Palms grow in well-watered zones of the world but are most prolific in tropical and subtropical climates. They are often thought to impart a "tropical" appearance to a landscape. With more than 2,000 species available, it is possible to select palms suitable for a given location and purpose. And, with proper care, palms can enhance many landscapes.
Palms are commonly considered to be trees, although botanically they are different. Their growth, appearance, and care vary considerably from trees. Most palms have a single trunk (coconuts), though some species grow as clustering or clumping palms (fishtails).
A palm has a single growing point at the top of its trunk. This point and its surrounding tissues are called the terminal bud. If the terminal bud is injured, the palm may die. The roots of a palm do not thicken like those of trees, so palms are less likely to damage sidewalks and utilities. The roots generally live for a few years and then die. New roots are generated at the root initiation zone, which can sometimes be seen above the base of the trunk.
Considerations for selecting a palm are similar to those for selecting a tree. A number of factors should be considered:
Why is the palm being planted? Will it act as a windbreak or screen (clumping palm)? Will it be a focal point to the landscape? Maybe more than one reason?
What is the size and location of the planting site? What is the hardiness zone? Is it sunny or shady, windy or protected? Does the space lend itself to a large, medium, or small palm? Are there overhead or belowground wires or utilities in the vicinity? Do you need to consider clearance for sidewalks, patios, or driveways? Are there other trees in your area?
Which type of soil conditions exist? Is the soil deep, fertile, and well drained, or is it shallow, compacted, and infertile?
How much maintenance are you willing to provide? Does the palm have large fruits or fronds that need to be removed regularly to reduce the possibility of injury?
Asking and answering these and other questions before selecting a tree will help you choose the "right tree for the right place."
Most palms are grown in containers at nurseries, although larger specimens may be field stock. Choose a healthy palm for the best results in your landscape.
A high quality palm has:A root ball extending from about 8 inches to 2 feet (0.2 to 0.6 meters) beyond the trunk for palms less than 16 feet (5 meters) tall, depending on the species.
A trunk free of mechanical wounds and/or wounds from incorrect pruning.
A full crown of healthy, vigorous fronds (with the exception of Sabal palms in Florida, for which all the fronds are removed).
Uniform trunk diameter
A low-quality palm has:Trunk selections of varying diameter ("hour-glass") or small diameter below the terminal bud ("penciling").
A trunk with wounds from mechanical impacts or incorrect pruning.
Few fronds, poor color for the species, or pest infestation.
Protect the terminal bud to avoid damaging or killing the palm. This is especially important when transporting the palm because excessive vibration may crack the bud. Containerized palms should have their fronds tied together during transport and installation. Dead or dying fronds should be removed prior to transport. If field stock palms need to be pruned, fronds that stand 45 degrees or more over the horizontal plane should not be removed. Fronds should be tied during transport.
The planting hole for a palm should be large enough to allow room for backfilling soil around the root ball. For field stock palms, this is typically about 18 inches (46 centimeters) wider than the root ball on the sides. Plant the palm at the same depth as it was originally grown. Locate the top of the root initiation zone about even with the soil surface. The original depth may have been too deep in the nursery. Planting too deeply may lead to manganese or iron deficiencies, and planting too high may cause the palm to blow over and expose the root initiation zone to air.
Backfill the planting hole with the original soil where possible. Sand or loamy sand soils are best for providing aeration for the roots and adequate drainage. Containerized palms and palms planted in sandy soils generally do not require staking unless the area is prone to hurricane force winds, such as Florida. Field stock palms may be planted with a tree spade. When tree spades are used, vertical trenching, or trenching out from the newly planted palm in a spoke pattern, can be useful to loosen native soils and allow better root penetration.
Palm nutritional requirements vary considerably from other plants, particularly turf. Specially formulated palm fertilizers are available that can help prevent nutritional deficiencies. Improper fertilization can lead to problems such as magnesium deficiency (yellowing fronds), iron deficiency (yellowing young fronds, green mature fronds), manganese deficiency, particularly in alkaline soils (yellowed, frizzled young fronds), and zinc deficiency (small fronds). If a nutrient deficiency is suspected, a plant tissue and soil analysis may be warranted to identify the problem. Your consulting arborist, master gardener, agronomist, or university extension service may be able to recommend testing laboratories and help you interpret the results.
Organic mulches are beneficial to palms as they are to trees. Apply 2 to 4 inches (5 to 10 centimeters) of organic mulch around a palm at a distance of 2 to 4 feet (0.6 to 1.2 meters). Keep mulch away from the trunk. In addition to providing important nutrients, mulch can reduce the likelihood of damage from string trimmers or lawn mowers.
Diseases and Pests
Palms are susceptible to infections by viruses, bacteria, and fungi, as well as to infestation by insects and other pests. Infectious agents and pests vary widely by region and country. A university extension service, consulting arborist, or Plant Health Care specialist familiar with palms in your area may be able to provide a diagnosis and suggestions for treatment.
Most pruning on palms is done to remove dead or dying fronds and/or fruiting clusters, particularly when such parts are large enough to represent a potential hazard to the public, such as coconuts on a crowded beach. Pruning is usually conducted on an annual basis when warranted.
Coconuts may be pruned as often as every three to six months in tropical climates, such as Hawaii. The terminal bud should never be cut or removed because doing so will kill the palm. Avoid removing green fronds (see figure below). Climbing spikes should generally not be used to climb palms for pruning since they wound the palm trunk.
Consider treating nutrient deficiencies along with pruning. Pruning nutrient deficient palms could cause symptoms to appear in remaining foliage. Remove lower fronds that are chlorotic or dead. There is no biological reason to remove live green fronds on palms. Removing live green fronds is not known to reduce future pruning requirements.
Remove lower fronds that are dead or more than about half chlorotic. It is best for the palm if green fronds remain intact. (If you decide to remove green fronds, avoid removing those above a horizontal line drawn across the base of the crown.)
Overpruned palms may have slower growth and may attract pests. They are also more likely to have terminal buds nicked during pruning or to have terminal buds break from winds after pruning, either of which may kill the palm.
Protect Plants from Damage
Maintenance of other landscape components can damage palms. In particular, string trimmers can cut into the root initiation zone, impairing the palm's ability to absorb water and minerals and, in severe cases, affecting the palm's stability.
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UPDATED JULY 2005
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