Tree Care

Trees in the Landscape

Trees play an important role in our landscape and provide a multitude of benefits for humans, wildlife, and the environment. They provide shade, habitat, oxygen, food, and can help us conserve energy and water if properly selected and cared for. Trees are woody stemmed, perennial plants that are typically long lived. The more mature the tree, the greater the amount of benefits they provide. It’s important to remember that they are a living organism that needs to be cared for properly throughout its life cycle.

Major funding for this project is provided by CAZCA, the Arizona Department of Forestry and Fire Management’s Urban and Community Forestry Program, and the USDA Forest Service. These institutions are equal opportunity providers and employers.

Table of Contents

This page has a lot of information, so we’ve created a hyperlinked table of contents so it is easier to find the specific information you need.

Tree Selection – Right Tree Right Place

Tree Planting

Tree Care

When To Call an Arborist

Tree Selection

Trees play an important role in our landscape and provide a multitude of benefits for humans, wildlife, and the environment. They provide shade, habitat, oxygen, food, and can help us conserve energy and water if properly selected and cared for. Trees are woody stemmed, perennial plants that are typically long lived. The more mature the tree, the greater the amount of benefits they provide. It’s important to remember that they are a living organism that needs to be cared for properly throughout its life cycle. 

Tree Selection – Right Tree Right Place 

If you are looking to add trees to your landscape, the planning process starts before you get to the nursery. It’s important to think about why the tree is being planted and what purpose it will serve. Are you looking for shade, food, privacy? It’s also important to understand the space in which you plant the tree. How much space do you have, what is the soil like, are there pipes underground to avoid? If you have a certain species you want to plant, how tall does it get? How wide is the canopy, and what is the typical root structure? 

Before you decide to plant a tree, consider the following:

Space Requirements: Is there anything overhead or underground? What is the size of the space? Call 811 before you dig.

Soil, Sun and Moisture Availability at the Site: Make sure to pick a species that is compatible with the factors of the site, and that there is water and nutrients available for the tree. Know the Hardiness Zone of your area, and make sure the tree can survive the year-round climate. 

Tree Shape: When selecting a species, make sure to consider the future growth of the tree, both above and below ground. Mature canopy size, shape, height, and characteristics like fruit or thorns can all play a role in determining the best tree for a location.

Planting your Desert Space for Water Conservation and Efficiency

When a tree species and location for planting are properly selected, trees can contribute to energy savings in our home by shading our structures from the hot sun, and capturing stormwater runoff, slowing down the water and allowing it to benefit the local ecosystem. These features also support a healthy understory of plants and provide refuge for wildlife.

Native Trees

Why native

Native plants work together to protect biodiversity and stewardship of cultural heritage. Arizona native trees are better suited for the Sonoran Desert climate and soil conditions, are more resistant to drought, and require little care. Aside from the benefits native trees provide to us, they also create habitat for native wildlife and pollinators, and contribute to genetic diversity; more genetic diversity results in more resilience to environmental stresses such as pathogens and pests. 

Which trees are native

All of Arizona:

• white fir (Abies concolor) 
• cat claw acacia (Acacia greggii)
• white thorn acacia (Acacia constricta)
• boxelder maple (Acer negundo)
• water birch (Betula occidentalis)
• netleaf hackberry (Celtis laevigata var. reticulata)
• western redbud (Cercis orbiculata)  
• desert willow (Chilopsis linearis)
• Arizona cypress (Cupressus arizonica)  
• singleleaf ash (Fraxinus anomala)  
• Arizona ash (Fraxinus velutina)  
• Arizona walnut (Juglans major)  
• alligator juniper (Juniperus deppeana)
• one-seed juniper (Juniperus monosperma)
• Rocky Mountain juniper (Juniperus scopulorum)
• flowering crabapple (Malus sp.)
• desert ironwood (Olneya tesota)
• blue palo verde (Parkinsonia florida)
• foothills palo verde (Parkinsonia microphylla)
• blue spruce (Picea pungens)
• pinyon pine (Pinus edulis)
• ponderosa pine (Pinus ponderosa)
• Arizona sycamore (Platanus wrightii)
• Fremont cottonwood (Populus fremontii)
• narrowleaf cottonwood (Populus angustifolia)
• quaking aspen (Populus tremuloides)
• velvet mesquite (Prosopis velutina)
• screwbean mesquite (Prosopis pubescens)
• chokecherry (Prunus virginiana)
• Emory oak (Quercus emoryi)
• Gambel oak (Quercus gambelii)
• shrub live oak (Quercus turbinella)
• New Mexico locust (Robinia neomexicana)
• black locust (Robinia pseudoacacia) 
• Goodding’s willow (Salix gooddingii)

Under 4500’

• velvet mesquite ( Prosopis velutina)
• screwbean mesquite ( Prosopis pubescens)
• desert ironwood ( Olneya tesota)
• cat claw acacia ( Acacia greggii)
• white thorn acacia ( Acacia constricta)
• netleaf hackberry ( Celtis laevigata var. reticulata)
• foothills palo verde ( Parkinsonia microphylla)
• blue palo verde ( Parkinsonia florida)
• desert willow ( Chilopsis linearis)

Characteristics of the trees

Arizona native trees possess many unique characteristics including distinctive structures and aesthetically pleasing color palettes.

Native trees also have large root systems that help reduce soil erosion.

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Tree Care

Watering 

Best watering practices (drip line, frequency)

Drip irrigation systems are highly recommended for arid/desert climates because they water plants slowly, at low pressure, over a long period of time, which allows the plants to absorb more water, thus reducing excess runoff and evaporation. These systems are ideal because they can be easily regulated and are placed strategically to avoid watering unwanted plants. 

Watering frequency will vary depending on the tree species, and it is advised that you group species with similar watering requirements together when designing your landscape to ensure effective irrigation. 

Pruning 

Pruning is an important part of regular tree maintenance, but it can also be one of the most intimidating parts as well. Understanding why we prune is fundamental in tree care; we do not prune for the sake of pruning, instead we determine why a tree might need to be pruned. Are there dead branches? What about a fungus or some mistletoe? Any cut made on a tree leaves a wound that the tree has to expend energy trying to heal. That energy is taken away from other important functions of the tree. Knowing what to remove minimizes the amount of cuts needed to meet our why objective.

Structure, safety, biology, and aesthetics all need to be considered when developing a plan of what to prune on your tree, and understanding the facts about why, when, and how to prune will help the tree live a longer, healthier life.

Reasons to Prune

Tree Health: Removing dead branches can help speed up the healing process of closing off the trunk from the lost branch. Disease progression can be prevented by removing a branch that has evidence of an infection. Rubbing, crossing, or inwardly growing branches can be removed to prevent future wounds from developing.

Structure: Young trees are selectively pruned to encourage the development of a strong, central leader and preserve lateral branches that have strong attachments. At the initial planting and several years after, branches that are larger than half the trunk diameter should be shortened or removed since they will compete with the central leader and could form weak attachments as the tree matures. When done properly, structural pruning can reduce the need for frequent pruning as the tree matures and doesn’t respond to pruning as well as a young tree. 

Risk Mitigation: Trees can hold various risks, and recognizing potential conflicts is a main component of tree care. While removing large, dead branches is an obvious way to reduce risk, pruning can be also done for visibility and street clearance, reducing weight over structures, and tip reduction/wind resistance. 

Aesthetics: This can be done by enhancing the natural tree form, creating symmetry, clearance, or even selectively pruning to enhance flower production.

Tree maintenance is inevitable, but it is important to remember that trees are living organisms. Removing branches affects trees by reducing a trees ability to photosynthesize, reallocating stored resources, and impacts future growth. Trees react to their environment and stressors so a balanced maintenance plan is important. If a tree is requiring an excessive amount of maintenance, it is likely that the tree is not suitable for where it is planted.

Branch Structure and CODIT

Image would be beneficial here.

Trees have specialized tissue at the base of every branch called the branch collar. This specialized tissue is a protective chemical zone that equips the tree with the ability to ‘wall-off’ the wound to prevent decay and pests from invading inside the tree. You can recognize the branch collar by a slight bulge. It is important to make sure that this area is not damaged while pruning so that CODIT (compartmentalization of decay in trees) is able to take place.

Proper tools and sterilization practices

• • Pruning shears – These are one of the most common tools to have in the garden shed. Also referred to hand pruners or clippers, these should be used for branches up to ¾ inch thick depending on the tool specifications. 
• • Loppers – There are different strengths of loppers, but they are typically for branches 1”-2”. 
• • Pruning saws– These are handheld saws that vary in size. Depending on the size and shape of blade and species of tree, these saws are used to prune branches between 1-6 inches in diameter.
• • Pole pruner– The pole pruner is used for pruning limbs that you cannot reach from the ground otherwise, and is used for removing branches up to 2 ½ inches in diameter.
• • Pole saw – Just like a pole pruner, a pole saw lets you reach parts of the tree you wouldn’t otherwise be able to access. Like a hand saw, a pole saw is typically used for branches up to 6” in diameter. Much like the pole pruner, the benefit of this tool is the extended reach. 
• • Chainsaws and other power tools – if there is tree maintenance that requires the use of a chainsaw, it is best to leave that to the professionals and you should contact an ISA Certified Arborist
• • Tools should be cleaned and sterilized between trees to reduce the chance of infection. Diluted bleach or isopropyl alcohol are a couple of examples of suitable cleaners to sterilize your tools.

How to make a pruning cut

• • Make your first cut on the bottom of the branch away from the branch collar. This is typically about a foot away from the branch attachment, and prevents your second cut from stripping the bark from the trunk of the tree. Your second cut should be on the outside of the first cut and leave a stub. Your third and final cut should be cut right outside the branch collar to preserve it completely. This gives the tree the best chance to heal the wound.
• • The cuts made should be smooth. In the event that the cut leaves a jagged edge, an effort should be made to smooth it out. Images of good cuts vs bad cuts
• • Flush cuts are cuts that damage or completely remove the branch collar which destroys the tree’s natural defense mechanisms against decay. 
• • You can prune up to 25% of a tree’s canopy, but ideally you wouldn’t want to prune more than 10-15% if you don’t have to.

How to spot bad pruning

• • Topping is the poor, uninformed practice of removing the living crown (top) of the tree. While this practice is detrimental to the health of the tree, it also makes the tree riskier in the future. Topping sends a tree into survival mode and causes rapid growth of shoots to compensate for the loss of food source. This not only depletes the tree’s energy stores, but as those shoots grow larger they become prone to failure due to their weak, sharp angled attachments. The tree has a difficult time healing these cuts since they occur outside of the branch collar, and can leave tissue exposed to insects, disease, and decay. 
• • Lions-tailing is the practice of over pruning the inner branches of a tree leaving the limbs stripped which causes the tree to resemble a lion’s tail. The excess removal of the tree’s foliage starves the tree and can increase the risk of sunscald. This method also increases the risk of failure since it ruins the structure of the tree. Retaining internal branches allows limbs to dampen the force of winds, but when a tree is lion’s tailed it risks limbs snapping from high winds or excess tip weight.
• • Proper tools for the proper cut. It’s important to make sure you are using the correct equipment to prune trees. Having sharp, well-kept tools will give you clean cuts that are desired while pruning a tree. Dull tools or using tools that aren’t adequate for the size of the cut can lead to poor cuts that can be detrimental to the health of a tree.  

Palms

Palms are not trees but require a similar maintenance schedule. The dead leaves of a palm, fronds, can become dangerous if they are not regularly removed. As the fronds die, their attachment to the palm becomes weak and can fall to the ground. A palm frond can weigh up to 100 pounds, and people have been severely injured and even killed from falling fronds.  Palms can also be pruned in the spring to remove flowers to keep them from fruiting (e.g., dates). Allowing palms to fruit is undesirable to most due to the mess and potential hazards they can create. 

When to call a professional

While simple, light pruning can be accomplished by the tree owner, more often than not a professional will need to be called. Here are a few of reasons why you might need to call a professional arborist:

• • Large tree that requires climbing or and aerial lift
• • Extensive pruning
• • Presence of insects, disease, or decay
• • Risk mitigation or storm damage
• • Tree removal
• • Plant Health Care (PHC)

Working with and around trees can be dangerous, and if there is any hesitancy in work that needs to be done, it is best to call an ISA Certified Arborist. They will be able to perform the technical work that goes into tree maintenance and removal as well as give diagnosis and prescription for tree health issues.

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