Monsoon Season: Ready or Not Here It Comes!

With summer temperatures creeping into the triple digits, Monsoon Season is just around the corner. Summer monsoon storms offer much needed rain to our desert environment, but also pose the biggest weather related risk for trees. If not pruned and thinned properly, your trees are more likely to become the victim of high monsoon winds.

Now is the time to assess your trees to determine if they are in need of pruning before the monsoon storms arrive. If you didn´t prune your trees in the cooler months, it is prudent to do the work before the storms arrive. In preparation for monsoon winds, the tree´s canopy should be thinned so wind can pass through the tree easier. Typically, most pruning involves lifting a tree´s branches to a height that people can walk under. When monsoon winds arrive, the tree´s canopy is top heavy because the weight of the trees is concentrated above a certain height. Assess your trees in the upcoming weeks and remove overly thick foliage, correct damage from previous storms and remove dead or structurally unsound branches to minimize the chance the tree will be damaged or cause damage during a storm.

Having proper tools to prune your tree is important to the health of the plant material. Limbs up to 1/2 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. 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.

Before and AfterIn spite of the damage these summer storms can cause, there is a silver lining to the monsoon clouds: moisture! The monsoon presents us all with a great opportunity to save water. We assess the amount of water each storm brings and suspend or adjust irrigation schedules appropriately. Not only is rainwater free, it is also superior to irrigation water due to its lower alkalinity. In addition to providing moisture, the rainwater helps leach accumulated salts away from the roots of shrubs, trees and turf.

Following a storm, check the status of your irrigation controller. Power outages can reset irrigation clocks and schedules, and it may not be appropriate for the weather. If your property receives a substantial amount of rain, turn off your irrigation system. Be aware of your plant material and soil moisture in order to determine when the water needs to be turned on again. Overall, you may not need to water as much as you did in the drier months.

Mexican Fencepost

Pachycereus_marginatus_Wikimeda Photo

Source: Wikipedia Commons

What Is A Mexican Fencepost?

Mexican Fencepost is a quick-growing cactus that develops in a columnar manner and can reach heights of up to 20 feet tall and spread by up to 6 feet. Native to Southern Mexico, these cacti require very little watering, enjoy year-round sunlight, tolerate intense heat, and can survive temperatures as low as 20 degrees Fahrenheit. The Mexican Fencepost is often used, as the name suggests, as a fence or barrier. They can produce greenish-pink flowers that bloom from March through April. These flowers become edible, dark-red, very sweet fruits.

How Do I Care For My Mexican Fencepost?

Pest Control

Mexican Fenceposts are prone to attacks from scale insects. While there is no widely accepted treatment for preventing these attacks, many pest control companies offer removal services. Timely removal of pests often results in a full recovery for the cactus. Identifying the problem before it’s too late is key. By taking the following steps, you can minimize the risk of losing your Mexican Fencepost to pests:

  • Routinely check your cactus for scale insects. This can be done by purchasing tacky cards from your local home improvement store and placing them at the base of your cactus. If the cards fill with scale insects, you will need to call a pest control service to have the insects removed.
  • During the winter months, the scale insects seek shelter to avoid being killed off by the cooler temps. By keeping the areas around your Mexican Fenceposts free of debris, clutter, weeds, etc., the scale insects will have nowhere to go and will be eliminated by the winter weather.

Cold Temperatures

Mexican Fencepost is frost sensitive. If frost is in the forecast, cover the top of the cactus with an old t-shirt, foam cup or wash cloth. Water sparingly in the winter as it does not grow in cold weather.


Proper watering is essential to the health and vitality of Mexican Fenceposts. They are prone to rot if the soil is too moist or if kept in the shade with very little exposure to sunlight.

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: