not carry over into the next month. That is, if five inches of rain are received in June, in 30 days time, low water-use plants would need supplemental irrigation of 1 inch, provided another 1 inch rainfall had not occurred. Do not skip watering for 5 months. Xeric plants would most likely survive the drought, but they would not perform up to our expectations as beautiful blooming garden specimens. That is why xeriscape principles recommend providing supplemental irrigation – to grow beautiful gardens.

My definition of medium water-use plants calls for 1 inch of rainfall or irrigation every two weeks with high water-use plants requiring one inch of water a week. Again, this water recommendation is based on plants grown in properly amended soil, with a mulch cover during average Amarillo climate conditions. Plants subject to more extreme heat and windy conditions would require more irrigation, whether they are low, medium or high water-use.

Monitor Soil Moisture

Test lawn and bed areas using a soil probe or 6” screwdriver. If the soil probe or screwdriver can easily be inserted in clay or caliche soil, soil moisture is sufficient. If the probe cannot easily be inserted 6 inches, it’s probably time to water.

Monitor new plantings of plants carefully, adjusting their water needs with the severity of the weather. Water the plant for the size of the root zone. When the plant is young, the root zone will be small and more frequent watering will be required. If a plant is purchased in large containers, gallon size and larger, less frequent watering is required than for 2” and quart-sized plants.

Appearance of the Plant

Another method to determine irrigation schedules is by the appearance of the plants. The color of the leaves of Bluegrass and fescue will dull and curl. If footprints remain visible after walking on the lawn, it’s time to water. The leaves of Bermuda grass will turn brittle. Native buffalo grass may turn brittle too, however, it will green up quickly after irrigation or rainfall.

If the plants are droopy and wilted – it’s generally time to water. But not always. Plants in water logged soil exhibit similar symptoms to plants undergoing drought-stress. Avoid frequent watering to alleviate heat stress in plants, they could end up water-logged and dead. Xeric plants have varied mechanisms to reduce evaporation that may mimic wilting or curling. It’s important to know the characteristics of the plants.

When to Irrigate

Roughly 50% of irrigated water is lost to evaporation on sunny, windy summer days using aboveground sprinklers. Water before 10:00 a.m. and after 5 p.m. or later during the middle of the summer.

Avoid above ground watering on windy days, a real trick to do in the Texas Panhandle, where we are blessed with abundant air circulation. Drip irrigation is the best method for efficient use of water.

Monitor plants and soil moisture and spot-water new plants in an established bed, instead of watering an entire bed. This is especially important in filling in areas in low water-use beds. Extra watering to already established low water-use plants is not necessary and could be detrimental to them.

Adjust automatic sprinklers often for rain or change of season. The convenience of automatic sprinklers often leads to water waste and over watering. The Denver Water Office of Water Conservation states that 85% of all landscape problems come from over watering (McClure, A Practical Guide to Using and Conserving Water in the Garden).

If not watering by ET rates or soil moisture, water lawns when footprints are visibly evident after walking across the lawn.

Fall planting of perennials will save on water. As the days advance into cooler weather, less water is required to establish plants. By the time the next spring and summer comes around, their root zone will be greatly increased.

Water Sense

Although it is better to water less frequently and deeply, this should be balanced with what's called evenly moist. Deep watering doesn't mean watering down to a depth of 3 feet or more. Roots of plants in the upper two feet of soil account for over 50% of the plant's water uptake (Robert Kourik, 1992). Lawns should be watered to a depth of 4 – 6 inches (Master Gardener Handbook), or to most of their root zone, if deeper. A plant's uptake of nutrients, using water, is at peak performance when evenly moist. If the soil is too dry, or too wet, nutrient uptake is reduced or stopped in either extreme. For underground and under mulch drip systems, finger-test for soil moisture or use a soil probe to help in determining when irrigation is necessary.

Drought tolerant plants do not like soggy roots, but need the soil to dry between watering. Drought-tolerant plants have better adaption mechanisms to survive long periods of lower soil moisture, just as bog plant have adapted to very wet soil conditions. Many of the plants we choose to grow fall in-between these two areas. Even though you may have low water-use zones, a typical xeriscape landscape will have medium and high water-use zones as well.

Drip systems can be regulated for the separate zones and soil conditions. With the use of an under-mulch or under-ground drip system, it is much easier to maintain evenly moist conditions, at the same time conserving water. The aboveground mulch cover slows evaporation.

Water Catchment Systems

Consider the implementation and use of a water catchment or rainwater harvesting system. Before buying a system, first determine whether the harvested rainwater will be used for drinking or food preparation, or landscape use. Do you need to harvest rainwater for all your water needs, or just to supplement irrigation?

Most catchment systems aim to capture rainwater/snow melt primarily from rooftops. Approximately 600 gallons of rainwater can be harvested with one inch of water over 1000 sq. ft. Catchments could be creatively designed to include cemented areas to direct rainwater from sloping areas into vegetation or to store underground.

Catchment systems have three main components:

• The catchment area: mainly rooftops, driveways or slopes;
• The gathering system: gutters, downspouts, channels, canals, dry river beds and filters;
• The distribution system: spout and watering can, hoses, pipes, pumps, or a tie into an irrigation system.

Rain catchment barrels can be ordered from catalog or Internet garden supply companies. If undecided on the barrel size, choose the larger barrel or tank. Like storage buildings, no matter what the size, the final building or barrel usually ends up to be too small in the long run.

A minimalist water catchment system is setting a five-gallon bucket to capture roof runoff for potted and container plants.

Container Gardening is Water Efficient

• There are some plants or flowers we just don't want to do without. If some of these are high water-use, plant them in containers, if possible, and water frequently.
• For even less water use and lower maintenance, plant drought tolerant plants in containers. Xeric plants that are not cold hardy for our area are an excellent choice for summer container gardening.
• Use water-holding gels and/or organic matter in your container soil mix for increased water retention.
• Larger containers require less frequent watering than small containers, and insulated containers evaporate less water. The lightweight foam containers are ideal and come in many pleasing designs and colors.

Recycling

Recycling gray water can be as simple as saving and using undrunk water from coolers, water glasses, and tea kettles to saving vegetable, pasta and boiled egg water used in cooking, unused pet water, hand-rinse and clothes wash-water using soap, not detergents. Consider installing special plumbing for its total recapture.

• Never use toilet water or waters containing pathogens and harsh cleaners, detergents, solvents, pesticides, or other chemicals.
• Use water immediately without storing and rotate its use in different lawn or landscape areas depending on the water's source.
• Avoid using gray water on edibles for safety.

Large-scale reclamation of gray water may have two drawbacks in your community. The first consideration is a question of water rights. Is your city water required to be sent on downstream after treatment for subsequent water right holders? The second consideration in large-scale gray water recapture is that it must meet sanitary regulations.

Use Surfactants And Water-Holding Gels

More attention is being given to the practice of applying a surfactant before watering for better absorption. Surfactants alter the surface tension of the waters. Instead of running off when it hits, water can work into the soil more freely. Surfactants are wetting agents like dish soap and can be purchased at garden centers. Some organic gardening books include recipes for making surfactants.

Another recent scientific advance is in the area of water-holding gels or water crystals. Water-holding gels are horticultural polymers that can be mixed into the soil. Results have shown they reduce the irrigation needs from 25% to 50%. Water crystals are sold under a number of different names. It can be mixed in the flower bed and container soil. I have used this in my container plantings and find that even during some low 90° weather, I can go 2 days in-between watering my large containers. Often during mild weather in spring or fall, only watering every 3 – 4 days is required, or even a week.

The gels or crystals last for several years before breaking down into "pore-clogging slime" that hinders soil aeration, but ultimately dissolves. Changing out container soil annually and recycling it to the compost pile solves this problem. But be careful if using for low water-use plants, their roots could rot during an extended wet spell. Adding compost/humus to the flower bed or containers is a natural way to improve the water holding capacity of soil.

Angie Hanna