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desert gardening basics
trees, water and xeriscapes
Trees, Water and Xeriscapes
October, 2012, Page 59
Photos by Art Holeman
A native ironwood tree protects a secluded front yard nook, where hummingbirds are drawn to the many varieties of aloe and penstemon that are in bloom from winter to spring.
ACCOMPLISHED PLANTSWOMAN CAROL STUTTARD EXPLAINS HOW TO CREATE A COLORFUL WATERWISE LANDSCAPE
People may look at all the plants in my xeriscape and think it’s a lot of work, but it’s not,” says Carol Stuttard, a transplanted Englishwoman who has embraced desert gardening. “Once established, my plants take care of themselves.”
“Zeroscape,” a pejorative term that sometimes is substituted for “xeriscape,” is a misnomer, Stuttard believes. “Any xeriscape, which I prefer to call water-wise, can be lush and beautiful if you select and site plants appropriately, with varied options offering blooms or seasonal interest throughout the year.”
“Trees are the backbone of any landscape,” says the Scottsdale resident, who learned the ins and outs of desert plants and arid gardening by enrolling in the volunteer Master Gardener course through the University of Arizona Maricopa County Cooperative Extension. She also completed the Desert Landscaper School certification offered at Desert Botanical Garden in Phoenix and is current president of the Scottsdale Community Garden Club. “It’s essential to know the maximum size of the species you are going to plant and allow it sufficient space in your landscape to reach maturity without unnecessary pruning,” she counsels. She says that two common mistakes are transplanting mesquite trees within 10 feet of each other (given their 30-40 foot canopies) and siting a mesquite tree immediately adjacent to a house foundation.
You can determine the mature size of trees from books on plants, other references or nursery tags, although Stuttard also suggests visiting public gardens to see mature plants in landscape settings. “It helps to visualize how tall and wide tree canopies can expand and how they best fit into your site.”
A potted agave flourishes in the filtered light.
October is the premier gardening month in the low desert. “Planting in fall gives plants a much better chance of survival than spring because roots have six or seven months to grow without the stress of intense heat,” notes Stuttard. Spring planting, on the other hand, requires more careful monitoring and frequent irrigation to maintain soil moisture as temperatures heat up. You can save significantly on your water bill by transplanting in fall, especially if you install a large number of plants, she says.
Efficient Water Use
After desert tree root systems are well-established, Stuttard takes the trees off automatic irrigation. In her landscape, native ironwood, mesquite and palo verde transplanted from 24-inch boxes and 30-gallon pots were on irrigation for about five years. Smaller transplants may require more time. “A lot of water is wasted by continuing irrigation on plants that don’t need it, and often the irrigation timer was either not set properly in the first place or has never been adjusted as the plants grew,” she says. “So the system isn’t supplying sufficient water for trees.”
As a Master Gardener volunteer, Stuttard has counseled many homeowners who believed it was sufficient to run their drip systems for an hour on trees daily, using 1-gallon emitters. “I ask them to imagine pouring a gallon jug of water around a mature tree. Is that sufficient water to soak 3 feet deep to moisten the entire root system and spread evenly around the entire canopy?”
Simple rainwater-harvesting methods can help conserve water in the landscape and provide trees with periodic deep soakings that help establish roots. Stuttard creates swales—slight depressions or sunken areas—around planting areas and directs rain that pours off the roof to fill them. “Thousands of gallons of water can be collected from the average rooftop during summer storms,” she says.
Also, wherever possible, use permeable soil surfaces that allow rain to soak into the ground and be stored for nearby roots to absorb, Stuttard advises. Permeable surfaces include mulches (bark chips, compost, decomposed granite), as well as gravel driveways and sidewalks or patio pavers placed in sand without grout. If you are adding new concrete or other impermeable hardscape surfaces, they can be slanted to direct runoff to planting areas rather than into a street.
Photos - Clock-wise from top left: Rock-lined pathways and planting beds define Carol Stuttard’s landscape. • The homeowner (pictured) expands her plant collection inexpensively. She allows a wide variety of low-water-use plants to self-sow, such as chuparosa, emu, lavender, penstemon and rosemary, as well as palo verde and sweet acacia trees. Agave and aloe spread prolifically by producing offsets. • Perennials, cacti and succulents shaded by nearby trees enliven the front walk. • Going vertical with vines cools the home and reduces energy use. Vines also provide greenery and color in narrow planting spaces.
Microclimates are pockets of climate variation within a larger area. In summer, tree canopies form microclimates that filter light, protecting plants from direct sun. In winter, tree limbs act as frost cloth, trapping heat below the branches.
The ground beneath tree canopies creates an ideal microclimate for numerous cacti, succulents, perennials, wildflowers and small shrubby plants that thrive in the dappled light. “Desert gardeners can create a carpet of intertwining plants in this protected environment,” states Stuttard. “Massed plantings provide shade and cool the soil for their neighbors. Compare that to a lone plant struggling to survive in the midst of a sea of gravel, baking in full sun.”
In Stuttard’s experience, many people request “litter-free” trees. Although all trees drop leaves, flowers or seedpods, she believes that’s a small price to pay for the shade they provide for outdoor living spaces and the microclimates they create for other plants. “Don’t worry about raking up this plant material,” advises Stuttard. It serves as free mulch, conserving soil moisture, moderating soil temperatures and adding nutrients as it decomposes.
“Regardless of your skill and experience as a gardener, not all plants will survive,” she points out. Desert conditions are harsh, and perennials and small shrubs in particular do not live as long as they do in other regions. “Gardens are a living, fluid entity,” Stuttard remarks. “Accept that some plants may get too big, they fall over, they die. Just embrace it as an opportunity to redesign or try something else.”
The homeowner grows dozens of varieties of aloe and agave for the structure and form they bring to her garden.
Anchored by a fragrant sweet acacia tree, diverse courtyard blooms include (background to foreground) coral fountain, Mexican honeysuckle, purple heart and the tall scarlet stalk of “mother of thousands,” so called because it produces numerous offspring.
Purple and lime-green allium garden ornaments provide a vivid pop of color among orange aloe blooms.
Money for Grass
Carol Stuttard started her landscape redesign by removing existing Bermuda grass. “Growing grass is like tending a crop, with regular watering, fertilizing and mowing that consumes time, money and fossil fuel energy,” she states. “If the only purpose is to have something green to look at, there are better plant options that don’t require as many resources.”
Stuttard received a rebate from the city of Scottsdale for replacing high-water-use turf with low-water-use plants. Details of the program can be found at scottsdaleaz.gov/water/conservation/rebates/rebturfres. Other Valley cities offer varied rebate programs to reduce landscape water use.
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