#135 Summer Stress in the Desert

The Causes and Solutions

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By understanding these common causes of summer stress and implementing the preventative measures outlined, desert gardeners can ensure their plants thrive throughout the hot season.

Desert climates pose unique challenges for plant life. Extreme temperatures, low humidity, strong winds, and poor soil quality can take a toll on even the most resilient flora. This guide explores the four main causes of summer plant stress and offers solutions to keep your desert garden flourishing.


A Word of Caution: Avoid pruning sunburned foliage during summer. These damaged leaves provide temporary protection for the rest of the plant. Prune them only when cooler weather arrives.

CAUSE #1: IMPROPER PLANT SELECTION

When selecting plants for your desert garden, consider the sunlight conditions where you plan to place them. Some plants thrive in full sun, including reflected sunlight. Others, however, prefer partial shade or even full shade. Keep in mind that many flowering plants, especially fruit trees, require significant direct sunlight to produce blooms and fruit (since flowers are necessary for fruit production).

Grower instructions: The “plant care instructions” provided by growers often cater to specific regional climates. For example, instructions for a plant grown in California might be tailored for a “California climate.” These might not be ideal for the unique challenges of the Desert Southwest.

Look for Our Plant Signage

We provide signage for each plant to help you choose the best location. Here’s how to interpret the information:

“Prefers Afternoon Shade”: This plant needs shade in the hottest part of the day, typically the afternoon. Ensure the chosen location receives shade during this time and avoid reflected sunlight.

“Full Sun”: This plant thrives in direct sunlight for most of the day. However, it might tolerate some shade without significant issues.

When in Doubt, Ask Our Experts

If you’re unsure about a plant’s light requirements or its suitability for your chosen location, don’t hesitate to ask! Our trained nursery advisors are happy to assist you in making the right choice for your desert oasis.

CAUSE #2: IMPROPER PLANT LOCATION 

Symptoms: Burned leaves, typically concentrated in one area; discolored or cracked bark, often accompanied by sap oozing; sunken, papery leaves; recurring lanky, soft growth that withers and dies.

Causes: Placing the wrong plant in the wrong location. Many plants are sensitive to desert sun exposure. Sun-loving plants can burn if positioned near a reflective surface like a light-colored wall, reflective glass facing south or west, or extensive areas of paving or rocks. Be mindful of the reflected sun from your pool as well. Fruit trees, young deciduous trees, and some willow species are susceptible to trunk sunburn, typically on the southwest side. Sunburned areas expose the cambium attracting ants, green beetles, and borers. Conversely, sun-loving plants may struggle in excessive shade, resulting in weak, droopy, pale growth that may eventually die.

Solutions:

  1. Mulching: Apply a good-quality, fully composted mulch like Dr Q’s PAYDIRT® around the plant base. A 1-2 inch layer will help retain moisture and cool the roots. Consider using bark or mulch in a “ring” around plants surrounded by rocks, as rock heat reflection significantly contributes to stress. Refer to Star Note #620, “Mulching for Healthier Plants,” for further details.
  2. Plant Relocation: While relocating a stressed plant during summer heat might not be ideal, it’s an option. For non-frost-sensitive plants, consider transplanting in October. For frost-tender plants, wait until the following March, just after the last frost. However, for immediate relief:
    • Provide temporary shade: Use shade cloth to drape over the plant, allowing sufficient sunlight while protecting it from scorching. Avoid using burlap during summer.
    • Protect sun-sensitive tree trunks: Apply diluted white latex or tree paint to clean, debris-free sunburned trunks. Many plants develop increased sun tolerance as they mature and establish larger canopies to protect themselves. Providing extra care while they’re young is beneficial.

CAUSE #3: IMPROPER WATERING

Symptoms:
Wilting, scorched leaves with brown edges, new leaves yellowish or off-white with green veins, sudden plant death with a freeze-dried appearance.

Often, improper irrigation practices and emitter placement contribute to plant stress. Frequent, short watering sessions are common, but this encourages shallow root systems that struggle during hot spells. Over-watering and under-watering present similar symptoms. Under-watering leads to the plant dying due to water deficiency. Over-watering forces air out of the soil, suffocating the roots and preventing adequate water uptake, ultimately causing plants to die. In desert climates, over-watering is a leading cause of plant death. Most desert soils are heavy alkaline clays with layers of calcium carbonate (caliche) and poor drainage. Excessive watering creates “bathtubs” filled with salty water. High alkalinity, exacerbated by frequent watering, hinders nutrient absorption despite supplementation. This commonly results in being misdiagnosed as iron deficiency “chlorosis”. Plants forced to utilize salty, alkaline water expel salts as far as possible from their roots, causing leaf tips to burn and turn brown and crispy, with salts sometimes visible on the leaf surface.

Over-watering a lawn or watering in the evening is likely to cause a fungus. This disease will leave your lawn with brown spots, potentially causing you to believe it needs even more water.

WATERING WISELY IN THE DESERT

Watering Wisely:

  • Trees & Shrubs: Deep Soaking for Healthy Roots

Deep watering is crucial, especially for desert soils like clay or caliche. Unlike short bursts, running drip systems or bubblers for several hours, depending on the size of plants, encourages deep root growth. This has two key benefits:

  • Stronger Roots: Deeper roots access more moisture stored in the soil, making your plants more resilient during dry spells.
  • Salt Displacement: Deep watering helps push away accumulated salts that can harm your plants.

Remember, “infrequent” watering doesn’t mean daily. Adjust the frequency based on your soil type, the specific plants you have, and the current temperature. Star Notes #900A and #905 offer more details on watering schedules.

  • Lawns: Lawns generally require more frequent watering due to their shallow root systems. If your lawn has brown patches and appears unhealthy, ensure your sprinkler system functions correctly and water at the right time of day (avoid 9 PM to 2 AM). Refer to Star Note #900B for more information. If your trees and shrubs are on the same irrigation cycle as your lawn, separate them. Our irrigation consultants can help you.
  • Drainage Matters: Lucky enough to have well-draining soil? You might need more frequent watering for both shrubs and lawns. Use a moisture meter to gauge water needs.
  • Bubbler Efficiency: For bubbler systems exceeding 10 gallons per hour (gph), run for at least 10-15 minutes to ensure proper coverage for shrubs.
  • Mulch Magic: A layer of mulch works wonders by conserving moisture, cooling the soil, and enriching it for both shrubs and lawns. If you notice salt buildup (white crust), flush the area twice a year with an acidic product like Con-Gro to improve drainage.

FERTILIZING FOR SUMMER SUCCESS
High-nitrogen fertilizers during summer can stress plants by promoting excessive growth. Opt for a low-nitrogen option like Dr. Q’s Rose Food which provides essential nutrients for roots (5% nitrogen), flowering (phosphorus), and heat tolerance
(potassium).

Signs of Trouble:

  • Over-fertilization: Blackened leaves, excessive leaf drop, unhealthy appearance (even with proper watering). Overly lush growth can also occur, leading to wind damage and increased pest/fungus problems.
  • Under-fertilization: General yellowing, especially on older leaves, stunted growth, weak appearance, and little to no fruit/vegetable yield.

The Right Approach:

  • Less is More: It’s easy to over-fertilize, especially in hot weather. On the other hand, plants that are undernourished are unhealthy looking and prone to other summer ills like windburn and chlorosis Choose the right fertilizer for your plant and season, following package directions carefully. When unsure, use less – you can always add more later.
  • Potential Damage: Over-fertilization can be addressed by flooding the plant with water twice, a week apart, to remove excess fertilizer from the root zone.
  • Temperature Matters: Pay attention to fertilizer application timing based on seasonal temperatures. Some release nutrients faster in hot weather, potentially harming plants, while others may not release them at all in cold weather. Refer to Star Note #600 for fertilizer type details.

ADDRESSING SUMMER WIND AND PESTS:

  • Wind Damage: Avoid planting brittle trees in high-wind areas. Ensure proper staking for young trees to prevent breakage or bark damage. When hot, dry winds blow, plants use more water. Extra watering might help, especially for broad-leaved and newly planted specimens.
  • Desert Pests: Fungi and insects can and do attack in hot weather. Proper diagnosis is crucial for an effective cure. Our certified advisors can help identify the problem and recommend appropriate insecticides or fungicides.

PREVENTING SUMMER STRESS IN THE FUTURE:

  • Know Your Plants: Research the specific needs and tolerances of your chosen plants. Don’t rely solely on grower labels.
  • Spring Irrigation Checkup: Each spring, inspect your irrigation system for leaks or malfunctions. Refer to Star Note #910 “Irrigation Tune Up” for guidance.
  • Deep Root Encouragement: Help expand your plant’s root systems by adding drip emitters further away from the plant’s base, to extend beyond the plant’s drip line.
  • The Power of Mulch: Maintain a consistent layer of mulch around your plants.
  • Consult the Experts: Our Star Nursery Advisors are available to answer any questions you may have.

By following these tips and consulting with our experts, you can ensure your desert garden thrives throughout the harsh summer season. Remember, healthy plants are better equipped to withstand the challenges of a desert summer.

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