UNITED STATES—Palm trees qualify as trees merely 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 almost a 100 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.
Foliage is their primary attribute.
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 cannot 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 cannot 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.
Highlight: California Fan Palm
California fan palm, Washingtonia filifera, is the only palm that is native to California. It is naturally exclusive to very distinct ecosystems, though. It inhabits isolated riparian oases of the Colorado Desert. Some also inhabit the Mojave Desert and the Sonoran Desert. It prefers arid warmth. Unfortunately, it may not perform as well within milder climates here.
Otherwise, it is a stately palm that is more adaptable than most are to formal landscapes. It resembles Mexican fan palm, but is shorter and stouter, with a fluffier canopy. It tends to stand straighter, with neatly bare gray trunks. Groomed trees rarely retain petiole stubble. Alternatively, they are handsome, although combustible, with full beards of dried leaves.
California fan palm grows about fifty feet tall, and taller in the wild. Its canopy may be 10 to 15 feet wide. If flattened, its fronds, or complete leaves, might be more than 10 feet long. Stiff petioles, with rigid and sharp teeth, are a bit more than half of their total length. The species name filifera describes filaments that hang from the clefts of fronds, and new bud growth.
