PALM TREES: CHARACTERISTICS, HABITAT, PROPERTIES, CULTIVATION, SPECIES - BIOLOGY

The palms (Arecaceae) are a taxonomic family of monocots, the only branch of the Arecales order. Most have arboreal growth with a single, erect stem, crowned by large terminal leaves, generally palmate or pinnate.

Its flowers are arranged in terminal inflorescences with the same number of sepals and petals, provided with one or more spathes; the fruit is a fleshy berry or drupe. They are distributed throughout warm habitats in temperate and tropical climate regions.

Arecaceae. Source: pixabay.com

Despite its great morphological variety, it constitutes one of the most easily recognizable plant families. Indeed, arecaceae include shrub plants of a few centimeters, up to large arboreal palm trees of more than 40-50 m in height.

This group includes approximately 200 genera and about 2,450 species, with a pantropical distribution around both hemispheres. In addition to being a family of great ecological diversity, the majority have great economic utility for the communities where they settle.

General characteristics

Appearance

Palm trees are evergreen arboreal or shrubby plants, with a single or branched stem from the base, of different size, called a stipe. With a smooth, rough, spiny surface or covered with plant remains, it grows vertically or horizontally, being underground or imperceptible in some species.

The stem lacks secondary growth and only has a terminal bud that favors the growth of the stipe and the development of the leaves in a helical manner. The sap circulates through small filamentous ducts located inside the trunks, providing softness and flexibility to the stipe.

Estate

The root system is fibrous or fasciculate, with abundant ramifications that are born from a bulb located at the base of the stipe. The roots, in addition to mechanical support, fulfill the function of nutrition and maintain symbiotic relationships with various soil microorganisms.

Leaves

The typical palm leaves are large, spiral, and alternately growing arranged on a long rachis sheathed around the stem. The leaf surface or blade is webbed, pinnate or bipinnate, with multiple segmented leaflets, generally spindle-shaped and acute.

Palm leaves. Source: pixabay.com

flowers

Palm trees are hermaphroditic, polygamous, dioecious or monoecious plants, with paniculate inflorescences that emerge at the base of the leaf axils or below them. The radial and sessile flowers appear solitary or grouped, with the same number of sepals and welded or free petals.

Each male flower is made up of an evident androecium with 3, 6, 9 or more stamens, the female ones are made up of the gynoecium. The ovaries are superabundant with axillary placentation, and in some species nectaries are located in the septa of the ovary and are characterized by monosulcate pollen.

Fruit

The fruits, usually of a single seed, are highly variable, from dry drupes to fleshy berries, covered by fibers, scales or thorns. The epidermis is usually hard or dry, and the endosperm is fleshy and high in fat and carbohydrates.

Taxonomy

- Kingdom: Plantae

- Division: Angiospermae

- Class: Monocotyledoneae

- Subclass: Commelinidae

- Order: Arecales

- Family: Arecaceae Schultz Sch. (Palmaenom. Cons.)

- Subfamilies: Borassoideae, Ceroxyloideae, Coryphoideae, Lepidocaryoideae, Nipoideae and Phytelephasieae.

Palm flowers Calamus thwaitesii. Source: Dinesh Valke from Thane, India

Habitat and distribution

Palm trees have a pantropical distribution throughout the tropics and subtropics around the globe. They are located in environments with high humidity, average annual rainfall 2,400 mm, rains for more than 160 days and a temperature above 21 ºC.

Most of the species have their origin in the tropical regions of America, Africa and Asia, specifically in Malaysia. In addition, its great ecological diversity includes desert environments, tropical forests, mangroves and temperate zones, from sea level to high mountains.

In the tropics, palm trees grow in the most diverse climates, being more frequent in the humid tropical forests. In the Andean region and over 1,000 meters above sea level there are more than 35 genera and about 120 species.

Properties

Arecaceae constitute one of the botanical families of great application and economic importance, whether in construction, traditional medicine or as food. Certain fruits are edible or are used as animal food, the logs are used in construction and even for the manufacture of canoes.

At an industrial level, it is a raw material for obtaining oils and fibers, as well as for the production of alcoholic beverages and honey. On the other hand, it is used in traditional medicine as an anti-inflammatory and to regulate blood pressure and glycemia in the blood.

Palm fruits. Source: pixabay.com

Culture

Reproduction

Most of the species belonging to the Arecaceae family multiply by seeds, although some propagate vegetatively. For example, the Caryota mitis species multiplies by division of strains or separation of suckers from the trunk of the plant.

Sowing should be done immediately after harvesting the clusters with the ripe berries, when they change from green to red. Due to its hard consistency, it is best to hydrate the seeds for 2-12 days prior to sowing.

For some fleshy species, it is convenient to extract the pulp and change the water daily to prevent the seeds from rotting. In other cases, they can be wrapped and moistened in moss, sowing immediately on fertile substrate and constant humidity.

The seeds must be fresh and ripe, since storage tends to decrease their viability and germination percentage. It is generally advisable to use seeds with only 4-8 weeks of maturation and harvesting.

The substrate must be fertile, loose and with good moisture retention, at least a mixture of peat and sand in equal parts. Sowing is done in polyethylene bags, placing the plantation in a humid, warm (25-30 ºC) and aerated environment.

The disinfection of the seeds and the substrate is essential to avoid the appearance of phytopathogenic fungi or the appearance of insect larvae. Likewise, the cleaning and elimination of the bark of the fruits favors the rapid germination of the seeds.

Preserving the right conditions, the seeds take from 1-6 months to 2 years to germinate, also depending on the species and type of seed. At the nursery level, the use of gibberellic acid at a dose of 500-1,000 ppm increases the germination percentage.

Salacca magnifica palm stem. Source: RuB (Ruddy Bénézet)

Requirements

Palm trees are adapted to various types of soils, but regularly prefer loose, well-draining soils. As well as soils with a high content of organic matter and a neutral-slightly acid pH, or poor, sandy soils with low moisture retention.

In general, palm trees thrive in environmental conditions where the temperature does not exceed 25 ºC, and the thermal ranges are minimal. Low temperature being one of the most limiting factors when selecting the place to establish the plantation.

Indeed, the cold reduces the functioning of the root system, the transport of nutrients and growth, weakening the plant in general. The palm trees become more sensitive to the attack of pests and diseases, reduction of the diameter of the stipe and defoliation occurs.

On the other hand, despite the fact that the palm trees resist strong winds, they must be located in protected areas. Many species withstand even hurricanes, losing only the foliage, but others are sensitive to dehydration caused by drafts.

In addition, the proximity to the sea causes the winds to deposit small particles of salt on their leaves that burn and damage their leaves. For this reason, species with thick and waxy leaves have a greater adaptability to marine conditions.

As for solar radiation, its location in clear places that provide a greater number of light hours favors its growth and development. Tropical palms planted in pots require frequent watering, 25,000-40,000 lux and temperatures above 12-15ºC.

Care

Sowing should be done from spring to mid-summer, trying to eliminate the dry roots and burying down to the level of the leaves. The planting hole should be large enough so that the roots have room to expand.

It is recommended to add some amount of compost and sand to the planting hole to improve drainage and moisture retention. In slow-draining soils, planting is done slightly elevated to avoid root rot.

In very dry soils it is recommended to place a layer of dry leaves or "mulch" around the plant to maintain humidity. Even this practice allows to maintain humidity and provide nutrients when the plant material decomposes.

Many palm species are drought tolerant, however they require good moisture availability during their active growth phase. Others, despite not reaching a large size, tend to expand their root system, requiring a greater supply of moisture.

In palm trees, pruning is limited to the separation of dead or diseased leaves, and the removal of the suckers or clusters of fruit. The elimination of the diseased leaves avoid the spread of diseases, and if the proliferation of the suckers is not desired it is convenient to separate them.

Palms. Source: Estorgik

Diseases

False burning or swelling of the leaves (

Symptoms appear as small black bumps covered by small brown spirals that are the conidiophores of the fungus. The infected tissues turn yellowish and the leaves tend to die prematurely. Control requires the removal and burning of affected plants.

Leaf spots (

The disease initially manifests itself as small, round, greasy or transparent patches of a yellowish color. Later they turn brown with a yellow halo, grow, join and take an irregular gray-brownish color.

Mottled and rotten heart (

The mottling of the leaves appears as the desiccation and yellowing of the leaves whose petioles are infected. The terminal bud or heart of the palm tree tends to blacken, rot and die. The highest incidence occurs in hot and humid environments.

Bud rot (

The symptoms of the disease are manifested as the rotting of the new tissues, preserving the leaves formed before the infection. The highest incidence occurs on the terminal meristematic tissue of the plant, in severe attacks it is capable of causing death.

Representative species

Areca vestiaria

Palm tree with the highest distribution globally in lower forest extracts, from the Philippines, India, Indonesia and Malaysia, to southern China. They have single or multiple stems that reach up to 5 m in height, pinnate leaves and it is used as an ornamental.

Areca dress. Source: Pescov

Bismarckia nobilis

Decorative palm tree 12 m high with a single, robust and straight stem, native to Madagascar, it is the only species of its kind. Green-bluish foliage, pointed leaves reach 3 m in diameter, interfoliar inflorescences and black fruits when ripe.

Bismarckia nobilis. Source: Mmcknight4

Cocos nucifera

It is one of the most popular species around the world. Although its origin is uncertain, it multiplies spontaneously on the Brazilian coast. The stipe reaches up to 20 m in height, foliage formed by deep green sheets and its edible fruit is the coconut.

Cocos nucifera. Source: Forest & Kim Starr

Phoenix canariensis

Palm formed by a solitary stipe 20 m high, robust and elevated, native to the Canary Islands. It has compact pinnate foliage with numerous rigid dark green leaflets, orange branched inflorescences and fruit in clusters of golden tones.

Phoenix canariensis. Source: User: Nikater

Roystonea regal

15 m tall plant with a whitish stipe at the base, native to Cuba, Guyana and Panama. The pinnate leaves have large scattered leaflets, subfoliar inflorescences and small round purplish fruits.

Roystonea regal. Source: Karelj

Trachycarpus fortunei

Palm of medium size that reaches 12 m in height with the stipe covered with a layer of dark fiber, native to China. Fan-shaped foliage with rigid leaves forming a dense crown, interleaved and branched inflorescences, bright blue reniform fruits.

Trachycarpus fortunei. Source: C. Löser

Washingtonia filifera

Native to North America, it has a robust and solitary stipe up to 15 m high with abundant remnants of superficial foliage. Foliage arranged in a fan with segmented and hanging leaves, long spiny petioles, interfoliar and hanging inflorescences, small black fruits when ripe.

Washingtonia filifera. Source: Staplegunther at English Wikipedia

References

Arecaceae (2018) CEAP Design. Centro de Estudos Ambientais e Paisagisticos Botanical research and professional practice Retrieved at: ceapdesign.com.br
Arecaceae Bercht. & J. Presl (2017) Vascular Plant Systematics Laboratory. Recovered at: thecompositaehut.com
Bernal, R., & Galeano, G. (2013). Harvest without destroying. Sustainable Use of Colombian Palms. Bogotá: Faculty of Sciences, Institute of Natural Sciences, National University of Colombia.
Borchsenius, F., & Moraes, M. (2006). Diversity and uses of Andean palm trees (Arecaceae). Economic Botany of the Central Andes, 412-433.
Cabral, E., Casco, S., & Medina, W. (2016). Plant diversity consultation guide. Facena (UNNE). Monocots - Arecales: Arecaceae.
Espinoza Flores, Y. (2008). Current status of the collection of palms (Arecaceae) of the National Herbarium of Venezuela (VEN). Peruvian Journal of Biology, 15, 97-102.
Plumed, J., & Costa, M. (2013). The palms: botanical monographs. Universitat de València Sánchez de Lorenzo Cáceres, JM (2014) Family Arecaceae (Palmaceae). Ornamental Flora of Spain. Recovered in: arbolesornamentales.es

PALM TREES: CHARACTERISTICS, HABITAT, PROPERTIES, CULTIVATION, SPECIES - BIOLOGY - 2024