Summers are tough for a desert botanist. It pains my heart to look out across both our yard and the open desert and watch the native plants turning brown, dropping their leaves, and shutting down for the summer. I know that these plants have to do this just to survive the coming months of intense sun, 100+ degree heat, and no promise of rain for most of the year. Yes, the scientist in me knows that all these desert plants have adapted to this climate by taking an obligate summer sleep, designed by nature to slip into dormancy for the summer, and that shutting down is what allows them to survive the brutal summers here. But it hurts me, none the less.

Like watching our friends struggle, it's hard to see desert plants go through long summers with no water.

Like watching our friends struggle, it’s hard to see desert plants go through long summers with no water, resorting to dropping all their leaves and going dormant during extreme conditions.

This is a strategy used by plants from deserts around the world. When the soil is hot and dry, the plants sleep. When the soil is cool and wet, they wake up and grow. I know that I must resist the urge to keep their soil wet over the summer; I would not be doing them any favor to constantly water them, because soils that are wet when they are hot would only grow harmful bacteria and fungus that cause root rot, and deprive the roots of needed oxygen, especially when soils are hot. I would literally kill my native plants with kindness.

But wait–it’s not the water per se that kills desert plant roots in the summer; it’s continuous water in hot soil that kills them. So what if we could occasionally deliver the water down into a soil depth where the soil isn’t hot? Moisture in cool soil doesn’t grow root pathogens like it does in hot soil. An occasional summer thunderstorm can be a natural occurrence in the desert, and that doesn’t hurt the plants, because it is fleeting moisture, soaked up by roots, and quickly drying out; the soil will not be soaked again for many weeks or months. Infrequent soakings don’t create enough incubation time for big populations of harmful soil microbes to grow and cause root rot.

So here is a strategy to help native and other desert-friendly plants get through summer with less pain for them and for their human garden stewards: during the summer, deliver water deep into the soil occasionally with “deep water stakes”, soaking subterranean soils several feet below the surface where soil temperatures are much lower.

Deep-water Stakes

Deep-water stakes are available in 1, 2, and 3-foot lengths to deliver water deep into the ground with no surface evaporation, delivering that water into cooler subterranean soil layers.

We decided to try this method when our 25-year old, 15-foot tall row of sugarbush plants (Rhus ovata) started showing the stress of seven years of severe drought. They have not been on an irrigation system for decades, since they are native to our valley and normally receive adequate moisture from seasonal rains. But seven years of almost no rain was just too much for them. Their leaves turned brownish-black, most with tiny holes like miniature buckshot; whole limbs were dying, and leaves were becoming scarce on the limbs that were surviving. It was grim. These plants had for years formed a thick privacy screen along our property boundary. Now we could see right through the branches.

Deep-water stakes to the rescue! We bought dozens of 2-foot long, hollow plastic watering stakes with holes along the sides, and a pointed end to make installation easy with a rubber mallet or hammer. In some places, our soil was so dry and compacted, we had to soak the soil with water first to pound the stake in.

We installed a stake between each adjacent plant, and one stake on either side of each sugarbush. We were careful to place the stakes under the “dripline” of each plant, the area under the ends of the branches, where the root system is most active and absorbs moisture. The area right next to the crown of the plant, where the stem comes out of the soil, does not have roots that still absorb water; roots near the crown have barked over, providing structure but not absorption. Many plants suffer from fungal rot if the soil near the crown is continually saturated during warm weather.

Sugarbush leaves before and after deep watering

Sugarbush leaves before and after deep watering.

These watering stakes are not cheap, but we weighed the cost of losing our trees, and watering much more frequently at the surface and possibly still losing the trees, versus the water saved by watering deeply only every few months.  We felt the expense was worth it in the long run. You can make your own deep-water sleeves by cutting short sections of PVC drainage pipe, digging holes next to your plant, burying the sleeve under the dripline of the plant, filling it with gravel, placing your irrigation line through one of the holes, and buying a PVC cap to keep dirt and animals out. However, the caps are fairly expensive, and digging the holes to bury the sleeve next to existing plants is very labor-intensive and can damage plant roots. Deep-watering sleeves made of drainage pipe are most practical if they are installed when a new plant is first planted. We also like the ease with which the manufactured stakes can be pulled out by sliding a screwdriver through the top set of holes, pulling the stake out of the ground, and pounding it back in further from the plant’s crown as the plant grows.

Adapting a garden hose to fit into deep water stakes, which are normally designed for 1/4" irrigation tubing. We place a washer over the opening of the stake when the cap is off to keep dirt out of the stake.

Adapting a garden hose to fit into deep water stakes, which are normally designed for 1/4″ irrigation tubing. We place a washer over the opening of the stake whenever the cap is off to keep dirt out of the stake.

The cap of each stake has a small slit to allow placement of a ¼-inch irrigation line into the stake before fitting the cap over the stake. Since we don’t have irrigation to this far section of our yard, we rigged up a hose ending that fits down into the stake (plastic tubing attached with a hose adapter to a garden hose), and watered with our garden hose.

To reduce the end size of your garden hose to fit down into narrow deep-water stakes, buy a screw-on hose adapter to fit onto a short piece of flexible plastic hose.

To reduce the end size of your garden hose to fit down into narrow deep-water stakes, buy a screw-on, plastic hose adapter to fit onto a short piece of flexible plastic hose.

We slipped our plastic tubing into the stake, turned on the faucet to a fast drip/slow drizzle, and set a timer for 6 hours per stake. To our amazement, we started to see not just new leaves, but entire new branches growing within two weeks. We did this just once in April, and again in June. We will not water them again until August or September, if we don’t get any monsoonal rains. With ample winter rains, supplemental irrigation won’t be necessary; however, if we have just a small fraction of our normal winter precipitation, as we have had for multiple years in the past, we might try one deep-watering session over the winter. If these plants hadn’t been so stressed from years of drought, they could likely thrive with just one or two deep watering sessions per year. So many new branches have regrown on every plant that we again have a thick privacy screen shielding us from the street. We feel we rescued these beauties from possible death, or at least a fate so unsightly we would have had to cut them back severely and hope for some regrowth next winter.

We will be testing deep-water stakes on some of our other deep-rooted native plants to determine whether an occasional deep, subterranean soaking keeps them from going totally summer dormant. Like they say, we don’t want to fool Mother Nature, but we would like to give our valiant desert native plants a little boost during our new climate regime of hotter and drier days. We will report back on our results.

Until then, remember that occasional deep soakings are better for your desert-adapted plants than frequent, shallow watering. Deep watering teaches plant roots to grow down deep to find moist soils, protecting roots from drying out at the surface.

Sugarbush after deep watering_4752

Privacy screen of mature sugarbushes with new flush of leaves and branches after being watered with deep-water stakes following a seven-year drought that killed off most of the branches and leaves.

Shallow watering teaches roots to stay near the surface to find moisture, but surface soils heat up fast and dry out quickly. There is little protection for shallow roots if the surface soil heats up and dries out. Roots will never learn to go deep if trained to stay shallow—condemning both of you to a schedule of constant irrigation. For desert native plants, frequent summer watering can speed them toward root rot and death. If you can’t resist watering your struggling natives during the summer, make like a summer thunderstorm and put lots of water on them over one or two days, then let the soil dry out completely before creating another “monsoonal storm”.

As we sip wine on our Hobbit Deck at sunset, it make us smile to look over our 1/2-acre desert garden and see native plants not just surviving this extreme summer heat, but thriving.

 

P.S. Deep-water stakes are available locally at Cactus Mart in Morongo Valley, Home Depot stores, and online from “Deep Drip Watering Stakes” at www.deepdrip.com.

 

Deep Drip Stakes_Trees

Placement of 24-inch stakes for trees. Courtesy deepdrip.com

 

Deep Drip Stakes_Shrubs

Placement of 14-inch stakes for trees. Courtesy deepdrip.com

 

May
1
0

Plant of the Month – May

Large, eye-catching flowers adorn this carefree shrub that performs impressively in extreme conditions with almost no maintenance, taking drought, poor soil, wind, and heat in stride.

Bicolor Rock Rose

Cistus x cyprius var. ellipticus f. bicolor
  • Plant Form: Evergreen shrub
  • Water Use: Low
  • Mature Size: 3-4 ft. tall x 4-7 ft. wide
  • Exposure: Full Sun, Part Sun
  • Bloom Time: Late Spring (April-May), Summer (June – August)
  • Native to: Mediterranean region
  • Hardiness: Cold hardy to 15°F

Bicolor Rock Rose looks so elegant in bloom that it may fool you with its sturdy, easy-care nature. This rock rose tolerates drought, poor soil, drying winds, and desert heat. Clusters of large, white, crepe-like flowers with golden “eyes” and five burgundy spots cover this evergreen shrub from late spring to summer. Although each flower lasts only one day, buds are so abundant that bushes produce an endless procession of color for two or three months. This low-maintenance plant is best pruned in late winter after threat of frost has passed. Its growth habit of being both upright and widely sprawling make it ideal for use on dry slopes as a groundcover, as well as for borders and low hedges. Charming in both Mediterranean-style gardens and cottage gardens. Adds evergreen beauty to rock gardens, and performs great in containers.

Check out our  “Garden Tasks” for May

Golden Barrel Cactus
Echinocactus grusonii

Everything about this plant makes it a desert gardener’s delight: extreme drought-tolerance, very low maintenance, suitability for both formal and casual landscapes, attractive clumping habit, and glowing spines for added interest.

  • Plant Form: Cactus/succulent
  • Water Use: Very Low
  • Mature Size: 1.5 ft. tall & 2 ft. wide (3 ft. tall and wide in very old plants)
  • Exposure: Full Sun, Part Sun
  • Bloom Time: Spring (Mar-May), Summer (June – August)
  • Native to: Central Mexico
  • Hardiness: Cold hardy to 18°F

Golden Barrel Cactus is one of the most popular cacti in cultivation today—one look, and you’ll know why. Bright golden spines line the ribs of this spherical cactus, which lights up in the sun. Older specimens produce offsets around their base, eventually forming large clusters with dozens of individual heads. Yellow flowers form late spring to summer in a ring at the top of the plant on larger, mature plants only, peeking out of the dense patch of white woolly hair that protects the top of the barrel. Planted in mass, these whimsical plants create a dramatic effect, even giving the illusion of rolling hills in a flat landscape. Golden Barrels keep getting more beautiful as they grow, needing very little care or water, and usually only suffer if they get not enough sun or too much irrigation. Plant groups close together among large rocks for impact. Wonderful in containers on sunny porches and in atriums.

 

Check out our  “Garden Tasks” for April

Spanish Lavender
Lavandula stoechas

Spanish Lavender offers a trio of qualities that gardeners seek: beautiful blossoms, drought tolerance, and fragrant foliage. Add to that rabbit resistance and tolerant of heat, cold, and poor soils, and you have a real winner!

  • Plant Form: Evergreen perennial
  • Water Use: Low
  • Mature Size: 24 – 30 in. tall & wide
  • Exposure: Full Sun
  • Bloom Time: Spring (Feb-May), Summer (June – August)
  • Native to: Mediterranean region and North Africa
  • Hardiness: Cold hardy to 15°F

Spanish Lavender can fulfill your desire for a durable evergreen plant with bright flowers, enchanting fragrance, drought resistance, and heat tolerance. Both flowers and foliage are wonderfully fragrant. Purple bracts on flower heads appear like rabbit ears, and lend a whimsical look. Spanish Lavender is probably the same plant that the ancient Greeks and Romans used to scent their bath water, and is still popular today for dried aromatics and cut stems in homes. Prune lightly after flowering to stimulate next season’s growth. This water-wise, easy-care plant is perfect in both formal and casual Mediterranean-style gardens, as well as in cottage and wild gardens. It also performs superbly on dry slopes and rocky outcrops. Spanish Lavender attracts butterflies and pollinators, but luckily repels rabbits. Beautiful in large artistic pots, mixed borders, mass plantings, and rock gardens.

Check out our  “Garden Tasks” for March

Trailing Indigo Bush
Dalea greggii

Trailing Indigo Bush is one of the toughest groundcovers available, resisting drought, heat, and rabbits, while offering soil stabilization on slopes and a durable cover in rock gardens and medians.

  • Plant Form: Evergreen groundcover
  • Water Use: Low
  • Mature Size: 1-2 ft. tall & 3-9 ft. wide
  • Exposure: Full Sun
  • Bloom Time: Spring (Feb-May), Summer (June – August)
  • Native to: New Mexico, Texas, Mexico
  • Hardiness: Cold hardy to 10°F

Trailing Indigo Bush creates a mounding, low-maintenance, easily established groundcover for any arid location. Silvery blue-green foliage adorns this spreading plant that roots at the nodes of long, trailing stems, covering everything in its path and making it especially useful to stabilize slopes. Its tiny, purple, pea-like flowers are not showy from a distance, but butterflies, native pollinators, and humans appreciate their beauty close-up. This durable groundcover shuns fertilizer and overwatering, but some watering in summer helps keep the foliage full. In the late winter or early spring, cut off the stems of last season’s growth to stimulate new growth in spring. Besides being tolerant of drought and reflected sun, Trailing Indigo Bush is happily rabbit resistant. One of the toughest groundcovers available, it is valued on slopes, medians, in rock gardens, and wherever soil stabilization is needed.

Check out our  “Garden Tasks” for February

Queen Victoria Agave
Agave victoriae-reginae

Queen Victoria Agave_plant_RK

For a stunning accent almost anywhere in your yard, rock garden, on your porch, or in an atrium, it’s hard to beat the elegant form and color of Queen Victoria Agave.

  • Plant Form: Evergreen succulent
  • Water Use: Low
  • Mature Size: 18 inches tall and wide
  • Exposure: Full Sun
  • Bloom Time: Summer (June – August) Blooms once after about 10-15 years in the garden
  • Native to: Mexico
  • Hardiness: Cold hardy to 10°F

Queen Victoria Agave is among the most striking century plant species in cultivation, and looks so perfect, you’ll wonder if it’s real. Each thick leaf of the symmetrical rosette is edged with precise white lines wherever the leaves are angled. A single spine finishes the tip of each leaf. Queen Victoria Agave is prized not only for its mesmerizing leaf patterns, but also for its small size and ability to withstand desert heat, drought, and cold. This slow-growing agave may bloom once at considerable age, producing a single 15-foot stalk with reddish-purple flowers, after which the mother plant dies–but not before starting new “pups” from below the rosette. Looks best when watered deeply twice a month in summer and once a month in spring and fall. Like most agaves, this beauty looks great in containers, especially on either side of an entry to view up close. In the ground, it is stunning in rock, cactus, and succulent gardens.

Check out our  “Garden Tasks” for January