Frost Damaged Plants in Arizona...

As I’m sure you’re aware, the cold weather is upon. Bitter nighttime temperatures have everyone huddling around heaters, outdoor fireplaces, or staying inside to keep warm. In the outlying areas of the Valley, some even have had to scrape frost from their windshields before heading off to work.

With an Arizona freeze, also comes the unsightly frost damage to many of our native desert plants. No longer do we see the bright Yellows, Reds, Greens, and Oranges, of our landscapes. Instead, we see browned out remnants of our once beautiful plants. While this is an ugly occurrence, frost damage is a normal process for our Arizona plants and landscapes.

Below are a few pictures of plants typically hit the hardest by Arizona frost:

Bougainvillea - Cape Honeysuckle - Gold Mound Lantana

 

Frost damaged Ficus in Phoenix Arizona

Arizona trees are no exception to the frosts ability to strike. At the left is a picture of a large ficus tree in Phoenix damaged by our nighttime freeze.

While there is a sense of cleanliness to trimming off this burnt, deathly looking material from the plants, it is NOT recommended. The dead plant material, surrounding the inner portion of the plant, acts as a blanket keeping the plant warm throughout the remaining threats of frost.

If trimming must be done, a light trimming of the outer 20% of the plant may be done to keep the plant in an aesthetically pleasing shape. Cutting more than this recommended 20% may cause injury to the interior, not yet frozen or damaged, portion of the plants energy system.

Once the threat of frost in Arizona has passed (typically around February 14th), pruning back plants can be done with relative success. This will be the time to trim off any frost damaged portions of our plants like Lantanas, Bougainvilleas, Oleanders, Honeysuckles, or Natal Plums. It is important to remember that once the plant has been trimmed back, the built up bio-matter trapped around the base of the plant must be removed as well. This bio-mass of decomposing plant material limits the amount of oxygen the plant uses for respiration. Removing it will help with nutrient uptake, the natural cooling process of the leaves, and strength of the roots. Be careful not to damage the base of the plant when removing the decomposing material as the outer layer of the plant in this area is very sensitive.

After frost pruning has been completed, a light application of a balanced slow-release fertilizer is recommended. 6-20-20 is what we use. This can be purchased at your local nursery, as they can help explain the proper rates at which to apply the product.

With a little patience and timely Arizona landscape management practices, the beauty will soon return to our Native Arizona plants. The smell of spring will be enhanced by the fragrance from our flowers and trees as they recover, naturally, from the long and cold winter months. Soon, spring will be here…

Have a great and safe New Year!

Scott Cosgrove  ISA Certified Arborist in Arizona, CLP, CDLP, ACPA, CTM
ProQual Landscaping