How palms work

A cabbage palm tree (Sabal palmetto) silhouetted
by a sunrise on the St. Johns River.

Palms decorate tropical and subtropical regions of the World

Palms are monocots. Angiosperms or true flowering plants are divided into two major groups—monocots and dicots, which have various differences, but are named for the number of seed leaves or cotyledons they have. 

Monocots also include grasses, orchids, gingers, bananas, and bamboo. Also, most of the bulbs including onions, garlic, lilies, tulips, and more, but probably most important characteristic for our discussion on palms, there is no real wood with annual rings. The vascular tissue (the phloem and xylem) in monocots is arranged in bundles throughout the stem. In a dicot, they occur in the cambium layer just under or inside the bark around the plant stem. It is the new set of xylem and phloem cells that are produced each year which form the annual rings that produce the wood in true trees.

A comparison of a monocot (left) and a dicot stem cross section. In a monocot, the xylem and phloem are in bundles throughout the stem.

This palm stump shows that it's fibrous and that there are no annual rings.

How does a palm grow?

All the growth takes place in the crown: both the flowers and the fronds. This where the apical meristem is located and each year this moves upward. The trunk doesn't get thicker each year like a real tree with wood formed by new growth each year.

A cabbage palm in its palmetto state when it puts out frond after frond to build up the girth of the trunk or the stem as the apical meristem develops. Once there is adequate girth, then the tree begins to grow vertically. This may take 10 years or more.

If there are no annual rings and no wood, how does a palm develop into what looks like a tree?

Palm seedlings may take years to develop and gain enough girth before they begin to grow vertically. Palms grow fronds and inflorescences or flower heads only from their apical meristems, which moves vertically upward as it produces new fronds. The apical meristem is also known as the heart of palm and depending upon the species, it can be 3 or 4 feet long and up to a foot or more in diameter. It’s labeled as the crown in the above diagram. Once a palm tree is growing vertically, it will never increase in girth, which is why some palms look so darn skinny. Depending on the species, you may be able to see growth rings on their stems. These are leaf scars.

This root zone of a palm tree shows that there are a lot of roots, but since there is no wood, these roots do not damage the infrastructure such as sidewalks or pools by expansion.

Because there is no wood and no cambium layer, palm trunks can’t heal wounds. These injuries are not fatal like girdling a real tree with wood, but it does weaken the tree.

Also, since there is no wood, the roots can never expand and therefore do far less damage than real trees where the roots grow thicker each year, which is why they are often selected for landscapes near foundations, sidewalks and pools. They may growth thousands of roots as seen in this photo, which is normal. But, with all those roots, they may crowd out other plants. And since there is no cambium layer, palms can't heal or grow over places that have been damaged, so it's best to remove lawn grasses away from palms. 

The Palm family: (Arecacacae)

The palm family (Arecacacae): the fruits are drupes (like a peach) that range in size from less than 1/2" in diameter to 50 pounds for the double coconut. Palms can have single trunk or multiple trunks. Some are shrubs where the stem is recumbent. More than 600 are vines.

There are about 2600 species in the palm family, which vary widely, but all are native to the tropics and subtropics. There are single trees, multiple-stemmed trees, shrubs (or recumbent palms usually called palmettos, at least in Florida). All the fruits are drupes, with a single pit like a peach. Plants are classified by the fruit and the flower. Some of the fruits are tiny, about the size of a BB, while others are huge, one is native to the Seychelles Islands, the Double Coconut, aptly named due to the massive fruits of these palms may weigh more than fifty pounds. Most palms have edible fruit, but some are toxic. Some of the palm fruit yields oils. The fronds or leaves can be quite large and can be palmately divided or fan-shaped, pinnately divided like a feather, or undivided. And, surprisingly, there are more than 600 species of palm vines, which are most often used as rattan to build furniture. Unlike the bamboo, rattan has a strong core (remember those xylem and phloem bundles that we talked about in the center of the stems). So rattan is durable and hard to break.  It is generally steamed to mold it into varied shapes. 

Florida's palms

There are 29 different species in the palm family (Arecaceae) that occur in Florida, but 11 species are native to Florida, including Florida's state tree, the cabbage palm (Sabal palmetto). The native palms are:

- Everglades palm (Acoelorraphe wrightii)
- Florida silver palm (Coccothrinax argentata)
- Key thatch palm (Leucothrinax morrisii)
- Sargent’s cherry palm (Pseudophoenix sargentii)
- Needle palm (Rhapidophyllum hystrix)
- Florida royal palm (Roystonea regia)
- Scrub palmetto (Sabal etonia)
- Bluestem palmetto (Sabal minor)
- Cabbage palm (Sabal palmetto)
- Saw palmetto (Serenoa repens)
- Florida thatch palm (Thrinax radiata) 

Read about Florida's Native Palms in this article by Georgia Tasker.

Cabbage palm (Sabal palmetto)

The cabbage palm is a fan palm with a native range that includes all of Florida and northward to southern North Carolina and westward to Louisiana. It's a slow growing, but long-lived plant and while it acts like a tree in the landscape, it's not a real tree because it doesn't produce wood. So, what does it say about Florida (and South Carolina) that the state tree is not a true tree?  

Cabbage palms can retain their boots, which are bases of old fronds, along their trunks or not.

A grove of cabbage palms after a fire. Some of the lower boots are blackened. 

Harvesting a cabbage palm. This tree might have been 40 or 50 years old.

The apical meristem is the "Heart of Palm." Here it's being used as a "cabbage" in a stew. They turn brown right after harvesting, so they must be used or preserved right away.

When planted in landscapes, this palm is usually planted as an adult tree with almost all of the fronds and roots trimmed off. They develop all new roots upon planting, but since that may take a year or more, most newly planted palms are staked in place. At no other time should green fronds be trimmed away. The so-called hurricane trim is unnecessary and is harmful to the tree. In most cases, no trimming is ever needed--the dead fronds will drop when ready. Cabbage palm trunks may or may not retain the bases or old fronds and this does not indicate anything about their health.

Indigenous peoples and early Florida settlers used these palms in many ways, including harvesting their hearts (apical meristem) for food. The taste and texture is reminiscent of cabbages, hence the common name. But harvesting the heart will kill the tree, and since these palms are not as plentiful as the in the past, this tradition is fading. 

Note: Most of the hearts of palm that we consume today are from peach palms (Bactris gasipaes), which is a small, multi-stem palm that's native to South America. This is more sustainable, since the stems grow from a mat and can be harvested in only two or three years and when the stem is cut, it does not kill the palm. The other important characteristic is that these palm hearts don't turn brown after harvesting so they can be shipped fresh. 

Saw palmetto (Serenoa repens)

A small fan palm that grows in clumps or dense thickets in sandy coastal dunes and as undergrowth in pine forests. It usually grows only 4 to 8 feet tall. Populations of this species in nature may represent clones of a single individual, which has slowly spread over hundreds, perhaps thousands, of years. Unlike most palms, saw palmetto has a creeping or recumbent trunk that branches, and so a single plant can eventually cover a large area. Wildfires in its native habitat will burn off the foliage, but new leaves push out within days. Plants often flower following a burn. They are tough plants that can withstand both flooding and drought, plus they are somewhat tolerant of salt spray.

A saw palmetto thicket next to our front pond.

The recumbent trunk of a saw palmetto.

Other palms in Florida

Coconut palm (Cocos nucifera) is native to Australia, but was domesticated twice: in India and in SE Asian islands. The strain from India was planted in the Caribbean and in Florida. On January 9 in 1878, the Spanish brig Providencia was en route from Cuba to Spain. Its cargo, 20,000 coconuts, was scattered along the coast. The settlers of Florida knew an opportunity when they saw one and planted most of the stranded coconuts in their yards and along streets. The coconut palms and groves that grew from these seeds later gave Palm Beach County its name. Today it's commonly planted in all of South Florida. 

Queen palm (Syagrus romanzoffiana) is native to South America, but has been widely planted in Florida and has pread into wild areas of the state. It is now is considered to be and invasive species in Central and South Florida according to the Florida Invasive Species Council. 

For more information:
- My 2011 FNPS palm article
- An IFAS cabbage palm article.
- My Transplanted Gardener palmetto article
- The Palmetto Book: The Histories and Mysteries of the Cabbage Palm by Jono Miller
- Kew Gardens Where do palm trees grow

GreenGardening Matters,
Ginny Stibolt