Planting palms

For successful, rapid establishment of palms you need to follow just a few, simple rules. Commercial operators with the right equipment routinely move mature palms to landscape sites, making palm trees a valuable landscape-design option. Because palms lack a woody tap root and naturally initiate new roots from the trunk base or cut roots, palm specimens of almost any size are relatively easy to plant and transplant.

Transplant size Containerized palms experience little or no root disturbance, so the only factors limiting their size are your ability to handle heavy, bulky specimens safely and the equipment you need to do it. When transplanting palms from one site to another or digging field-grown plants in a nursery, it is important to select specimens with some visible trunk. These will be relatively tolerant of root disturbance and will re-establish more quickly. For species that have early underground stem development such as Sabal (palmetto palm), Bismarckia (Bismarck palm), Latania (Latan palms), Rhopalostylis (shaving-brush palms) and some Livistona species (fountain palms), it is especially important to limit transplanting to specimens with visible, above-ground stem.

Planting time Transplanting is most successful in the warmer months-from late spring until fall-when roots are most active. However, in South Florida-where soil is nearly always warm-planting containerized palms and transplanting are possible year round. Further, in regions where the warmest months correspond with the rainy season, higher humidity reduces the need for supplemental irrigation.

Root-ball size When transplanting most palms, a good rule of thumb is for the root ball to extend at least a shovel's width out from the trunk. For multi-stemmed and large specimens such as Phoenix reclinata (Senegal date palm), Chamaerops humilis (Mediterranean fan palm), Washingtonia robusta (Mexican fan palm) and Roystonea regia (royal palm), the root ball should extend at least 2 feet out from the trunk. Generally, a larger root ball ensures a more successful and rapid re-establishment. However, you must balance this with the fact that palms with large root balls are more difficult and expensive to move due to their size and weight. Also, you must fill the hole left after you dig a palm with a large root ball. This requires more labor and expense, and perhaps even additional soil.

Landscapers usually do not root-prune palms before transplanting except for particularly valuable specimens of species known to have little or no root resprouting. If you choose to root-prune, do so 2 to 3 months before digging to allow sufficient time for new roots to initiate from the trunk base.

Leaf removal Ideally, it would be best to remove all leaves when transplanting palms to reduce water loss from transpiration. Although aesthetic considerations usually discourage this practice, you should remove all leaves from species that regenerate a new root system from the trunk base, such as Sabal palmetto. For species that resprout from cut roots, remove as much foliage as aesthetics will allow. At a minimum, remove the lower half of the crown and tie up the remaining leaves in the upper half of the crown with untreated, 4-ply, biodegradable twine. The twine will deteriorate naturally in several months to let the fronds unfold. Some authorities-though not all-feel it is best to remove the ring of leaves next to the apical bud to prevent excessive pressure on the bud from the tied leaves. Leaf removal is unnecessary when planting containerized palms.

Transport You must provide good support and protection of palm specimens during moving and handling to prevent injury to the bud and trunk. Each palm trunk usually has only one growing bud and severely injuring it may result in the death of the palm. Further, because palm bark has no cambium, wounds are permanent eyesores as well as potential entry sites for diseases and insect pests. Some species, such as Archontophoenix cunninghamiana (king palm), are unusually sensitive to rough handling. You should provide this-and other slender-trunked palms with heavy crowns-with a sturdy wooden splint securely attached along the trunk and extending into the leaves (see illustration below). This will prevent the weight of the crown from snapping the apical bud. Tie stems of the multi-trunked species together for additional protection.

To prevent injury to the trunk, use nylon or burlap slings and ties to support and grasp palms when moving and handling them with heavy equipment. Place palms securely on the vehicle, either standing them up at an angle away from the wind or laying them down with the root balls forward. Cover the root balls and crowns with shade cloth or a similar protective material during transport to prevent wind and sun damage, and excessive drying.

Site preparation Plant uncontainerized palms immediately. If this is not possible, shade the root ball, trunk and crown, and keep them moist until planting. You can temporarily heel in the root ball in moist mulch to hold a palm until you plant it.

Palms are particularly sensitive to poor drainage and excessively deep planting. Therefore, you should make the hole the depth of the root ball and about 6 inches wider. If the soil drains slowly or if the site has a high water table, provide subsurface drainage to carry away excess water. If you cannot do this, you must ensure that the root ball will remain above the water level after planting.

Planting Position the root ball in the planting hole so the palm's most attractive side addresses the main viewing perspective. Backfill with the same un-amended soil you excavated from the hole, being sure to thoroughly tamp out air pockets. If a customer demands that you incorporate soil amendment, use no more than 25 percent by volume.

Large palms may require support for stabilization until they become well established (see illustration, below left). Use 2 x 4 or 4 x 4 wooden bracing attached to 1-foot lengths of 2 x 4 vertically strapped or banded around the trunk. Protect the trunk with a wrap of nylon, burlap or another cushioning material where you have secured the 1-foot lengths of 2 x 4s. Do not nail into the trunk-nailing causes permanent wounds. You also can secure palms with guy wires or cable instead of wooden bracing. Do not attempt to stabilize palms by planting them deeper in the ground. Although some palms survive deep planting, most do not.

Construct an irrigation berm 4 to 6 inches high around the root ball and hole. Apply a 3- to 4-inch layer of mulch around the base of the palm to encourage new root growth and suppress weeds. Irrigate thoroughly at planting.

Post-planting care Irrigation is probably the most critical factor affecting post-planting survival. Keep the root ball and soil evenly moist but not saturated. Do not allow turfgrass or weeds to encroach upon the trunk base. A fungicidal soil drench for root disease 2 to 4 times during the first few months may be beneficial as a preventive measure. Apply a slow-release fertilizer to the soil surface around the outside margins of the root ball 3 months after planting. Specialized palm fertilizer is available for this, with ratios of 3-1-3 or 3-1-2 plus magnesium and micronutrients. Periodic micronutrient foliar sprays for valuable or stressed specimens also may be wise until establishment is complete. Begin a regular fertilization program once the palm is fully established and growing vigorously, following directions provided by the palm-fertilizer manufacturer. For particularly valuable specimens, especially those that must regenerate a new root system from the trunk base, provide intermittent mist and artificial shade to help speed establishment.

As you can see, transplanting palms is not complicated. Containerized palms are even simpler to work with. Gentle handling, knowledge of the species and common-sense techniques will result in successful establishment of a vigorous, healthy tree.

Donald R. Hodel is an extension horticulturist at the University of California-Los Angeles.

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