Palms in Comparison to Trees
Horticulturalists and Botanists Categorize Palms as Grasses
A little Backstory
I began working in the horticultural industry as an inexperienced, yet fiercely curious student before graduating from an undergrad plant science program. I had a burning rage to know everything and found myself absorbing whatever facts I could from the more seasoned professionals. Occasionally, palms were a subject from these professionals. These experts LOVED discussing their admiration for this plant. I consider palms as an identity for these interesting individuals who were wrapped up in the horticulture world.
My mentors would explain to me that palms were to be maintained and treated a lot differently than “trees”. I never questioned it, just regurgitated what was told to me. Until one day at the San Diego Botanic Garden I found a scroungy looking “stump”. As of today, I am yet to identify the species of palm that is shown below. The reason why I like this picture is because it helped me glue the pieces of plant anatomy. This is definitely a monocot of some sort. It’s not a palm, but it got me sniffing around palm anatomy and physiology.
Figure 1: unknown stump found in a planter at San Diego Botanical Garden; image taken by an iPhone 8.
Palms Are Monocots
Flowering plants (angiosperms) are divided into two groups called monocots and dicots. They can either be one or the other. Each individual species’s development determines which group they are categorized into. The monocot group contains grasses and other grass-like plants, while all other flowering plants are considered dicots.
Order: Arecales
an order of flowering plants
Family: Arecaceae
the only family within the order Arecales, and it contains only palms
Palm Roots
The palm root ball consists of a shallow mass made up of adventitious roots. Trees on the other hand, are deeply rooted by a taproot. Palms will often put out aerial roots, which are the result of root initiation developing under and parallel to the palm’s most basal portion of the stem (see fig. 4).
Palm propagation initiates from seeds or by physically spreading. Trees on the other hand, may be propagated from a variety of methods (depending on the species).
An Interactive Activity: pull a dandelion and pull a clump of grass from the earth. Notice the larger, longer center of a root attached to the dandelion. This is the taproot. The grass has many fibrous roots which allows most grasses to spread easily.
Leaves vs Fronds
Palm leaves are called fronds! Fronds are evergreen. New fronds emerge from the center of the canopy and unfold.
The surface area of a single fronds is usually much larger in comparison to leaves from trees. Check out this study surveying carbon fixation and ozone absorption rates.
Figure 2. Fronds of a Washington Fan Palm (Washingtonia filifera)
Tissues
Palms lack the annual rings found in trees. The width of the palm is not correlated with time. There is no increase in width from the palm’s stem as it ages.
Slicing a stem revealing a cross section displays the anatomical difference between monocot and dicots.
Figure 3. A diagram displaying the basic anatomical difference between dicot and monocot stems via cross section.
Basic Rules for Palm Care
Fertilizing
We highly recommend using fertilizers specially blended for palms. You will want to look for fertilizers with high potassium (K) content.
Tip: Palms exhibit potassium deficiency by the browning of older leaves. You’ll usually notice the tips of the fronds browning as it gradually progresses to the petiole base. Potassium deficiency symptoms distinctly differ by palm species.
Planting
Plant palms during warm seasons. If you happen to be in a cooler climate, plant in the beginning of warm season.
Palms are easier to transplant compared to trees due to their adventitious root system and root initiation zone. When making root cuts, it is highly favorable to cut roots the furthest away from the trunk as possible. The larger the root ball available, the more successful you will have a successful establishment. Visit this research paper for a more in depth understanding.
Pruning
Palms do not need to be pruned often. Old leaves usually fall from palms on their own. In cases of preventing disease dispersal, it may be recommended to remove the affected fronts.
A good tree trimmer company typically use lifts to allow the trimmer to reach such great heights. Cheap (and bad) trimmers will use “spikes”. When actual trees are damaged on the outer surface of their trunks, they perform a process of healing. Palms lack the ability to produce secondary growth (they don’t become wider). Wounds created by spike’s impact remain on palm trunks forever. Open wounds like this can become infected with pathogens.
Check out this source from University of Florida (Palm PDF).
Figure 4. Cross section of palm stump showing different tissue layers
Recommended Resources
Transplanting:
https://edis.ifas.ufl.edu/pdffiles/EP/EP00100.pdf
Palm Root Growth:
https://ucanr.edu/sites/UrbanHort/files/80174.pdf
Palm Morphology and Anatomy:
https://edis.ifas.ufl.edu/ep473
Palm Nutrition and Fertilization:
https://www.researchgate.net/publication/287116219_Palm_Nutrition_and_Fertilization
University of California And Natural Resources, Don Hodel’s:
