TREES, PLEASE! Diamonds Are Not A Palm’s Best Friend

By Tim Clancy, for Let's Talk Plants! November 2021.

Tim Clancy
California Fan Palm with a full canopy.

Right tree, right place. This advice is really a warning that we should plan for the long term when planting trees. The Arbor Day Foundation has a page dedicated to this concept on its website. https://www.arborday.org/trees/righttreeandplace/


The concept is stressed by utility companies who do not want their transmission lines compromised by tree growth. Many of the fires in Northern California have been traced to transmission line contact.

What is typically stressed by the Right Tree, Right Place concept is the ultimate tree size. Will the tree you plant in your backyard become too large for the space at some point in its life. (I refer to this as the pot-bellied pig conundrum, remember them?) I have seen this on many occasions. In an attempt to delay the inevitable, sometimes the trees are heavily pruned to provide clearance from structures, or a root barrier is installed with the hope that the roots will be deflected and the tree can remain in place longer. When a homeowner is in a situation where a tree may outgrow its welcome I often ask, “How long do you plan to live here?” Many times, I inform people that the tree most likely will not create an issue for five or more years, so, if they intend to move, they can let the next owner deal with the issue.


There is another Right Tree, Right Place consideration as well. That has to do with the tree’s ability to grow and thrive in the area in which it is planted. The USDA has general climate zones for the country and there are further segmented climate zones for California. These are based on temperatures and are intended as a guide for choosing plant material appropriate for your location. Think tropical plants and frost for instance.


The California fan palm is a magnificent tree. I have seen specimens in the Palm Springs area that are stunning. The tree was important to the Native Americans that shared its habitat. They used it as a food source among other things. For some more information on this fabulous tree chase down a copy of James W. Cornett's book Desert Palm Oasis (Nature Trails Press, Palm Springs, CA: 2010).


Top photo is of diamond scale on a frond and the photo below it is a frond dead from diamond scale.


The WRONG place for a California fan palm is anywhere there is a coastal influence. Diamond scale, despite its name, is a fungal disease and not an insect. This disease afflicts only two hosts which are both palms in the Washingtonia genus. Despite the fact the Mexican fan palm is listed as a host I have not seen it on that palm species. I have however seen it on every California fan palm planted within areas of coastal influence.

Tim Clancy
Aren't these beautiful? NOT!

In Encinitas the palm was planted as a signature street tree in a recent housing development at the corner of Santa Fe Drive and Lake Street. I am sure that these plants were intended to make a statement and demonstrate the landscape architect’s ability at designing an outstanding planting plan. The statement I take away is somebody doesn’t know that these plants do not fare well under the coastal influence. What we are left with is a large scale planting that is declining and, in my opinion, unsightly. There is absolutely nothing that can be done to “cure” the palms and they will continue to decline for many years to come. Those of us who drive by them will have to watch them as they fade away.


Pure and simple it was a big expensive mistake to use that species in that location. The current price for those trees is $70.00 per trunk foot (Measured to the emerging growth spear). Now include in that the installation costs (conservatively $1,000 per tree) and you can see they are expensive. Now include the removal costs and replacements with a different plant and, wow, what a goof up. I am not sure if those are HOA trees or city trees but either way the architect or developer are not paying for the mistake. Either the HOA or Encinitas taxpayers will foot the bill. And until someone is insistent they get replaced, (is that years away?) we will have to watch them die.


Tim Clancy, Tim Clancy & Associates LLC


P.O. Box 1180


Cardiff-by-the-Sea, CA 92007

- International Society of Arboriculture Certified Arborist No. WE-0806A


- International Society of Arboriculture - Tree Risk Assessment Qualified