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 Roystonea subsp. var.  Royal palm
Habit: palm-cycad
Height: to
Width: to
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Lifespan: perennial
Features: evergreen, foliage
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Arecaceae > Roystonea var. ,

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Roystonea is a genus of 10 species of monoecious palms, native to the Caribbean Islands, and the adjacent coasts of Florida, Central and South America. Commonly known as the royal palms, the genus was named for Roy Stone, a U.S. Army engineer. It contains some of the most recognizable and commonly cultivated palms in tropical and subtropical regions.

Detail of the base of the stem of Roystonea dunlapiana showing columnar stem and leaf scars.

Roystonea is a genus of large, unarmed, single-stemmed palms with pinnate leaves. The large stature and striking appearance of a Roystonea palm makes it a notable aspect of the landscape. The stems, which were compared to stone columns by Louis and Elizabeth Agassiz in 1868, are smooth and columnar, although the trunks of R. altissima and R. maisiana are more slender than those of typical royal palms. Stems often are swollen and bulging along portions of their length, which may reflect years where growing conditions were better or worse than average. Leaf scars are often prominent along the stem, especially in young, rapidly-growing individuals. Stem colour ranges from grey-white to grey-brown except in R. violacea which have violet-brown or mauve stems. The largest royal palm, R. oleracea, reaches heights of 40 m , but most species are in the 15 to 20 m range.[1]

Close up of crown of Roystonea regia showing smooth tapering leaf sheath and fresh leaf scars, Kolkata, India

Roystonea leaves consist of a sheathing leaf base, a petiole, and a rachis. The leaf base forms a distinctive green sheath around the uppermost portion of the trunk. Known as the crownshaft, this sheath extends 1.4 - 2 m down the trunk. The petiole connects the lead base with the rachis. Zona only reported petiole lengths for three of the 10 species, ranging from 20 to 100 cm. The rachis is pinnately divided and ranges from 3.2 to 5.8 m long. The leaf segments themselves range in length from 60 to 79 cm in R. altissima up to as much as 132 cm in R. lenis. They are arranged in two or three planes along the rachis. Many authors have reported that the leaves R. oleracea are arranged in a single plane, but American botanist Scott Zona reported that this is not the case.[1]

These plants have the ability to easily release their leaves in strong winds, a supposed adaption serving to prevent toppling during hurricanes. Inflorescences occur beneath the crownshaft, emerging from a narrow, horn-shaped bract. The flowers on the branched panicles are usually white, unisexual, and contain both sexes. The fruit is an oblong or globose drupe 1-2 cm long and deep purple when ripe.[2] Some species so closely resemble one another that scientific differentiation is by inflorescence detail; flower size, color, etc.

Standard Cyclopedia of Horticulture

Oreodoxa (Greek, mountain glory"). Palmaceae. The royal palm, cabbage palm, and a very few others, from Florida to northern South America, comprising the finest species of palms in cultivation; pinnate- leaved, with tall columnar boles.

The genus Oreodoxa, as formerly understood, has recently been divided, and the Florida and West Indian royal and cabbage palms have been separated as Roystonea and the name Oreodoxa has been reserved for South American species. This separation proceeds on the basis of the botanical distinctness of the two groups and also for nomenclatorial reasons. Oreodoxa was established by Willdenow in 1804 for 2 Venezuelan species, neither of which is congeneric with the VV. Indian royal palms. The type species, O. acuminata, Willd., is associated by some authors with Euterpe, bv others with (Enocarpus. (See O. F. Cook, Science if 12:479 (1900); Bull. Torr. Bot. Club, 28:549 (1901), and 31:349 (1904); also Cook & Collins, Ec. PI. Porto Rico). Nevertheless, this disposition has not been accepted by other palm students, as Beccari, and Dammer & Urban; and until something like an agreement is reached (and without expressing any opinion on the merits of the case), it is better for a cylcopedia of horticulture to hold to a conservative practice. For Beccari's recent treatment, see Pomona College Journ. Econ. Botany, May, 1912. As usually denned, and as understood by Mart-ills (not Willdenow), Oreodoxa comprises spineless palms, the solitary erect robust trunk cylindrical or swollen at the middle: Lvs. terminal, equally pinnatisect; segms. narrowly linear- lanceolate, narrowed at the apex, unequally bifid; midnerve rather thick, scaly beneath; margins not thickened, recurved at the base; rachis convex on the back, sulcate toward the base, and acute toward the apex above; petiole half-cylindrical, sulcate above; sheath long: spadix rather large, with long, slender, pendent branches; spathes 2, the lower broad, laterally carinate, shorter than the spadix, the upper complete semi-cylindrical, ventrally fissured: bracts and bractlets scaly: fls. small, white, in scattered glomerules: fr. obovoid or oblong-ovoid, small, violet; seed small, rounded, depressed, or obovate and somewhat curved, with sub-basal embryo and uniform albumen.

The two well-known Oreodoxas are the royal palm (O. regia) and the cabbage palm (O. oleracea). Both are stately trees. While it is often difficult to distinguish immature specimens of the royal and cabbage palms, in age they are distinct. O. regia has staminate flowers which, in bud, entirely inclose the stamens, while in O. oleracea the stamens protrude before the flower opens. In the latter species, also, the fruit is nearly twice as long as wide, while in O. regia it is not more than a third longer than wide. The character of trunk swelling, usually applied as a distinguishing mark, is likely to break down in some wild plants. The royal palm is one of the grandest of pinnate palms, growing to a height of over 100 feet with immense plumy feathery leaves and a straight white trunk. It is a magnificent tree for extreme southern Florida for avenue planting, and is valuable in all sizes, but especially when 4 feet or over in height. The form of it native in Florida is by some regarded as a distinct species. The cabbage palm is cut down when three years old for the central leaves, which are tender and edible.

In southern California, the royal palm lives for years but without attaining any size, and is therefore not accounted a success there. Because of the original error in assigning the West Indian royal palms to Oreodoxa of Martius, which itself is untenable, the names of these plants and their relatives are badly mixed.

The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.



Pests and diseases




  1. 1.0 1.1 Zona, Scott (December 1996). "Roystonea (Arecaceae: Arecoideae)". Flora Neotropica 71: 1–35. 
  2. Riffle, Robert L. and Craft, Paul (2003) An Encyclopedia of Cultivated Palms. Portland: Timber Press. (Page 441) ISBN 0881925586 / ISBN 978-0881925586

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