PALM TREE CARE
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."
- Purchasing Palms
- 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.
- Uniform trunk diameter.
- Planting Palms
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. 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).
Palms produce a leaf at a time, and once a full crown of leaves is achieved in a mature individual (for some palms this is just 4-5 leaves, while in other species, this can be over 120 leaves), every new leaf formed is followed by an old leaf dying. This number, unique to each palm, is the ideal number of leaves for that palm to have to grow optimally. Any less leaves than that number and the palm will grow sub-optimally, or slower. Sub-optimal numbers of fronds can weaken a palm, too, and make it more vulnerable to wind damage, parasites and fatal infections. For some reason there is a myth going about that pruning palms will speed up their growth rate. This is actually the opposite of what happens and I have no idea why this myth persists. In an ideal world, we would ONLY prune the dead or broken leaves off each palm.
Green palm leaves, or fronds, are the palms sole source of food (from photosynthesis). Fertilizer is NOT food, but a source of micronutrients the palm uses, along with water and sunlight to make its food. When green leaves are removed, the palm cannot make the ideal amount of food it needs to survive. Fortunately most palms are quite tolerant of this ‘abuse' and can deal with sub-optimal amounts of green leaves... up to a point. So there should be good reasons to prune palms ‘prematurely' as well as pruning in general.
Most palms are pruned to remove dead leaves that can be a source of hiding places for pests.