Drought-tolerant landscapes

By Katie Navarra

Water is the lifeblood of every living species, and drought areas are increasing. According to the Environmental Protection Agency (EPA), a government report found that water managers in 36 states expected to face water shortages in 2013.

Well planned landscapes that incorporate drought-tolerant elements provide landscape professionals and property owners the opportunity to increase the likelihood of a landscape’s survivability during a drought while potentially reducing the overall water usage within the landscape.

Drought-tolerant landscapes provide additional benefits, including enhanced curb appeal and potentially lower maintenance costs.

“(Drought-tolerant) landscapes incorporate more interesting plant species and that variety can be colorful and vibrant and increase a home’s value,” said Amber Lefstead, outdoor coordinator for EPA’s WaterSense Program.

Carefully planned, drought-tolerant landscapes also have the ability to save property owners on maintenance fees. “Especially native plants will require less fertilizer, less time because they are adapted to the climate and conditions of the landscape,” Lefstead added.

What is a drought-tolerant landscape?

A drought-tolerant landscape is a landscape that uses species of plants proven to be resilient during continuous periods of months or years when a region receives less-than-average rainfall. Drought-tolerant landscapes may also incorporate elements such as pavement, walls, or overhead structures to reduce intense sun, radiated heat or cracking earth.

Understanding the natural climate of the region is critical. “If the natural weather cycle includes, for instance, a hot, dry summer (which is usually associated with a cool, wet winter such as in Mediterranean climate), then plants must be selected that are either indigenous to or tolerant of that climate,” said Danilo Maffei, Association of Professional Landscape Designers (APLD).

Selecting plant material that is indigenous to the area can be considered an “insurance policy” so that, in the event of an extended drought, the majority of the landscape survives the event, said Maffei.

There is a misconception that drought-tolerant landscapes are laden with rocks and cacti, limiting a homeowner or commercial property owner’s options for incorporating diversity. “That is not necessarily true, unless living in very, very arid, areas,” said Lefstead.

It is also important not to confuse a drought-tolerant landscape with a xeric garden (also known as xeriscaping). Although the practice of design in either case is similar, there are key differences where the designer seeks to create a product that meets criteria for usability, durability, aesthetics and enjoyment.

“A drought is an occasional phenomenon, so plants are selected for a drought-tolerant landscape that essentially ‘hedges your bets’ in the garden,” said Maffei. “A water-efficient landscape is designed under the premise that there will never be ample moisture, as in it is a xeric garden, or it is impractical or forbidden to use supplemental irrigation.”

Drought-tolerant landscapes require planning

“Plant choice determines water use,” said Lefstead. Native, regionally specific plants require less water to survive in their natural environment than plants forced into geographic areas fore which they were not originally designed.

Choose the right plant for the right place. Sun-loving plants should be planted in the sun, and shade loving plants should be planted in the shade. “Take time to understand the site and lighting,” said Lefstead. Plants placed outside their natural “comfort zone” will struggle and need more water to look healthy.

“Group plants together based on the amount of water needed,” Lefstead said. Hydrozoning includes grouping plants with similar water needs in the same beds to more efficiently provide water based on plant needs. In areas where plants are not grouped, too much water is applied to ensure the plants needing more water get enough and vice versa, she added.

A drought-tolerant landscape design also strives to minimize steep slopes. In situations where steep slopes are unavoidable, plants with deeper root zones, native ground covers and shrubs provide additional stabilization to avoid runoff and erosion.

Turfgrass used in drought-tolerant designs is placed strategically and reserved for areas only where it is practical, such as play areas. The EPA estimates that the typical suburban lawn consumes 10,000 gallons of water above and beyond rainwater each year.

“Carpeting with turfgrass cans use a high percentage of water in the landscape because some people tend to over irrigate,” said Lefstead. Higher mowing heights, especially in summer months, reduce the amount of “thirsty new growth” and longer grass blades encourage deeper root growth. Longer blades provide shade for each other, reducing evaporation and controlling weed growth.

Soil conditions — especially extreme soil conditions of sand, heavy clay or heavily compacted areas — impact a landscape’s ability to be drought resistant. Aeration of compacted areas will increase water infiltration and reduce the need to continually water the plants or grass in the specific area.

“Incorporate mulch,” said Lefstead. “We advise to place mulch around garden plants and shrubs to lessen evaporation. Replace mulch, especially organic materials at least on an annual basis because they degrade.”

Assessing a site’s soil conditions takes time. “Go out and do a soil test,” said Lefstead. Even though it is time consuming to observe the site, it will affect the survivability and water efficiency of the landscape. Local cooperative extensions can provide soil test kits and input on how to improve soil health.

Challenges of incorporating drought-tolerant landscapes

“Right now, it is a little difficult to find native plants compared to ornamentals,” said Lefstead. However, working with local horticulturists can assist in identifying plants that are native to your specific geographic area. Local cooperative extension services have resources available and the EPA’s website (epa.gov/watersense/outdoors/what_to_plant.html) also includes resources on plant selection.

“While some plants may be drought tolerant, this does not mean they are all completely immune to the effects of drought,” said Maffei. “A level of expectation for survivability must be established.”

Drought-tolerant landscapes require care during the establishment period, which can be two or three growing seasons or longer for some plants in some parts of the United States. “These plants are only capable of surviving drought once they have developed a mature root system, so proper supplemental irrigation and cultural care must be administered during that process of growth,” said Maffei.

Katie Navarra is a landscape industry professional based in New York. She is also an accomplished author and freelance correspondent with more than 200 articles to her credit. She can be reached via e-mail at katienavarra@yahoo.com.

Photo above: This landscape in California uses drought-tolerant plants to reduce watering, and mulch to cover the soil, retaining moisture for plant roots and reducing evaporation. Plants are grouped by hydrozone to save water and shade trees increase passive cooling of the landscape, reducing evaporation. All hardscape is permeable, allowing stormwater to stay onsite, and an efficient irrigation system with multi-stream rotator spray heads and drip irrigation reduces water waste.

Photo by Julie Orr Design

Additional resources:

• What To Plant (EPA): http://epa.gov/watersense/outdoor/what_to_plant.html
• Landscaping Tips (EPA): http://epa.gov/watersense/outdoor/landscaping_tips.html
• Association of Professional Landscape Designers: www.apld.org
• American Society of Landscape Architects: www.asla.org