In the Philippines they say if you could count the stars then you could count all the ways the coconut tree serves us; this aphorism holds true for the usefulness of so many palms.
There is an old riddle that goes like this: if you drive a nail into the side of a tree five feet above the ground, and the tree grows one foot per year, how high off the ground will the nail be if you return in 20 years? Like many riddles, this one is a trick question. In 20 years the nail will still be five feet above the ground; in 200 years it will still be five feet above the ground. Trees only grow in height at their tips and outward at their trunks. Trunk tissue does not move upward with age.
The classic answer to this riddle was recently challenged in the pages of the May 2012 issue of the American Journal of Botany when researchers at Boston University discovered that the South American stilt palm (Iriartea deltoidea) has a trunk that actually moves upward as the tree gets older. As it turns out, tightly coiled fibers in the trunks of young palms expand with age, pushing the whole trunk upward—a truly novel growth mechanism! A nail in the side of this palm will slowly rise with passing years.
This recent finding adds to the many reasons palms are botanically and horticulturally amazing. While they do not grow annual rings of wood like broad-leaved trees and conifers from temperate climates, palms are trees nonetheless, with large, single trunks and sizable canopies. Most palms have an undivided trunk that does not widen with age and a single growing tip from which all the leaves arise. If the single apical bud inside the growing tip is damaged or frozen, the entire trunk will die. Some palms can grow to be extremely tall, like the Andean wax palm (Ceroxylon quindiuense), which reaches nearly 200 feet. The vining rattan palms (including Calamus spp.) have the longest stems in the world, some nearly 600 feet long.
Wonders of the natural world, palms are beautiful, distinctive, and charismatic architectural elements in the landscape. Over 100 species of palms are widely grown as ornamentals. Several species yield energy-rich fruits including dates (Phoenix dactylifera), açaí (Euterpe oleracea), oil palm (Elaeis guineensis), and what some have called the world’s most used and useful plant: the coconut (Cocos nucifera). The apical buds of several species are harvested for their edible palm hearts; sugary sap from others is drained for beverages, and palm leaves, stems, and trunks are used in roof thatching, furniture, weaving, and construction. Many of the 2,600 or so species are frost-tender, from subtropical and tropical parts of the world, but there are numerous hardy palm species from upper latitudes and altitudes.
I recently chatted with Bay Area palm expert Jason Dewees about his favorite hardy palms for West Coast gardens. Jason is a horticulturist, one of the innovative forces behind the iconic San Francisco nursery Flora Grubb, and as the one-time youngest member of the International Palm Society, an all-around palm nut. Jason prides himself on dispelling commonly held myths that palms are only suitable for tropical gardens, make anywhere they’re planted look like Los Angeles, or are too big for small gardens.
Jason advises gardeners to avoid using palms in stale geometric, symmetrical, or regimented formal designs. Instead, try palms as vertical elements that still allow light into small urban gardens; plant a small grove, or substitute for bamboo. Palms make striking features in container plantings and complement dry Mediterranean, California native, or succulent garden tapestries. Jason’s even a proponent of creating handsome and unusual hedges with palms. No matter how you incorporate them, Jason’s favorite palms deserve more attention in Western gardens.
Jason’s Palm Picks
Chilean wine palms
(Jubaea chilensis), from ravines and ridges of dry scrubby woodlands of central Chile, are the thickest-trunked palms in the world. Once cut, a sugary sap flows from its massive trunk yielding hundreds of gallons of syrup for nearly two years. In Chile, where the palms are now protected and rarely felled, this syrup was once fermented into a sweet wine. Chilean wine palm fruits, called coquitos in Chile, are also edible and similar in appearance and taste to small coconuts. Old Chilean wine palms can be found throughout coastal California. Slow growing when young, they eventually mature into an impressive specimen.
The Sonoran blue palm
(Brahea armata var. clara) has silver-blue, fan-shaped leaves, a stout gray trunk, and enormous cream-colored flower clusters (up to 20 feet long) that arch spectacularly from the center of the canopy. Drooping leaf tips distinguish variety clara from the species. This is a steadily growing palm that makes a great container specimen when young and a breathtaking garden focal point when mature.
The blue Mediterranean fan palm
(Chamaerops humilis var. argentea), native to the Atlas Mountains of Morocco and western Algeria, is a striking variant of the typical green Mediterranean fan palm with deeply divided, bluish silver leaves. This extremely hardy and easy to grow palm can tolerate temperatures at least as low at 10ºF. It naturally forms a low clump, with new shoots and leaves arising from ground level, but can be trained to a single trunk. It is well suited for a container, tolerates wind and drought, and has wickedly spiny leafstalk margins.