If palm trees make you think of tropical sun and white sugary beaches, it's understandable. Palms have become a symbol for warm coasts and tropical vacations. Most palm trees do, indeed, like warm climates, and thrive in U.S. Department of Agriculture plant hardiness zones 8 through 10. But palms are of the Arecaceae plant family with 181 genera and 2,600 species, and include many and diverse species found everywhere from deserts to rain forests. Most palms have fronds -- large, compound, evergreen leaves arranged at the top of an unbranched trunk. But palms vary in many ways too.
With so many species, it's hard to get an overview of the palm tree family. One way to divide the types of palm trees into more manageable categories is to consider the two types of leaf structure: These are palmate and pinnate. A leaf that is palmate has lobes fanning out from one point, not unlike fingers radiating out from the hand. It is shaped like a fan. More cold-hardy palms tend to have palmate leaves. If individual leaflets branch out on both sides of an axis, like a feather, the leaf is termed pinnate. Most tropical palms have pinnate leaves.
Palms with palmate leaves include lady palm trees (Rhapis excelsa), that grow to 8 feet tall; Puerto Rican thatch palm trees (Coccothrinax alta), growing to 25 feet; and silver saw palmetto palm trees (Acoelorrhaphe wrightii) that grow to 20 feet tall.
Palm trees with pinnate leaves include mountain cabbage palm trees (Prestoea acuminata var. Montana), shooting up to 25 feet; majesty palm (Ravenea rivularis or Ravenea glauca); queen palm trees (Syagrus romanzoffiana), growing to 50 feet; and date palm trees (Phoenix dactylifera) that grow to 50 feet and produce dates.
Types of Palm Trunks
Another way to distinguish palm trees is by their trunk types. There are three palm tree trunk types. They are:
- Solitary trunk. This is the best known palm trunk type.
- Clustered trunks. You'll see clustered trunks when palm trees with thin trunks grow in a cluster.
- No trunk or underground trunk; the leaves grow directly
from the ground.
Palm tree size can also be helpful in distinguishing palms. Some palm tree species can reach a height of 200 feet, as is the case of Quindio wax palm (Ceroxylon quindiuense), the tallest palm tree in the world. It is native to the high altitude Andes in Colombia. A closer-to-home tall palm is Mexican fan palm (Washingtonia robusta), which is emblematic of Los Angeles and tops out at 100 feet.
Palm Tree Roots
Although palms can be hundreds of feet tall, their roots generally grow in the top 36 inches of topsoil where water and nutrients are plentiful. They do not have long, deep taproots like some trees (oak, for example). Instead, they grow dozens of very thin roots that grow outward horizontally from the tree base. They stabilize and anchor the palm and grow into soil for sources of nutrients and moisture. Palm roots grow outward for great distances, not just a few feet from the trunk. Tall palm species -- such as royal, Bismarck, Bailey and Canary Island date palms -- grow roots up to 50 feet away from the trunk.
Palm Tree Growth Requirements
Growing palm trees isn't difficult if you have the correct information on a particular tree and determine its optimum growing conditions. Be sure you choose an appropriate palm tree for your climate, and then plant it in a spot where it gets the sun exposure that works best for the individual species. Take into account the mature size of the tree when you are choosing a site.
After you transplant your palm, be sure to keep it watered well. Wrap a soaker hose around the root area to keep the soil moist. Only after the tree's roots are established should you reduce watering to 15 minutes twice a month.
Palm trees require nutrients, so if you plant a palm, it's up to you to get the tree sufficient magnesium, iron and manganese. These protect the fronds and prevent them from yellowing. Use a plant food made for palms. Apply it in spring, then again three months later. If you use a granular fertilizer, work it into the soil around the roots, then water the area well.
From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.