Nothing like loads of white sunshine, soft sand beneath your feet, a cool drink in hand while you sway in the shade of a palm tree. But what gives the palm leaves their lusciousness and glamour?
The Arecaceae are a botanical family of perennial climbers, shrubs, acaules and trees commonly known as palm trees (owing to historical usage, the family is alternatively called Palmae). They are flowering plants, a family in the monocot order Arecales. Currently 181 genera with around 2600 species are known, most of them restricted to tropical, subtropical, and warm temperate climates. Most palms are distinguished by their large, compound, evergreen leaves arranged at the top of an unbranched stem. However, palms exhibit an enormous diversity in physical characteristics and inhabit nearly every type of habitat within their range, from rainforests to deserts.
Palms are among the best known and most extensively cultivated plant families. They have been important to humans throughout much of history. Many common products and foods are derived from palms, and palms are also widely used in landscaping, making them one of the most economically important plants. In many historical cultures, palms were symbols for such ideas as victory, peace, and fertility. For inhabitants of cooler climates today, palms symbolize the tropics and vacations.
Whether as shrubs, trees, or vines, palms have two methods of growth: solitary or clustered. The common representation is that of a solitary shoot ending in a crown of leaves. This monopodial character may be exhibited by prostrate, trunkless, and trunk-forming members. Some common palms restricted to solitary growth include Washingtonia and Roystonea. Palms may instead grow in sparse though dense clusters. The trunk develops an axillary bud at a leaf node, usually near the base, from which a new shoot emerges. The new shoot, in turn, produces an axillary bud and a clustering habit results.
Exclusively sympodial genera include many of the rattans, Guihaia, and Rhapis.
Several palm genera have both solitary and clustering members. Palms which are usually solitary may grow in clusters, and vice versa. These aberrations suggest the habit operates on a single gene.
Palms have large, evergreen leaves that are either palmately (‘fan-leaved’) or pinnately (‘feather-leaved’) compound and spirally arranged at the top of the stem. The leaves have a tubular sheath at the base that usually splits open on one side at maturity. The inflorescence is a spadix or spike surrounded by one or more bracts or spathes that become woody at maturity. The flowers are generally small and white, radially symmetric, and can be either uni- or bisexual. The sepals and petals usually number three each, and may be distinct or joined at the base. The stamens generally number six, with filaments that may be separate, attached to each other, or attached to the pistil at the base. The fruit is usually a single-seeded drupe (sometimes berry-like) but some genera (e.g. Salacca) may contain two or more seeds in each fruit.
The Arecaceae are notable among monocots for their height and for the size of their seeds, leaves, and inflorescences. Ceroxylon quindiuense, Colombia’s national tree, is the tallest monocot in the world, reaching up to 60 m tall. The coco de mer (Lodoicea maldivica) has the largest seeds of any plant, 40–50 cm in diameter and weighing 15–30 kg each. Raffia palms (Raphia spp.) have the largest leaves of any plant, up to 25 m long and 3 m wide. The Corypha species have the largest inflorescence of any plant, up to 7.5 m tall and containing millions of small flowers. Calamus stems can reach 200 m in length.