Palm trees (Arecaceae) are tropical to sub-tropical plants that come in a wide range of shapes and sizes. They have a few anatomical characteristics in common, one of the chief of which are the leaves. The foliage is called the palm tree frond. Most palms grow fronds from the crown (or top) of the plant. The fronds are one major identifying device, second only to the type of trunk the plant grows. Despite there being over 3,000 palm species, including many that grow fruit, palm leaves come in only four main types or structures: pinnate, palmate, bipinnate and entire.
Palm fronds are the foliage on palm trees, and they come in a wide range of shapes and sizes. Despite the differences, palm fronds fall in four main types or categories, which describe the general structure of the leaves.
How Palm Tree Fronds Grow
Fronds can take three to five years to mature. A 2-1 ratio of juvenile to mature fronds ensures that there is a constant supply available to provide food to the tree. The bud area of the crown holds the developing fronds. As an old frond dies, a new one emerges.
The new fronds emerge from the top of the crown, so the mature older fronds are always those held at the bottom of the foliage like a skirt. Some palm trees are "self-cleaning," and the old fronds fall off, separating cleanly from the palm tree. Others require pruning with sharp, sanitized pruning tools to remove old growth.
Emerged Growth Habit
The way the fronds position themselves after they have emerged indicates the species of the palm. Some fronds hold themselves in clusters or tufts off the trunk. A very few palms actually branch out from the base, and fronds form there.
Most fronds are arching and singular or aerial-branching. The fronds on these are arranged in regular intervals along the stem. When they fall off, they leave characteristic scars on the trunk.
Appearance of a Frond
Palm tree fronds emerge folded up and comprise an area called the cabbage. In some smaller palm species, this part is an edible delicacy. After the young leaf unfurls, it presents with a thick stem that is notched or serrated, then the sheath and the petiole appear. Any of these areas can also bear spines.
Some fronds are only inches long, while other are many feet across. The color of a frond depends on the species, but most are a waxy green with a gray or brownish-green tone on the underside. The fronds can be matte or shiny, thick or thin in composition. The petiole graduates to the separated ends of the foliage, which spread out in a fan shape.
Types of Palm Tree Fronds
Pinnate leaves are the most common form of frond. The foliage resembles a feather and is divided at the end into individual leaflets. There is a thick, central rib in pinnate leaves, and the leaves emerge along it. In contrast, palmate leaves show up on the fan palms. The leaf parts, divided into segments, are set in a circle and come from a central area, radiating outward.
Bipinnate fronds are unusual and resemble a fish tail. They have a similar structure to feather palm leaves, but they're divided into two sections. Another rare structure is an entire leaf, which looks like a pinnate leaf but doesn't divide at the ends into individual leaf sections. Only five palms have entire leaves.
Bonnie Grant began writing professionally in 1990. She has been published on various websites, specializing in garden-related instructional articles. Grant recently earned a Bachelor of Arts in business management with a hospitality focus from South Seattle Community College.