Palms belong in their own plant family, Arecaceae, containing some 2,500 different palm species worldwide. Their leaves are generally called fronds. The base of the frond where it attaches to the trunk is called the sheath, and the stem of the frond is the petiole. The blade or segments of leaflets are referred to as lamina. The color of a palm's frond is species-specific: they are either a shade of green, bluish-green or powdery silver. Some fronds emerge pink, coppery or red but later mature a different color.
Relatively few palms produce fronds that are entire, which means having a blade that is not segmented. Paul Craft and Robert Lee Riffle, authors of "An Encyclopedia of Cultivated Palms," do not even use entire as a descriptor. Rather, they use "unsegmented leaves that are palmate" in shape in their comprehensive book. An example of an entire-leaf palm species is the diamond joey palm or the two-lobed leaf of the necklace palm.
Plants with palmate fronds are commonly referred to as fan palms. Each frond has a circular or semi-circular blade with many cut segments to create a zig-zag edge to the frond. The blade also may be held broadly and flat like a plate, or the blade may undulate and fold, which it then is regarded as costapalmate. Costapalmate fronds usually have a midrib and the segments are v-shaped, whereas simple palmate fronds lack these features and look much simpler. An example of a basic palmate leaf is the Chinese fan palm. Bismarck palm and cabbage palm plants produce costapalmate fronds.
Pinnate fronds look like feathers or quills. They have many linear leaflets that angle off the frond's midrib, called the rachis. These leaflets can be arranged in a flat, one-plane manner or radiate out in several directions from the rachis to look very frilly and full. The coconut palm and majesty palm produce one-plane pinnate fronds, while the foxtail palm's fronds' leaflets are held out in many angles.
The United Nations Food and Agriculture Organization details that bi-pinnate fronds are extremely rare in the Arecaceae, seen only in the group of palms known as fishtail palms. A bi-pinnate leaf looks like a pinnate leaf in structure, but a second branch occurs off the rachis. The leaflets are then held on these smaller, shorter second branches. A bi-pinnate frond has a general structure that looks like a fish's spine and ribcage skeleton.