Gardening in the Desert – The key is managing evaporation!

By John Zarola, with Dudley Vines

Evaporation occurs due to intense sunshine, high winds, low humidity, and high temperatures—all of which we have in abundance. Methods we can employ to minimize evaporation include

  • Amending the soil with compost to improve water retention;
  • Avoiding bare soil by mulching, shading, and cover cropping
  • Putting the right plant in the right place
  • Incorporating efficient irrigation options

AMENDING THE SOIL
Compost is decomposed organic material. Amending soil with compost improves
water infiltration and retention. Because compost decomposes (adding nutrients to the soil), it should be replenished every Spring and Fall. Compost can be used as a topical application or mixed into the soil.

MULCHING & SHADING
Garden Mulches are protective soil covers of various materials placed around
plants. Mulch reduces evaporation and overall water use, moderates soil temperature fluctuations, reduces weed growth, softens the effect of rainfall and
protects from wind, reduces soil erosion and compaction, and gives finish and
style to a garden. In addition, organic mulches decompose, improving soil
fertility. When mulching, leave a 4” – 6” gap from base of the plant. And, importantly, irrigation water should reach the soil under any type of mulch.
Water is most efficiently applied directly to the soil.

THE RIGHT PLANT IN THE RIGHT PLACE
What are the “right plants”? To get the most from the water you use, plant
abundant producers like tomatoes, squash, peppers, and egg plant. Plant
drought tolerant vegetables such as black-eye peas, mustard greens,
pole/snap beans, New Zealand spinach, chili peppers, garbanzo bean, tepary
bean, amaranth, chard, and some varieties of tomatoes. Plant only what you
can reasonably care for in the time you have available. Landscape with low water use plants suitable for our climate zone. Plant perennials(trees and shrubs) in the Fall – less heat means less stress on the plant while the root system is being established.

What about the right place? Here are some things to think about:

  • Group plants with similar water requirements together
  • Consider prevailing winds
  • Consider microclimates – masonry walls
  • Consider the use of movable pots and planters
  • North side: Winter cold; Summer heat
  • South side: midday and afternoon sun
  • East side: morning to midday sun
  • West side: intense afternoon heat in summer
  • Provide shade using row covers, structures, arbors, lattice, companion
    planting, or dense planting

EFFICIENT IRRIGATION
Water management options include rainwater harvesting, clay pot irrigation
(ollas), self watering planters (pots), jug drip technique, drip irrigation, soaker
hose, and recycling household gray water. Water early in the morning (before
sunrise) to prevent evaporation, water infrequently but slowly and deeply, and
water at the dripline, where the absorptive roots of the plant are.

Lastly, too much water wastes money, and too little can kill the plant. How do
you know if you’re watering correctly? You can check the soil moisture by feel,
and you should most definitely watch your plants for evidence of irrigation problems.

Signs of Underwatering

  • Soil is bone dry
  • Older leaves turn yellow or brown and drop off
  • Leaves are wilted
  • Leaves curl and become brittle
  • Stunted growth
  • Plant is dead

Signs of Overwatering

  • Soil is constantly saturated
  • Leaves turn a lighter shade of green, or turn yellow
  • Young shoots are wilted
  • Leaves are green yet brittle
  • Algae and mushrooms are present
  • Excessive growth
  • Plant is dead