Regional Gardening Reports :: National Gardening Association

In the Garden:
Northern California Coastal & Inland Valleys
July, 2007
Regional Report

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The metal band around the trunk of this palm tree prevents rodents from climbing the trunk and taking up residence in the canopy.

The Noble Palm

What tree shouts "California!" more loudly than the stately palm? Sunset Boulevard is lined with them, as are many thoroughfares in the state. Every Spanish mission along the El Camino Real has date palms flanking the entrance.

I recently had the opportunity to shoot several segments for Henry's Garden on the care and maintenance of palm trees. Henry, our cameraman Art Takeshita, and I arrived at the Lone Mountain campus of USF to find the Bartlett Tree Experts already hard at work on the Phoenix canariensis palms that line the drive. The trees are at least 75 years old and are professionally groomed every year. Grooming palm trees entails removing the old fronds that have turned brown, cutting out the faded flowering stalks, and "shaving" the pineapple. The trunks and the characteristic globe at the top that sprouts the fronds are "shaved" with a chain saw. It takes a skilled arborist to create that classic look.

Trouble in Paradise
I was surprised to learn that palms are a member of the grass family. I also learned that the palms here in San Francisco are in jeopardy from a fungus disease called pink rot, which attacks the crown of the tree. Palms, unlike other trees, have only one central growth point. This tender shoot is where every frond emerges. The pink rot attacks that tender new growth, killing it so that the palm has no terminal point of growth.

The moist, cool conditions in San Francisco are ideal for pink rot to take hold. Recently, many palms have been imported into the city -- for the new Embarcadero and Market Street renovation projects -- from desert regions where pink rot has laid dormant and not been able to take hold because of the dry desert conditions. Once these new palms are planted in San Francisco, the fungus disease comes out of dormancy and becomes airborne, spreading to other established trees throughout the city. The trees may not look dead, but once the older fronds fade, there is no new growth to replace it. There is no treatment currently available for pink rot.

Hurricane-Proof Plants
I asked how palms survive in areas where there are hurricanes. Juan Carrasco, one of the certified arborists working on the site, told me that palm trees have an extensive system of fibrous, interlocking roots that grow well beyond the area of the canopy. The leaves are designed to fold in upon themselves when the wind blows, creating a very small surface area. The flexible trunk is made up of fibers that also interlock -- overall, a very clever design for a tree meant to withstand winds over 100 miles per hour.

A Welcome Addition
If you have seen the palms along the Embarcadero you know how elegant these trees are and how valuable they are to the landscape. Phoenix canariensis is native to the Canary Islands and does produce dates, even in our mild climate. You will often see, and hear, the famous parrots of Telegraph Hill dining on the sweet fruit. The lush canopy is a secure home for birds, raccoons, and, yes, I'm sorry to say, rats.

Palms, although not native, are part of our landscape. Let's hope they find a cure for pink rot before we lose these magnificent trees.

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