Preparing for an Arizona Winter

Frost season in Phoenix typically runs mid-November through February. The frequency and intensity of frost varies in both rural and metro areas for a number of reasons including elevation and population density. Our cooler weather provides us with the opportunity to conserve one of the desert’s most precious resources; water.

Water Savings

From roughly Thanksgiving to the end of February, most desert and desert adapted plants do not require water. You can choose to reduce your watering schedule to just a day or two a week or even turn the controller off completely! If you choose to turn your controller off completely, it’s important to continually monitor your lawn for signs of stress and provide water when necessary  Once night time temperatures return to the upper 70s, you will want to start watering again. Since most plants go dormant during this time of year and you can find the emitter a little easier than when plants are blooming, late winter/early spring is an excellent time to check your irrigation system for any faults or malfunctions. Turn your controller on one zone at a time and verify that each irrigation head is functioning properly.

Protect your Backflow

When temperatures dip below 32 degrees Fahrenheit  your backflow is at risk for damage from freezing water that sits in the unit. Usually, the easiest way to protect your backflow preventer is to cover it with a towel or blanket, as pictured, on the nights that temperatures are projected to drop below freezing.  You can also choose to drain the water from your backflow if you are concerned about prolonged freezing temperatures or plan to be gone for several nights. For more information on how to winterize your home sprinkler system including your backflow, please visit the Colorado State University Extension website.

Frost Protection for your Plants

Cover plants susceptible to frost-damage with cloth towels, blankets, sheets or paper/cardboard boxes to insulate them. Plastic is not recommended for plant cover. Drape the paper or cloth all the way to the ground to help trap heat radiating from the ground under the cover. A nursery can help you identify material made specifically for covering plants. Remove the cover after sunrise each morning or when the temperature reaches 35 degrees.

Plants not native to the Southwest are most at risk for frost damage. These plants include Bougainvillea, Lantana, Winter Annuals and others. For cacti such as Mexican Fencepost, covering the tops of the posts with an old t-shirt, foam cup or wash cloth can help prevent frost damage. Watering plants the night before a frost can also help them stay warmer. Dehydrated plants are more susceptible to frost damage.

To Prune or Not to Prune?

If frost impacts your plant material, it is optimal to wait until the threat of frost has subsided to prune frost-damaged plants. Pruning away frost damage too early can result in additional damage to the plant if it is hit by frost again. New and un-established shrubs or ground cover plants are more susceptible to permanent damage and could be lost due to cold weather. Established plants with a sustainable root system can handle minimal pruning for aesthetic reasons throughout frost season.

When it comes to trees, some species like Ficus are particularly sensitive to frost damage. Many smaller trees may be lost all together and, unless particularly protected, significant portions of the larger trees may be severely damaged due to hard frosts. While it is hard to be patient, it is best to wait to see if new growth will come back. If you decide to prune the dead tissue, it will take years before it grows to its original size. If you decide to leave it, the green will eventually fill in, but you’ll be looking at brown dead tissue for several years.

No matter what steps you follow to prepare for cooler weather, it’s important to take proactive measures to prevent any loss of plant material, irrigation components and ultimately, your money, during the winter months.

For more information on desert landscape and plant care, check out Arizona Cooperative Extension. If you reside elsewhere in the southwest, contact your local Cooperative Extension office.

Flatheaded Borer

A Wood-boring Beetle

larvae and adult LCThe flatheaded borer is a metallic wood-boring beetle that can do major damage to your trees, even killing young trees. The adult borer lays eggs in crevices or injured areas of trees. The larvae that hatch immediately start to bore tunnels in the wood just under the surface of the bark, which is what they feed on. As the larvae grow they continue to tunnel through the tree, digging deeper and deeper to reach fresh moist wood.

Recognizing an Infestation

Larvae Excavation LCThe borer beetle is identified by its metallic appearance, but their larvae do the most damage. The larvae’s body has a flat enlargement just behind the head, and are light in color. The tunnels made by the flatheaded borer larvae injure the tree and are filled with finely powdered sawdust. Their digging causes sap to flow and the affected area will appear wet. As these wet areas dry they may crack and expose the borers’ tunnels. The tunnels they create are winding and flattened looking with oval shapes at intersections. When the adult beetle emerges from the bark or wood it leaves a characteristic oval shaped hole.Tree Damage LCProtecting Your Tree Asset

insecticideThe best way to protect your trees is to prevent an infestation. By creating a healthy growing environment for your trees, you remove the opportunity for the borer to lay eggs. Proper pruning and care are essential to having and keeping strong, sound trees that can fight infestation.

If you do have an infestation, prune away as much of the infected area as possible and spot treat it by applying insecticide to the surrounding area. Insecticide will only kill the larvae if the chemicals can reach them just below the surface, but it will help to prevent any future invasions. Bayer Tree & Shrub Insect Control is an example of an insecticide that can be purchased at Home Depot to treat a borer infestation.

Catclaw Rust

There is a Fungus Among Us

CatClawYou may have noticed brown clusters growing on your Catclaw Acacia trees. Known as Catclaw rust, the fungus infects the terminal ends of branches and causes a distorted, bunchy growth. It produces spores on the leaves of the tree in the late spring and summer that eventually cluster together and appear dark brown in color. Unfortunately, the cooler temperatures throughout May and the beginning of June were ideal conditions for the fungus. The monsoon season brought higher levels of humidity, yet low levels of rainfall this year, allowing the fungal spores to spread readily and rapidly.


Is There a Treatment for the Fungus?

According to Dr. Mary Olsen, Plant Pathology Extension Specialist at the University of Arizona, there is no known effective and practical treatment for Catclaw rust. The fungus is a normal occurrence in nature and prompts a “survival of the fittest” environment among the trees. The fungus typically has a two year life cycle from the start of each new spore growth. Under favorable conditions, the outbreak could be similar next year.

Catclaw RustRemoval or branch pruning of the Catclaw Acacia is not advisable at this time. Eliminating the affected branches may further weaken the tree by creating an open wound during the growing season. Furthermore, the fungal spore can be easily spread through pruners and disseminated in air currents.

What Can You Do?

The good news is that the less-than desirable brown clusters can be removed when the tree is in dormancy (December through the end of February). Here are some guidelines for removing the brown clusters:

  • Infected branches should be cut off from the union of two branches only when the tree is dormant.
  • Do not cut in the middle of the branch or the fungus is likely to growth back.
  • Remember that it will take two years for the fungus to “run its course.” Fungus that appears next spring may take another 2 years to dissipate.
  • Trees that are completely infested should be removed from the landscape.
  • Continue to monitor your trees and have patience.

It is expected that most trees, unless heavily infested, will recover. For more information visit the University of Arizona Plant Pathology Extension website:

Planting and Caring for New Plants

Whether you want to add new plants to your yard or you’re replacing plants you lost to winter’s freezing temperatures, now is the time to plant to give them the best chance of surviving the summer heat.

Shrub and Tree LandscapeIdeally, new plants should be installed when nighttime temperatures are over 55 degrees for a prolonged period of time and daytime temperatures are less than 90 degrees. For our desert landscape, plant replacement is most successful in the early spring because temperatures and humidity allow the plant to establish itself in its new environment before the harsher summer weather arrives. Certain tree species like acacia salicina and the desert willow demand spring planting because they establish new roots very slowly.

When choosing your new plants and trees, ask yourself these following questions:

Is it the right plant/tree for the right space?

How big is your plant or tree going to be in its mature size as it relates to its space? Does it have thorns that could grow into the common areas and sidewalks?  Do the roots have enough space to find the nutrients it needs? Expect trees to have root systems that reach out underground has far as its canopy extends.

What kind of light does it need?

The closer that the plant is to those hard surfaces like sidewalks and brick walls, the more sun and heat it will absorb. Be cautious of placing plants near these reflective surfaces.

How much water does it need?

Young plants will need more water as they root out looking for nutrients in the soil. Look for signs of distress like wilting or curling of leaves, leaves losing their color, and dead stems as signals of needing to water more. Also consider possibly using mulch or fertilizer to boost the young plant’s growth.

A young tree will need to have more emitters located near its trunk initially. These emitters will need to be moved from the trunk on a yearly basis to encourage the spread of the roots as the tree matures.

Frost Damage – Tree Recovery

Recent cold fronts moving through Phoenix have caused widespread frost damage throughout the Valley — particularly in Ficus and Sissoo trees. If you’re noticing signs of frost damage in your trees, we have some tips for restoring their health.

Patience is key

Frost Damaged TreeTrees with frost damage will require time and patience to nurse back to health. If you wish to recover your tree, the key factor is to give it time and provide it with the appropriate amount of water consistent with normal growing needs. Though a tree may appear unsightly and heavily damaged above ground, its root systems are durable and likely remain healthy and ready for new growth. First, focus on the restoration and recovery of your tree. Once your tree has made its recovery, you can  then focus on aesthetic pruning. It could take several seasons — but with the appropriate level of care — your tree can make a full recovery.

Caring for frost damaged trees

When the threat of frost has subsided and new growth has begun, its time to begin pruning. Start by doing a scratch test. To perform a scratch test, simply use your fingernail or a pocket knife on the trees smallest twigs and branches to determine the extent of the frost damage. If the wood is healthy, the tissue or flesh of the plant will reveal a green color. If you find brown or black tissue, this means the branch is dead. You will need to continue your scratch test on larger twigs and branches until you find where the green tissue begins. Once you identify where the healthy tissue begins, you will want to prune up to that point.

Proper pruning

If you decide to prune your tree yourself, its critical that you be properly equipped. Having the right tools to prune your tree is important to the health of the plant material.

Limbs up to ½ inch in diameter can be pruned with hand pruners. Long-handled pruning loppers can handle limbs up to 1 inch in diameter, but a special pruning saw is needed for larger limbs. Hand pruners and loppers should be of the scissor or bypass type rather than the anvil type. Hedging shears or power hedge trimmers should not be used to prune trees because they will not be able to make proper cuts and will damage the tree.

It is a good idea to wear a long-sleeved shirt, long pants and closed shoes when pruning; additionally, wear safety glasses, a hat and gloves to help prevent an injury. Unless you are a trained tree worker, avoid using a ladder or climbing a tree to trim it. Most importantly, never attempt to prune a tree that is near a utility line!

Frost Damage: Ficus Trees

The Dreaded FreezeFicus-2

When cold air fronts move through the Southwest, temperatures plummet and frost sneaks up on many of our sensitive plants and trees. Ficus trees are no exception.  Many smaller Ficus trees may be lost all together and, unless particularly protected, significant portions of the larger trees may be severely damaged due to hard frosts.

While it is hard to be patient, it is best to wait to see if new growth will come back. By the middle of May it will be evident if any new growth has emerged. If it has, it is generally found at the center and lower portions of the tree.

What To Do With Ficus Trees?

What can be done with a partially green Ficus tree? You can prune the tree by cutting just above the last buds. This process may take out the majority of the original tree but with continued corrective pruning and time the tree may, baring additional hard frosts, recover to an acceptable level.  Depending on the original size of the tree and the amount of damage, the right decision may be to remove it. Hiring a Certified Arborist to properly evaluate and perform the work is recommended.  A list of arborists can be found by visiting:

To Prune or Not To PrunePruned-Ficus

It’s difficult to look at your half green Ficus tree knowing that it used to be full, healthy and beautifully green. Unfortunately, your tree will never be the same no matter what you decide to do. If you decide to prune the dead tissue, it will take years before it grows to its original size. If you decide to leave it, the green will eventually fill in, but you’ll be looking at brown dead tissue for several years.

Trees vs. Monsoons

Heavy rains and strong winds associated with severe weather pose a significant test for 08-04-05 Tree Work (2)trees that are less than two years old. Frequently, these trees have never before shown signs of weakness or root problems. Although most trees remain unscathed during storms, a small percentage of trees lean or fall during as a result of wind and rain. This is usually a result of un-established or defective root systems.

Immediately following a storm event, DLC maintenance crews visit each damaged tree to determine the best course of action. In the process of evaluating a tree, the base of the tree and its root system is tested for strength and stability. This is done by moving the trunk slightly from side to side to determine if the roots exhibit some degree of establishment with the adjacent soil. Trees that show any degree of root stability are straightened and re-staked. Trees that show no stability, which means they are either broken at the base or root bound (essentially swiveling in the soil), are removed.

Root bound trees can usually be identified by observing the soil when gently shaking the tree. If the ground around the base of the tree moves, chances are the tree is root bound.

Root bound trees can usually be identified by observing the soil when gently shaking the tree. If the ground around the base of the tree moves, chances are the tree is root bound.

Root bound trees may live if re-staked and may continue to show above ground growth. However, experience tells us that these trees will eventually fail since root bound trees never establish good root growth. If root bound trees are re-staked instead of removed, there is significant risk that they will outgrow the stakes and fail again, this time as a larger tree. This can cause significant damage to whatever is in their path.

In locations where trees are removed, replacement trees are selected to include the best quality given the availability and variety. Depending on these factors, some replacement trees will be 15 gallon, 24” or 36” box size. It is important to note that where smaller trees are chosen, they will grow stronger in time because they have more growth time in their new location.


Poorly established root system allows a storm to knock over this tree


Girdled roots or a poorly established root system can cause trees to fail at the point of connection


Roots wound tightly around the trunk are called girdled roots. This will eventually kill the tree


Nursery containers can cause roots grow in a continuous circle


Ideal root growth – roots grow out in every direction almost evenly