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Fairchild’s tropical garden column: Palms with bite

The murumuru palm is aggressive in many ways; it is covered entirely by large spines and it is a strong grower.
The murumuru palm is aggressive in many ways; it is covered entirely by large spines and it is a strong grower. Fairchild Tropical Botanic Garden

When we think of palms, images of solitary stemmed, erect palms that lack any protection against predators come to mind. This classic palm has a smooth trunk, soft leaves and rounded fruit. Most landscape palms are like this — nonthreatening. This “classic” palm relies on heavy fruit set to combat predation; it leaves the viciousness to the cactus and bromeliad. But thinking only of the stereotype leaves out a whole slew of great palms.

Vicious palms have mastered the art of self-defense and have developed spines to protect their leaves, fruit and stems, mostly from being eaten. Although different palms have different predators, typically they include raccoons and rodents.

Palms are extremely diverse in their armor. Leaf spines protect the photosynthetic unit — the powerhouse that captures energy from the sun. Fruit spines protect the palms’ precious reproductive unit — the seed. The stem spines are also highly effective. No predator can approach the palm to feast on seeds or leaves if the stem is heavily armored.

However, just like we would lock the front door and turn on the alarm, palm species with a lot of predators may have more than one type of spine to protect themselves. The most vicious palms have a combination of these defense mechanisms to ward off the most aggressive predators.

Palms can produce spines in two ways. Sometimes it is a modified palm part (modification spines). Most commonly, a leaf or root changes in form in order to protect the plant. In other cases, the spine is formed from epidermal or underlying tissue. This type of spine is an emergent spine.

While formation and anatomy of the spine may be different, the result is almost identical: armature on almost any part of the palm. Palm spines can be found on leaves, leaf sheaths, and trunks. For each type of armature, there are examples of palms that grow beautifully in southern Florida. This interesting and diverse group of vicious palms can make a great addition to your collection.

A spine created from a modified palm part is very common. A leaf can change in many ways to protect the plant. The base of the leaf where it connects to the trunk is called a leaf sheath. In some palms, the leaf sheath is fibrous. In these fibrous leaf sheaths, some of the fibers become spine-like. Our native Rhapidophyllum hystrix gets its common name — needle palm — from its leaf sheath spines.

In the wild, this clumping palm grows on rich soil that overlays limestone. If you are one of the lucky Miamians who has a deep soil pocket in your backyard, plant the needle palm and remember to water. This palm is always thirsty.

A relative of the needle palm is the zombie palm (Zombia antillarium). The multi-stemmed zombie palm has sharp spines protruding from leaf sheaths as well. It is better suited to our southern Florida growing conditions. If you are looking for an easy grower with awesome armature, the zombie palm is for you.

The name root spine palm (Cryosophila williamsii) is a dead giveaway of spine formation type. Since palms are able to initiate roots along the trunk (think about the roots that form high above soil level on sidewalk-planted royal palms), these spines cover the majority of the trunk. While the name conveys the formation, it does not describe the awesomeness of the phenomenon — soft spines, sometimes even branching two or three orders, grow prolifically on the trunk. They are great growers so I suggest you plant one and enjoy its exquisiteness.

When discussing modification spines, it’s hard to ignore the Phoenix palms (Phoenix spp.). This group of palms forms spines from modified leaflets at the base of the leaf. These palms are common in the landscape and grow well in southern Florida. However, they are often hungry and their spines are very dangerous. I don’t suggest planting one in your backyard.

Emergent spines may look similar to modification spines but their anatomy is quite different. Emergent spines are formed from underlying tissue that grows out to form spines. The spine wasn’t modified from another part of the palm, it’s formed from cells programmed to be spines. Most commonly, teeth develop along margins of the petiole (the stalk that connects the leaf blade to the trunk). Teeth can be easily seen in many great landscape palms: paurotis palm (Acoelorrhaphe wrightii), bailey palm (Copernicia baileyana) or Corypha utan.

The paurotis palm is a wonderful, colonial palm but it has high water requirements. The bailey palm is a slow grower, but be patient because its columnar trunk is magnificent. Corypha utan is an incredible palm that flowers only once. It produces millions of flowers, sets fruit and then dies. A rare palm in its armature and reproductive behavior, it’s every collector’s dream palm.

Emergent spines can be found almost anywhere on a palm. The Cuban belly palm (Acrocomia crispa) has brutal, densely packed spines on the trunk and leaves. But these spines are more prevalent on younger individuals and as the individual grows, the spines become less dense. Like most Cuban palms, the Cuban belly palm prefers full sun and dry conditions.

Another great grower with emergent spines is the murumuru palm (Astroscaryum murumuru), which is entirely covered with gigantic spines. Emergent spines cover the trunk, leaves and fruit and make this palm an astounding site. Plant this palm in a shady spot and make sure to keep your distance.

While commonly cultivated palms lack spines, many great growers are covered in armor. By ignoring this group of vicious palms, we lose out on many wonderful palms that we could add to our collections. While these palms require a little extra care and precaution, they should not be overlooked. Any of these spined palms would look impeccable in your backyard; just keep your dogs and children at a safe distance.

Sara Edelman is the palm and cycad manager at Fairchild Tropical Botanic Garden.