The Matrix

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The Matrix was developed by Dr. Humberto Jimenez Saa as a way of teaching dendrology, the science of tree identification, to students of all levels. It builds upon early work by Dr. Leslie Holdridge, a pioneer in tropical forestry and tropical ecology, aimed at elucidating plant families using only vegetative material. In tropical forests, leaves and bark are almost always available, but flowers and fruits are seasonal and often hidden from those of us who cannot access the canopy the same way as a monkey, bird, or bee. Traditional plant identification and classification is based on flowers which are readily available to most temperate zone botanists, but not easily accessible in most tropical forests.

Strictly speaking, The Matrix is not a taxonomic key. It does not set out to identify any and all plant specimens. It doesn’t even claim to work all the time. BUT it works MOST of the time and is relatively easy to use once you learn some basic terminology and agree to follow the routine described in How To Examine A Plant.

Using the matrix…

The Matrix consists of eight sections and can fit on a mere 6 pages. Each section is based upon phyllotaxy (alternate, opposite, or whorled), leaf type (simple or compound), and the presence or absence of stipules. Once these three basic pieces of information have been determined, it is a matter of identifying the combination of two or three other traits that allow you to determine the family to which a plant belongs. So get yourself a branch with some leaves on it and follow the routine until you can assign your specimen to the proper family.

Please note that The Matrix is not complete. Each user may develop his or her own version of the matrix utilizing features that are easily remembered or observed by the user. As your botanical knowledge increases, you will certainly want to expand the matrix to accommodate your expanding list of plant families and genera. The Matrix presented here was constructed by Scott Shumway with the help of Dr. Jimenez as part of a course in Tropical Dendrology. The Matrix may be reproduced, but Dr. Humberto Jimenez should be properly credited as its creator. Please note that this matrix is restricted to dicots. In the future I hope to add a section for monocots.

About Dr. Humberto Jimenez

Dr. Humberto Jimenez

To truly appreciate the beauty of The Matrix and to master it, you should take one of the Tropical Dendrology courses offered by Dr. Humberto Jimenez.

Dr. Humberto Jimenez is an inspirational teacher. His deep connection to and passionate love of trees is infectious. It is hard to imagine anyone with a greater knowledge of tree identification. As a teacher, he is firmly committed to sharing this knowledge with his students or anyone with an interest in trees. After studying with Humberto, you will have a newfound appreciation for every tree, leaf, or stipule that you encounter anywhere in the world. His love of trees and zeal for teaching is matched by a love of life and hope for the future of humanity. He measures his remaining time on Earth by the need to identify and label as many plants as possible, and freely admits that he has at least another 50-60 years left before his work will be complete. Until then, he will continue to tell us “here’s another tree for you to study…”

Dr. Jimenez' dendrology website is located at:


-by Scott Shumway and Humberto Jimenez

Key to the eight sections of the matrix based on phyllotaxy, leaf type, and stipules.

  1. Alternate – Simple Leaves – No Stipules
  2. Alternate – Simple Leaves – With Stipules
  3. Alternate – Compound Leaves – No Stipules
  4. Alternate – Compound Leaves – With Stipules
  5. Opposite Or Whorled – Simple Leaves – No Stipules
  6. Opposite Or Whorled – Simple Leaves – With Stipules
  7. Opposite Or Whorled – Compound Leaves – No Stipules
  8. Opposite Or Whorled – Compound Leaves – With Stipules


Turpentine odor, juvenile lvs red, resin dries dark, Ex: Anacardium, Mangifera Anacardiaceae
Distichous, ranalean odor, string bark, pagoda branching, fibers in live bark, Ex: Annona, Xylopia Annonaceae
Petioles of varying lengths, little horns at base, Ex: Dendropanax, Oreopanax Araliaceae
Obovate lvs clustered at branch tip, sympodial branching, buttresses, Ex: Terminalia Combretaceae
Rank odor, wavy leaf margins, pointy buds, irregularly flattened twigs, 1-seeded berry ± cupule, Ex: Nectandra, Ocotea Lauraceae
Pseudoterminal stipule, brown black dots (lines), Ex: Ardisia Myrsinaceae
Swollen nodes, rat-tail inflorescence, odor, Ex: Piper, Peperomia Piperaceae
Citrus odor, pellucid dots, crenate margins, (spines), falsely simple, Ex: Citrus Rutaceae
Simple & compound, bad tuna odor Roupala (Proteaceae}
3-veined common, perma-press, irregular margins, abundant pith Asteraceae
Pseudo-opposite, anisophylly, rank odor, * hairs, (spines) Solanaceae
3-way branching: 2 horiz + 1 shorter vert, swollen nodes, Ex: Cordia Boraginaceae
White or watery latex, coleters, paired fruits, Ex: Thevetia, Plumeria Apocynaceae
Raspy leaves both sides, 2° veins parallel, reddish bark, mostly lianas, bejucos de agua Dilleniaceae
Distichous, ranalean odor, myristicaceous branching, large seed & red aril, Ex: Virola Myristicaceae

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