The Notanist's Guide to Understanding Floras and Dichotomous Keys

To be continually revised
Notanist: A portmandeau of "not" and "botanist." It means exactly what it sounds like it means.


Tip 1: Don't overwhelm yourself. Start small.

I would not recommend starting out with Flora of North America. There is often such a large amount of species that you will quickly be overwhelmed. Even US state-level might be too much, depending on how big or ecologically diverse aforementioned US state is.

Work first from a smaller local flora book; I used Flora of North Central Texas. Once you feel comfortable, work up to something larger. Exceptions would be any groups or genera with relatively few species. It's easier to start working from several local species than a dozen or so nationwide.


Tip 2: Have a botanical glossary on you. With illustrations/images. And maybe a few other sources to check vocabulary.

There is no way a layperson would be able to read a flora book. Botanical terms practically consist of a completely different language!

As confusing as it may seem, there is a purpose to this language, which is to make keys, descriptions, and other botanical works considerably more concise. Think of the terms as shortcuts: "pedicel" instead of "stalk holding flower to stem," rachis instead of "that stem-like part which runs through the center of the compound leaf." Concise words versus botanical charades. To the student of botany, though, they present a large obstacle in deciphering keys and descriptions.

Solution: have a good botanical glossary on you, preferably one with illustrations if you're just starting out. A picture is a thousand words, so they say, Botanical terminology is significantly easier if you have an image of the part which said term corresponds to. I use Plant Identification Terminology: An Illustrated Glossary by James G. Harris and Melinda Woolf Harris. In addition to the traditional alphabetical glossary, terms are also sorted by category (leaf shape, stem indumentum, inflorescence types) which I find rather convenient. In lieu of an actual book, the GoBotany website has an online pictorial glossary one can use.

It's useful to have multiple sources to refer to. Sometimes a term will have multiple definitions. Pubescent can refer to having short, soft hairs, or having any kind of hairs. As with finding out the meaning of any sort-of word, look at the surrounding words and sentence for context in order to determine the definition.

You may need multiple sources to get an understanding of the definition of a term. This could include a normal dictionary and Google. Images are always helpful if you can find good ones.


Tip 3: Working from a larger flora? Simplify the key; rule out unlikely candidates

This applies to field guides as well. Start by eliminating species that are not known to occur in your area. I use BONAP (Biota of North America Program) maps, which organizes county-level maps by genus, so it's easy to determine which species in a genus occur in your county. The USDA plants database also has maps with its species profiles as well (you can zoom in on the maps to show county). With the USDA site you could also go to genus and check subordinate taxa maps, although I prefer BONAP for that. Also, if your flora book has a page with distribution maps for species, prioritize those as they will probably be more accurate than the other two mentioned.

Once you know what species occur in your area, you can focus on only those species in the key, which makes things more manageable. For example, where I live only C. involucrata, C. leoicarpa, and C. pedata occur, so in the FNA key I can focus on those three rather than all 9 of them.


Tip 3: Don't understand it? Take your time. Work couplet by couplet, word by word.

Sometimes you will grasp a couplet immediately. Sometimes... you won't. If you encounter the latter case, reread the couplet, with your botanical glossary. Know what the words mean. Though understanding the meaning of the words is not always enough, which leads me to my next point...


Tip 3: Know which character corresponds to what on the plant

Aka know the plant's morphology. Where is character X on a plant?

A short explanation of characters and character states:

  • Character: anything that can have more than one form/variation. Examples: Petal color, inflorescence type, leaf shape
  • Character states: things used to describe a character state. Examples: Red/white/light pink, panicle/cyme/raceme, ovate/deltoid/lanceolate

Leaves lanceolate
Character is the leaves, character state is lanceolate

Sometimes, the petals are a lie; they're actually sepals! In all seriousness, though, it's difficult to understand whether the bracts on a plant are auriculate or lanceolate if you don't know which part of the plant is the bract.

A flora book with illustrations may be of great help here, especially if you're just beginning. Look at images of other plants in the genus. Reading the genus description might help too. It will get easier with experience.


Tip 3: Referencing images: iNaturalist observations, herbarium specimens and other images can be accurate, but not always. Check them with literature, take them with a grain of salt.

Misidentifications happen, whether on iNat or in the herbarium, and that is something to be aware of. Take them with a grain of salt. If working from iNaturalist observations, find an observation from an botanically-experienced user, someone who does understand floras and dichotomous keys. Those are significantly more likely to be accurate. Check those "examples" with the literature.

Herbarium specimens can be more accurate with identifications. Also, they are often pressed/arranged such that you can see everything you need for identification e.g. top/bottom of leaves, calyx or phyllary details, flowering pedicel length. Specimen sheets are often available to view online at various websites. Take advantage of those too.


Tip 4: It comes with time. Be stubborn, eventually you will get it.

It took me approximately 2 years to "get" floras and dichotomous keys. It won't happen overnight. Be meticulous and stubborn. I will do anything in my power to get a plant to species, if possible. When overly frustrated with something, shelve it and return to it later.

Publicado por arnanthescout arnanthescout, 24 de noviembre de 2022

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