Over the next few lessons, we will explore nine of the more common plant families with cosmopolitan (worldwide) distribution. The goal is not necessarily rote memorization, but more to introduce the primary traits to be aware of when identifying plants.
This lesson will describe three of the easiest plant families to identify. You are already familiar with many plants from each of these families, as you’ll soon discover, but you may be surprised to learn how they are related.
As a brief recap: when studying plant taxonomy, the most useful tiers of the hierarchy are the top three: Family, Genus, and Species.
An organism’s genus and species name dictate its Latin name — Brassica rapa denotes that the organism is in the Brassica genus and bears the specific epithet rapa. (Note that Latin names are always italicized; Genus is always italicized and capitalized, while species is always lowercase.)
Binomial nomenclature isn’t so different from our two-name system for people: you could say that I am the species sam from the genus Benanti (my given name). And just like binomial nomenclature, my last name (genus) offers much more information about my key traits (Mediterranean features, Sicilian lineage) than does my first name (species), which may be shared by many unrelated individuals.
Similarly, when it comes to plant taxonomy, the most useful information you can have about a plant is often which family and genus it belongs to.
The specific epithet usually offers some Latinized bit of information about some key trait or where the plant is found, but this name may be shared by many unrelated organisms. For example, you’ll commonly encounter species names based on states like virginiana or ohioensis — the latter is shared by the Ohio Buckeye, the Ohio Goldenrod, and the prehistoric Giant Beaver (which was a rodent the size of a black bear!!), so it’s not very useful information if you don’t have anything else to work off of.
You can devote your time to learning the key characteristics of individual species if you’d like, but the real shortcut to identifying wild plants is to learn the major plant families. Once you are well acquainted with the following three families alone, you will be able to positively identify hundreds of species present in your local environment through the traits that they all have in common.
As we proceed into our exploration of plant families, we will focus in on the handful of key characteristics to look for in each one, while expanding our botanical vocabulary along the way. We will examine both wild and cultivated specimens wherever possible, and I would encourage you to devote a decent amount of time to Google Image Search to help you develop a sort of “composite” image in your mind of these families.
Lamiaceae - the mint family
Plants in the mint family are among the simplest to identify thanks to one very conspicuous trait: square stems.
If your specimen also has simple, opposite leaves, and it is aromatic when crushed, it almost certainly belongs to the Lamiaceae family.
Many of our most common cultivated aromatic herbs are members of the mint family, including:
Mentha - mint, peppermint, spearmint
Ocimum - basil
Origanum - oregano, marjoram
Salvia - sage
Rosmarinus - rosemary
Lavandula - lavender
Thymus - thyme
Wild mints are also very common throughout North America, especially in recently disturbed or compacted, marginal soil, where they often serve as early successional species and exhibit “weedy” tendencies. Nearly all are edible, though to varying degrees of palatability. Widespread genera include:
Lamium - henbit, dead-nettle
Glechoma - ground ivy
Marrubium - horehound
Perilla - shiso
Monarda - bergamot, bee balm
Hyssopus - hyssop
More on Lamiaceae:
Brassicaceae - the mustard family
Members of the Brassicaceae family are defined primarily by their flower and seed pod morphology.
Mustard flowers always have 4 petals and 6 stamens, of which 4 are taller and 2 are shorter. Seeds develop within distinct pods (“sillicles”) that radiate around the stem, along with the flowers, to form a raceme:
“a flower cluster with the separate flowers attached by short equal stalks at equal distances along a central stem. The flowers at the base of the central stem develop first.” - Wikipedia
Many of our most common cultivated veggies belong to the mustard family, including:
Brassica - kale, cabbage, collard greens, broccoli, cauliflower, kohlrabi, canola, etc.
Raphanus - radishes
Armoracia - horseradish
There are many common wild species of Brassica and Raphanus, and well as other wild mustards that are common garden weeds. All are edible, but some may be unpalatable due to intensity of spicy/peppery flavors. These include:
Cardamine - bittercress
Alliaria - garlic mustard
Capsella - shepherd’s purse
Barbarea - creasy greens
Rorippa - yellowcress
Nasturtium - watercress
More on Brassicaceae:
Fabaceae - the pea family
The Fabaceae family is the third largest family of plants, after Orchidaceae and Asteraceae, respectively.
These are our legumes, and essentially all species display distinct pea-like pods that we are all familiar with.
Plants in the pea family are also defined by their unique irregular, 5-petaled flowers, which are composed of 1 two-lobed banner, 2 wings, and 2 fused petals known as a keel. Only the Fabaceae family has “banner-wings-keel” flowers.
In the realm of horticulture, legumes are known as nitrogen fixers. Legume roots associate with soil microorganisms that allow them to chemically convert — “fix” — atmospheric nitrogen into a form that makes it available to be used by other plants. This is an utterly crucial ecosystem service provided by this plant family, and it’s why farmers who rotate their crops always incorporate legumes on a regular basis.
It’s also why legumes tend to be early successional species (just like mints and mustards) — they pave the way for later species with more fickle needs to arrive.
In terms of edibility, species in this family range from delicious & nutritious to mildly poisonous, so it is important to narrow your search down to at least the genus before consuming.
Common wild and cultivated legumes include:
Pisum - garden pea
Trifolium - clover
Medicago - alfalfa
Vicia - vetch
Gleditsia - honey locust
Lupinus - lupine
Acacia - acacia
Robinia - black locust
Apios - groundnut
Pueraria - kudzu
More on Fabaceae: