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Palm Trees Deserve Special Accommodation

Palm trees are bold landscape features.

Palm trees qualify as trees only because of their size and form. The most familiar sorts here develop trunks, and many grow quite tall. The smallest houseplant palms can grow as tall as dwarf citrus trees. Mexican fan palm can grow nearly a hundred feet tall. Palms are monocots, though, so are not actually woody. Technically, they are herbaceous trees.

Palm trees share this distinction with several other herbaceous trees. Banana tree trunks are just tightly rolled leaves. Tree ferns elevate their growth on roots that grow downward through rotting stem growth. Neither banana trees nor tree ferns can generate branches. Sago palms, cabbage trees and arboriform yuccas develop branches, but without wood.

Some palm trees develop a few trunks, but almost none develop branches above grade. Date palms can, but rarely branch. Doum palms typically branch, but are extremely rare. Any other branching palm trees are either aberrative or not really palm trees. Palm trunks do not grow wider as they grow taller. Adventitious roots can become buttressed, though.

All palm trees are evergreen, with either pinnate or palmate foliage. Feather palms have pinnate foliage. Each leaf consists of a central rachis that supports many narrow leaflets. Fan palms have palmate foliage. Each leaf radiates from the terminus of its stout petiole. Both basal leaflets of feather palms and petioles of fan palms are typically horridly spiny.

Since palm trees can not branch, they are not conducive to pruning to direct their growth. Their big but solitary terminal buds grow only upward and maybe away from shade. Any that reach high voltage cables can not go around, so necessitate removal. Clearance for overhanging obstacles is a major consideration for situating new palms. Some grow fast.

While unconducive to directional pruning, most palm trees benefit from grooming. Only a few shed their old foliage naturally. Most get shabby by retaining it. Many, particularly fan palms, eventually become combustible or infested with rodents. However, some may be visually appealing with neat beards of old foliage. Only arborists can groom large palms.

Posted on by tonytomeo

Dracaena Palm

Modern dracaena palms are more compact, more colorful and more user friendly than old fashioned sort.

(This article was deferred from yesterday morning.)

            While hoping to find some of the uncommon yuccas that I still lack, I instead encountered some of their friendlier kin in a local nursery. Even though dracaena palm, Cordyline australis, is an old fashioned plant that was probably considered to be too common until the past few decades, many more colorful modern cultivars are restoring its appeal. Classic dracaena palm has olive drab foliage. The nearly as traditional bronze dracaena, ‘Atropurpurea’, has reddish bronze foliage. The more contemporary ‘Red Star’ though is deeper purplish red. ‘Pink Stripe’ has bronzy green leaves with pink edges. ‘Sundance’ has pink in the middle with green edges.

            Modern cultivars also stay shorter so that their abundant foliage can be appreciated on a more personal level. The individual sword shaped leaves are about three feet long and three inches wide, a bit larger than traditional dracaena palm leaves. However, I actually prefer the traditional dracaena palms that can get taller than twenty feet and spread nearly half as wide, with sculptural bare trunks and high branches.  

            Any dracaena palm that gets too tall can be cut back to a more proportionate height. One of my colleagues recommends cutting about a quarter through trunks a year or more prior to cutting back, to stimulate new shoot growth just below the cut. The new growth prevents the trunks from being bare immediately after getting cut back. Overgrown heavily branched trees should first be thinned to decrease their weight before cutting partly through their trunks. Young plants can be cut back to the ground to regenerate with multiple trunks.

            Billowy trusses of tiny pale white flowers add interest at the end of spring, particularly against darker foliage. I am told that the flowers of modern cultivars are slightly fragrant. However, against the olive drab foliage of older dracaena palms, I think that the blooms look rather dusty, and do not smell any better.

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Mexican Fan Palm

Palms are familiar within Californian landscapes.

California fan palm is the only palm that is actually native to remote regions of California. However, Mexican fan palm, Washingtonia robusta, is much more common. Technically, its native range is not far away. It had been the most popular of palms prior to the 1990s. It is more adaptable to more populous climates. Also, it naturalizes within some regions.

Mexican fan palms grow vigorously while young. Growth decelerates with maturity. Very old trees can grow very slowly without completely stagnating. Wild specimens may have potential to survive for a few centuries with such slow growth. Cultivation and irrigation of home gardens may limit this potential. Few local specimens are more than a century old.

Mexican fan palms are taller and slimmer than California fan palms. Their trunks lean as prevailing wind blows them. They easily grow fifty feet tall, and eventually get a hundred feet tall. Such tall and leaning trunks can suspend their canopies over adjacent gardens. Their pleated and palmate leaves are about three feet wide, on petioles with nasty teeth.

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Palm Trees Are Specialized Trees

Many palms have palmate leaf form.

A tree is a woody perennial plant with a single tall trunk and branches. Banana trees and tree ferns lack both branches and wood. Arboriform yuccas develop branches but are not woody. Palm trees are no better. Some develop a few trunks but without branches. Doum palms that develop branches are extremely rare in California. No palm is actually woody.

Palms are trees only because of their size and form. In other words, most are big and tall. The most compact of palms are no smaller than Japanese maples, which are also trees. Realistically though, palms are merely large to very large perennials. They are monocots like grass, bamboo or cordyline. Some horticulturists classify them as herbaceous trees.

Only California fan palm is native to California, and only to remote desert oases. All other palms are exotic. Spanish Missionaries imported date palms to produce dates within arid regions. Only a few other palms were similarly utilitarian. The majority are desirable only for their distinctive form, texture and evergreen foliage. They are genuinely ornamentals.

All palms are evergreen. Fan palms produce rounded palmate leaves on sturdy petioles. Feather palms produce elongated pinnately compound leaves on sturdy rachises. Many fan palms also produce wicked teeth on their petioles. Many feather palms also produce dangerously sharp spines on the bases of their rachises. Even lush palms can be mean.

Not many palms get big enough to provide much shade. Many types are shady in groups though. Without branches, palms are not conducive to containment or redirection. Some eventually grow tall enough to shade neighboring gardens instead. Unfortunately, palms that encroach too closely to high voltage cables require removal. They do not go around.

Palm trunks do not widen as their canopies grow higher above. Palms with plump trunks grow at ground level for several years before they can launch. Their single terminal buds must first grow as wide as their mature trunks will ever get. Their foliar canopies likewise grow no broader than they were when they launched. They only grow higher. Most large palms develop distended basal adventitious roots that can get quite wide, though.