WASHINGTONIA: CHARACTERISTICS, HABITAT, REPRESENTATIVE SPECIES - BIOLOGY - 2024

Washingtonia is a genus of palm-like plants in the Arecaceae family. They are commonly known as washingtonias, and specifically as the California palm and the Mexican palm. The genus name is in honor of the first president of the United States George Washington.

These are palm trees that are about 25 m tall, palmate-coast leaves that remain attached to the trunk as they age, and form a kind of skirt around it. They have long petioles, and the margin of the leaves is made up of prickly teeth.

Washingtonia filifera. Source: pixabay.com

The inflorescences are panicle-shaped, formed in the middle of the leaves and hang from them. The fruit is a drupe with a blackish appearance, ellipsoidal shape, smooth exocarp, thin and fleshy mesocarp and thin endocarp.

This genus contains two species: Washingtonia filifera and Washingtonia robusta, which basically differ by the diameter of their trunks.

In their natural state or if they are grown together, these palms can be quickly identified from each other, but trying to identify them from herbarium samples is not so easy. One of the reliable ways to distinguish them is through the analysis of their flavonoids.

Both species are mainly used as ornamentals for gardens and are used in the design of landscapes in large cities. They resist drought, salinity, cold and must be directly exposed to the sun.

characteristics

Appearance

These are palm-type plants with solitary or single stems, erect, tall, with a diameter of 100 to 150 cm that are covered with old leaves and marcescent leaves, which form a kind of lack around the stem.

Washingtonia species have a kind of skirt around the trunk formed by the marcescent leaves. Source: pixabay.com

Leaves

When the leaves dry, they reveal the fibers of their veins. The leaves have a very long and divided petiole at their base. Its entire margin has teeth or serrations throughout. They have a greenish-yellowish central nerve. Blades called costa-webmate.

They have an adaxial hastula with an irregular shape, and they do not have abaxial hastula. With fibrous margin and prominent sides. The shape is lanceolate and connate at its base, with cleft apices.

flowers

These plants have axillary inflorescences inside the leaves, they are panicle-shaped, and they arch when they leave the leaves. They have leathery bracts, tubular at the base, flattened distally, a long rachis and no trichomes. Pollination occurs thanks to insects.

The flowers are bisexual and form individually along the rachilla. They have a short pedicel, a serial perianth, a trilobed cupulate calyx, lobed apices, and irregular margins.

They have three long petals, connate at their base, tubular stamens slightly attached to the pistils, devoid of pubescence, connate, thin, long styles and inconspicuous stigma.

Fruit

The fruit of the washingtonias is a drupe with a blackish appearance, ellipsoidal shape, smooth exocarp, thin and fleshy mesocarp, and thin endocarp.

Seeds

The seeds are ellipsoidal, develop a homogeneous endosperm, their embryo is basal and lanceolate.

Landscape with Washingtonia sp. Source: Alexey Komarov

Taxonomy

The genus Washingtonia is composed of two species:

Petioles of washingtonia have spiny teeth all over their margin. Source: pixabay.com

Habitat and distribution

In general, according to the two species of this genus, the washingtonias are distributed in Arizona, Bolivia, California, Cyprus, Florida, Hawaii, Italy, Mexico, Nevada, Spain, the Canary Islands, New Zealand and Algeria.

They live in dry or semi-desert regions, and form a kind of oasis in places near the water. Both species are resistant to cold and droughts.

W. filifera is a species that must be kept in direct sun exposure, it resists cold down to -10 ° C, as well as salinity. When found in soils with high clay content and that retain moisture, it can be affected by Phytophthora.

W. robusta is also a species that must be fully exposed to the sun, but it resists cold down to -5 ° C. Likewise, it tolerates salinity and drought. It grows best in fertile, well-drained soils. However, it can be adapted to any type of soil.

Young plant of Washingtonia sp. Source: Forest & Kim Starr

Representative species

Washingtonia filifera

It is commonly known as California washingtonia or frayed washingtonia. It is a palm with a robust bearing, an upright trunk about 25 m high and up to 1.5 m in diameter. The color of its bark is gray or brown, it has very large palmate leaves with a petiole that measures up to 2 m.

The margin of the leaves has prickly teeth, the leaf blade is 1 to 2 m wide, it is split into many narrow segments that fray at the edges and often have a drooping and flaccid apex.

The inflorescences of this species are formed in the middle of the leaves, they are long and can measure up to 5 m, they hang from the palm tree, they are branchy, with white flowers. The fruits are ovoid, spheroidal or ellipsoidal in shape and measure about 5 or 10 mm.

This species is native to the southwestern United States (California and Arizona) and the northeastern part of Mexico.

Robust Washingtonia

Known as Mexican washingtonia, southern washingtonia, or robusta washingtonia. Contrary to its “robust” name, it is a tall and slender plant, with a subtle trunk that is about 25 m high and about 50 cm in diameter (less than 80 cm) in its middle part.

The leaf blade of this species can reach up to 1 m wide. It has inflorescences that measure up to 3 m and bear pink flowers.

It is a species native to northwestern Mexico, southern Sonora, and Baja California. In Spain it is widely cultivated from Catalonia to Andalusia, in the east and south of the peninsula.

Applications

The washingtonias are used as ornamentals for gardens and cities. Source: pixabay.com

W. filifera is used mainly as an ornamental in gardens and its fruits are edible.

For its part, W. robusta is also cultivated as an ornamental plant. In addition, both its flowers, fruits and buds are used as food; while, its wood is used to make kitchen or household utensils.

Both palms are used in landscape projects in large cities in the United States and Mexico.

References

1. Flora of North America. 2000. Washingtonia Aracaceae. Flora of North America Editorial Committee. Oxford University. United States of America. Pages 105-106. Taken from: books.google.co.ve
2. López González, G. 2004. Palmae Washingtonia. In: Guide to the trees and shrubs of the Iberian Peninsula and the Balearic Islands. 2nd ed. Editions Mundi-Prensa. Spain. Page 155, 225. Taken from: books.google.co.ve
3. Flora of North America. 2019. Washingtonia H. Wendland, Bot. Zeitung (Berlin). Taken from: efloras.org
4. Catalog of Life: Annual Checklist 2019. Genus Washingtonia. Taken from: catalogueoflife.org
5. Laguna Lumbreras, E. Roselló Gimeno, R., Guillot Ortiz, D. 2014. New quotes from representatives of the genus Washingtonia H. Wendl. (Palmae) as non-native in the Valencian Community, and historical aspects about its presence in cultivation in Spain and Europe. Bouteloua 18: 116-130.
6. CONABIO. 2019. Fan palm, Mexican palm. Taken from: biodiversity.gob.mx
7. Infoagro. 2019. The cultivation of the palm tree. Taken from: infoagro.com