Evoking images of tropical paradises, many types of palm trees (family Arecaceae) grow along coastlines, while others grace inland landscapes. The diversity among palm species includes towering giants that bear fruit to compact bush types that are perfect for smaller landscapes. Regardless of its species, a palm tree has unique botanical parts that differ from most conventional-looking broadleaf and coniferous trees, which include the following:
1. Palm Stems and Leaves
A palm's trunk is actually an elongated stem. Palms may be single-stemmed or multi-stemmed, with the stems ranging in texture from smooth to rough and even knobby. Many palms also have sharp spines along their stems.
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Like their monocot and coniferous plant relatives, palms have nutrient-transport systems inside their trunks, consisting of a xylem, which transports water and minerals, and phloem, which transports carbohydrates. Unlike the xylem and phloem in other trees that must continually be replaced when their old cells die, the xylem and phloem cells in palm stems remain alive as long as a palm is still living.
There are no lateral branches on palms that you'll find on other types of trees. At the top of a palm stem is the meristem, which is where leaves and fruit are produced. The quintessential postcard image of palms with long, narrow trunks and a cluster of leaves or palm tree fronds at the top of each trunk illustrates how the foliage is only produced at the top of its stem. If you have a palm, use a palm tree fertilizer to help prevent the fronds from curling and yellowing.
2. Palm Root System
Most palm roots extend laterally; palms have no taproots, although some of the primary roots do have some downward growth. As the roots emerge from the base of a palm, their diameter is fixed. This means that as the roots grow, they do not increase in diameter. When they emerge from the base of the plant, the diameter of roots is already established, although their length continues to increase.
Because there is no vertical taproot to anchor very tall palms, the horizontal root system may extend 50 feet or more from the trunk. Some palms produce so many roots that they split the base of the trunk, causing it to flare outward at ground level. The primary roots anchor a palm, and the other roots absorb water and nutrients that nourish the plant. There are no root hairs, common in other types of trees, which form a network that increases the amount of water and nutrients that a tree absorbs.
3. Palm Flowers and Fruits
Some palms are monoecious, which means that each plant bears both male and female flowers. Other palms are dioecious, which means each plant has either male or female flowers. Palm flowers form on flower stalks called inflorescences. Although the flower stalks on most palms grow from the leaf axils — where a leaf joins to the stalk — flower stalks on some palm species may grow from branch tips.
Although commonly called "fruits," these palm structures are botanically classified as "drupes." Coconuts and dates are notable fruits that grow on palm trees. Coconut palm (Cocos nucifera, USDA zones 10-11) and date palm (Phoenix dactylifera, zones 9-11) are the two trees that produce these commercial fruits.
Other types of palms also produce fruits, but they may not be edible or palatable. These fruits are important, however, for propagating more palm trees because of the seeds they contain, since palm trees generally can only be propagated from seed.