If you want a exotic tropical look to your yard or garden, you can choose from numerous elegant palm trees that evolved in warm, subtropical or tropical climates. You may encounter one of more than 185 species on the market out of about 3,000 species in 200 genera worldwide. Palm tree roots are markedly different than those of standard deciduous and evergreen trees, making them easier to transplant.
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Broadleaf and evergreen trees typically have a tap root or a few large primary roots that grow from the base of the trunk. These roots grow larger in diameter as they branch outward and downward forming a network under the tree. Palm trees do not have a woody tap root. A palm tree grows a large number of roots from its base, forming a root ball that supports the tree. These are called adventitious roots, and they are as wide as they are going to get as they emerge from the bottom of the stem. They may branch up to three or four times, but the branches are increasingly smaller. The third and fourth branches are the thinnest and they grow upward in search of water and nutrients.
Roots and Climate
As palm trees age, they grow new roots from the base of their stem or trunk. Species that grow extremely tall occasionally grow roots above ground to help prop them up. Many palms that evolved in rain forests and forest undergrowth have shallow roots that spread across the forest floor. Roots of palms that evolved in the open grow deeper for support. Palms that evolved in arid climates also grow deeper roots to obtain moisture.
The nature of palm tree roots makes it easier to transplant a tree grown in a nursery container. You don’t have to worry about pruning roots that wrap around the inside of the container. Dig a hole that is twice the size of the container. If you plant it level with the ground it may topple over. The area where the roots grow from the stem of the tree should be about 1 inch below the ground. Look for a nursery transplant with the largest possible root ball. If you want to plant a tropical species, one that grows in U.S. Department of Agriculture plant hardiness zones 9 through 11, the soil temperature should be at least 65 degrees Fahrenheit for the roots to thrive.
Palm Tree Growing Zones
Palm trees may have a tropical look, but they grow in a wider range of climates than you might expect. Tropical and sub-tropical species grow in USDA zones 9 through 11. Most species in the Brahea genus will grow in USDA zones 8 through 11, while many species in the Sabal genus will grow in USDA zones 7 through 11. Dwarf palmetto (Sabal minor) will grow in USDA zones 6 through 11. Species in the Trachycarpus genus will grow in USDA zones 6 through 11. Needle palm (Rhapidophyllum hystrix) will grow in USDA zones 4 through 11.