Pruning 101: Correct Palm Pruning

(Updated 10/19) There are major problems in the land of pruning, according to arborists certified by the internationally recognized organization, the International Society of Aboriculture (ISA).

Many tree pruners remove excessive live parts only to be doing paid work, says San Bernardino Certified Arborist Paul Chaney.  “This is unethical, and it damages the tree — the customer’s property.  Many large, mature, and valuable trees are being severely damaged [in Southern California] because of ignorant and unethical tree cutters,” Chaney says.

In this article, we will address palm pruning (next will be regular trees, with an emphasis on mature trees).

Internationally recognized standards called the ANSI (American National Standard for Tree Care Operations) A300 standards dictate you should not remove fronds below the bud (or the heart of the palm where leaves emerge). However, you commonly see palms ‘rooster-tailed’, which is leaving only several upward fronds. Even our City of Redlands often overtrims palms — but has improved recently.

Why It’s Important to not Overprune Palms

The common reason for overpruning palms is they’re tough trees and can take it. But overpruning stresses all trees, making them more susceptible to disease, and can especially affect the structure of palms.

“Energy to mass ratio gets tighter as trees gain more mass that they have to maintain,” explains Chaney, who said you can see the narrowing of the palm’s trunk after severe pruning.

This is especially evident in the older, skinny Washington fan palm (Washingtonia robusta), which are native to southern Baja California. “Old, tall W. robustas need to have only dead leaves, flowers, and fruit removed.  They need all the green they can maintain in order to support that tall, massive trunk,” says Chaney.

Chaney said slower-growing palms, like the Mexican fan palm (Brahea armata) and Guadalupe palm (B. edulis) can suffer.

Overpruning can even cause palms to die. Again, Chaney gave local examples. One was a Canary Island date palm at the Morey Mansion on Terracina in Redlands, which had a matching mate on the right side of the front. “But both were overpruned.  They both developed severe narrowing in the trunk, and the one on the right failed after the crown re-grew and became too heavy for the weak spot,” he says.

Chaney said the A300 standards are a starting point.  “For palms, it says nothing above the bud should be cut, but on massive, old, tall, or slow growing palms, only the bare minimum of green should ever be removed,” says Chaney.

Response from ISA 

I sent photos of overtrimmed palm trees to Alex Julius, ISA’s Educational Development Manager and a certified arborist. Her response:“from the pictures you have provided, the palms have clearly been overtrimmed. The only thing that would warrant pruning this extreme would be interference with utilities or diseased, dying fronds.”

She went on to explain that the standards for palms (ANSI A300 Part 1) states that 1) Live, healthy fronds should not be removed, and 2) Live, healthy fronds above horizontal shall not be removed. The exception is palms encroaching on electric supply lines.

Wildlife Concerns Dictate When to Prune

Susan Sims, an ISA certified master arborist and owner of Sim’s Tree Health Specialists in Riverside, agrees that palms are overpruned.  She also recommends pruning palms in the winter. Avoid pruning in spring through fall for two reasons.

First, pruning during the hottest months is hard on all trees. But  the primary reason is that you’re removing bird habitat, “the trees protect the birds and the trees are healthier too,” Sims says. In California, harming nesting birds is illegal  – see When to Trim Trees and Protect Nesting Wildlife about the regulations that protect birds.

She witnessed how the fan palms on her property became nesting areas for orioles once she stopped the overpruning practice of the former owner. There are significant fines for disrupting nesting birds. March 15th through September 15th is the recognized annual nesting season for California native birds.

Finding Good Tree Trimmers

The Problem! “Even a licensed tree contractor isn’t required to know anything about trees”  – Paul Chaney, ISA Certified Arborist, First Certified Arbor Care

Your best bet is find someone who is ISA certified, which requires many years of training and passing an exam. “Even a licensed tree contractor isn’t required to know anything about trees,” says Chaney, whose company is First Certified Arbor Care. So the typical tree trimmer who knocks on your door is not aware of the standards and doesn’t think they are doing poor jobs.

Other  tips:

1) ask to see a copy of their business license with the city

2) get photographs of past work, and

3) get more than one bid, and be prepared to pay a little more for a better job.

4) also educate them. One handout on palms is available online – with one here.  Proper pruning is easier on the tree, and there’s less yard waste to cart away.

For more info, this Dave’s Garden article “Pruning Palms” is a little old but has good information on various palms and proper trimming