About Palms

Palms are one of the most easily recognizable plant groups. Originally named “Principes,” the princes of the plant world, by Linnaeus, palms and their products are an integral part of human culture in warmer regions of the globe. Palms have been used as crop plants for centuries, providing important sources of food and a variety of other products. Few plant groups evoke the diversity of feelings and emotions that palms do – for most of us, palms represent the lure, romance, and relaxation of the tropics.

Taxonomy

About the Resource The palm family (Palmae or Arecaceae) includes approximately six subfamilies, 192 genera, and over 2,800 species, making it one of the largest botanical families (Dransfield et al., 2008). Palms belong to the phylum of angiosperms known as monocotyledons, commonly referred to as monocots. Monocots also include grasses, orchids, bromeliads, and many others. Although palms are often referred to as trees (they are one of only a few monocot families with arborescent species), most trees that we are familiar with, such as oak, elm, and magnolia, belong to the angiosperm division commonly referred to as dicots.

The taxonomic classification of palms used for this resource is as follows:

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Geography

Palms can be found on all continents except Antarctica. The greatest diversity of palms occurs in tropical regions of the world; the majority of species are found in warm, humid, lowland tropical regions. Approximately 75% of the species occur in rainforests, and many of these species are adapted to swamps. A few species can be found in cooler climates at higher elevations within the tropics.

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Economic Importance

Palms are a source of food, oil, rope, fiber, baskets, hats, mats, tannin, thatch, beverages, furniture, and narcotics. Three species of palms are foremost in importance for local economies and for commerce: Cocos nucifera (coconut palm), Elaeis guineenis (African oil palm), and Phoenix dactylifera (date palm). In addition to the many diverse products that can be harvested from a palm, palms are widely used in the landscape throughout the tropics and subtropics and in interiorscapes throughout the world.

In temperate regions of the globe, we bring these plants into our lives by growing them in homes, malls, offices, and other interiorscapes. Commercial palm production for interiorscapes and landscapes has become a large part of the ornamental horticulture industry in Florida, Hawaii, California, and Texas. A number of palm species available at garden centers and nurseries are relatively easy to propagate, fast growing, adaptable to urban landscapes and interiorscapes, and reasonably resistant to pests and diseases.

Field production is the most practical means of producing large palm specimens for the tropical, subtropical, and Mediterranean climates of the world. Container-grown palms are produced for three markets: 1) liners for field production, 2) wholesale or mass-market retail sales for residential landscapes, and 3) interior specimens for houseplants and interiorscape use. The largest market for container production is for interiorscapes.

An Encyclopedia of Cultivated Palms (Riffle and Craft, 2003) is an excellent accounting of palms that may be grown in landscape and in interiorscapes. Over 850 species grown worldwide are discussed in detail, including information on cold hardiness, water needs, height, and special growing requirements.

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Diseases and Disorders of Palms

Palms are unique in their morphology and therefore, not surprisingly, in their cultural requirements (Broschat and Merrow, 2000). They are prone to a variety of diseases and nutritional disorders, some of which can be fatal. Pathogens palms may be susceptible to include viroids, viruses, phytoplasmas, bacteria, algae, fungi, flagellated protozoans, and nematodes (Broschat and Merrow, 2000). Some of these may cause only minor leaf spots while others may lead to the death of the palm.

Broschat and Elliott (2005) provide an excellent pathway key to palm disorders and diseases that is based solely on visible symptoms. Fortunately, symptoms alone are often sufficient to diagnose palm diseases and disorders.

Within the Caribbean and the United States, movement of palms is common and is probably the primary method of palm pathogen movement into new areas (Elliott et al., 2004).

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Arthropod Pests

Relative to most cultivated plants, palms are relatively pest-free. However, a number of arthropod (Phylum Arthropoda) pests attack palms in sufficient force to warrant control measures. Some pests are chiefly a problem in container production, while others cause damage to palms in the landscape, in interiorscapes, and in field nurseries.

Howard et al. (2001) provides an excellent discussion on palm defoliators, sap-feeders, and stem borers, categorized by arthropod order. In the class Insecta, Howard et al. (2001) recognizes six orders known to contain species that are notable pests of palms worldwide: Orthoptera (grasshoppers and crickets), Phasmatodea (walking sticks), Thysanoptera (thrips), Hemiptera (true bugs, hoppers, whiteflies, aphids, and scale insects), Coleoptera (beetles), and Lepidoptera (moths and butterflies). The authors also offer a brief discussion of the other major group of arthropod palm pests, mites (Class Acari).

The taxonomy for the major groups of arthropod palm pests included in this resource is as follows:

Worldwide, two Orthoptera families are important palm pests: Acrididae (short-horned grasshoppers), Tettigoniidae (long-horned grasshoppers). Grasshoppers are not considered major pests of palms in the United States and Caribbean and so are not included in this resource. In the southeastern United States, the lubber grasshopper (Romalaea guttata) sometimes consumes parts of palm leaf blades in nurseries and in the landscape but not usually to a level that it is considered a significant pest (Broschat and Meerow, 2000). Though several species of walking-sticks (Phasmatodea) are considered palm pests in the Pacific islands, they are not considered pests of palms in the United States and Caribbean. Thrips (Thysanoptera) can be found on outdoor palms, but they are more likely to be seen on palms in interiorscapes and nurseries. Palm pests of the order Hemiptera include true bugs (suborder Heteroptera), leafhoppers and planthoppers (suborder Auchenorrhyncha), aphids (family Aphididae), whiteflies (family Aleyrodidae), and mealybugs and scales (superfamily Coccoidea). Beetles considered as palm pests are found in four Coleoptera families: Bostrichidae, Curculionidae, Scarabaeidae, and Chrysomelidae. Two species of mites (Order Acari) are recognized by Howard et al. (2001) to be major pests of cultivated palms worldwide. Spider mites (Tetranychus spp.) are pests on greenhouse and indoor palms. Coconut mites (Aceria guerreonis) feed on the husk of coconut fruits. Moths and butterflies are some of the most destructive pests of palms worldwide (Howard et al., 2001). Many of the species are major pests in palm plantations, in palm landscapes, and in palm nurseries. Lepidoptera palm pests in the United States and Caribbean are represented in the following families: Castniidae, Coleophoridae, Hesperiidae, Limacodidae, Noctuidae, Saturniidae, and Tineidae.

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