How Many Different Plant Species Do We Eat?

Edible diversity surrounds us, but we only know a sliver of it

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Just 15 crop plants provide 90 percent of the world's food energy intake

Food and Agriculture Organization of the United Nations, 2015

Staple foods: What do people eat?, The Food and Agriculture Organization of the United Nations, 2015, www.fao.org/3/u8480e/u8480e07.htm#:~:text=Just%2015%20crop%20plants%20provide,over%204%20000%20million%20people.

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How much diversity is there?

(Blue outline shows five different orders you can eat from just by eating five common edible weeds found in almost any neighborhood in the continental US)

Botanists catalogue plant diversity using phylogenies, like the one shown above for the flowering plants (also known as angiosperms). A phylogeny is just a tree-like diagram that shows the evolutionary relationships among distinct groups of organisms. In this phylogeny, the groups shown are clades, which means that every member of the group shares a single evolutionary common ancestor not shared by any other group’s members. So each branch tip on this phylogeny represents a group of organisms that are all more closely related to each other than to any other organisms on the phylogeny—and the phylogeny shows the evolutionary relationships among the groups.

The groups on this angiosperm phylogeny are orders. Orders are the fourth largest ranking out of the eight ranks commonly used in biological classification: species, genus, family, order, class, phylum, kingdom, and domain (listed smallest to largest). The angiosperms represent their own phylum, and it’s the largest, youngest, and most diverse phylum in the plant kingdom. You can get an idea of this by seeing how many different orders the phylogeny shows. In fact, about 80-90% of all plants are angiosperms.

There are about 20,000 plants edible to humans, nearly all of which are angiosperms.

Photo adapted from Mark C Brundrett (https://www.researchgate.net/figure/Position-of-mycorrhizal-lineages-in-a-simplified-angiosperm-family-tree-after-APG_fig3_227672792)

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Over 50% of the world’s caloric intake from plants comes from just three species in the same family.

Out of the approximately 20,000 plants edible to humans, only a few hundred are cultivated today. A number of incentives drive commercial agriculture to focus on only a handful of commodity crops, especially high-calorie ones such as corn, wheat, rice that can be used in a wide array of food products. All three of these grains come from the grass family, Poaceae, within the order Poales (see the monocot clade on the angiosperm phylogeny).

Photo: Adobe Stock (https://www.world-grain.com/articles/14061-indias-grain-production-on-the-rise)

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These six supermarket vegetables are all the same species

Since the beginning of industrialized agriculture, about 75 percent of plant genetic diversity has been thrown away as farmers moved toward a select few genetically uniform, high-yielding varieties. In almost all developing and developed countries, traditionally cultivated local varieties and landraces have been disappearing from agricultural practice as commercial varieties take their places.

Photo courtesy of Botanist in the Kitchen (https://www.sciencealert.com/these-6-common-vegetables-are-actually-all-the-same-plant-species)

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Wood Sorrel (from Oxalidales)

Wood Sorrel (Oxalis spp) is a common small lawn and garden weed from the Oxidales order, members of which typically have flowers with 5-6 petals and sepals (sepals are the green modified leaves at the base of a flower that protect and support the petals). See the angiosperm phylogeny to locate Oxalides.

Wood Sorrel has the classic “shamrock” shape leaf, though it is unrelated to clovers, and can have yellow violet, or white flowers depending on the variety.

Wood sorrel greens have a tangy, lemony taste due to the presence of oxalic acid (found in lower concentrations in other vegetables such as beet greens and kale), and are traditionally eaten raw as salad greens.

Photo credit Casey Reynolds, pHd, Texas A&M AgriLife Extension (https://aggieturf.tamu.edu/turfgrass-weeds/violet-woodsorrel/)

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Common Plantain (from Lamiales)

Common Plantain (Plantago spp) is one of the most common and vigorous imported European weeds across the Americas. Like mint, rosemary, and sage, it is from the order Lamiales, members of which typically have five fused petals and bilaterally symmetrical corollas (corollas are the whorl of flower petals considered collectively). See the angiosperm phylogeny to locate Lamiales.

Plantains have thick-stemmed leaves with prominent veins. The small greenish flowers grow on erect spikes. A single plant can produce over 10,000 seeds in one year, many of which can remain viable for over half a century, explaining in part the species’ colonization success in the Americas.

Plantain greens can be eaten raw or cooked, but have traditionally been used for medicinal properties, particularly because of their anti-inflammatory and anti-microbial compounds.

Photo from thefutureofhealthnow.com 

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Garlic Mustard (from Brassicales)

Garlic mustard (Alliaria petiolata) is another native European weed, likely imported for culinary use. Like broccoli and radishes, it is from the order Brassicales, members of which typically have high concentrations of mustard oils, and nectaries (the flower’s nectar production structures) located between the petals and stamens (the male fertilization organ which produces pollen). See the angiosperm phylogeny to locate Brassicales.

Garlic mustard has a biennial life cycle, starting out as a small rosette in its first year and growing a long stalk with seed pods its second year. It is often invasive in local communities, overrunning native species. A single plant will typically produce up to a thousand seeds, which are transported by wildlife and can remain viable for several years.

Garlic mustard greens have a similar taste to other mustard greens, and are traditionally used in the same ways. The roots have a strong horseradish taste and are used as a seasoning.

Photo credit Washington State Extension (https://www.kingcounty.gov/services/environment/animals-and-plants/noxious-weeds/weed-identification/garlic-mustard.aspx)

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Dandelion (from Asterales)

Dandelions (Taraxacum spp) are one of the most common lawn weeds in North America. Like Sunflowers and Lettuce they belong to the order Asterales, members of which typically have achenes, small, one-seeded fruits that do not open to release the seed. The achenes of dandelions are carried on parachute-like structures that allow them to be carried long distances by wind. See the angiosperm phylogeny to locate Asterales.

The entire dandelion plant has traditionally been eaten in Europe and North America, though it is usually eaten in the first year of its life cycle, before it becomes too bitter from accumulated defensive compounds.

Photo courtesy of All Safe Pest Control( https://allsafe-pest.com/services/lawn-care-and-weed-control/)

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Purslane (from Caryophyllales)

Purslane (Portulaca oleracea), native to Persia, is one of the most common weeds around the world. Like cacti, it is from the order Caryophyllales, members of which typically have succulent, fleshy stems and leaves. See the angiosperm phylogeny to locate Caryophyllales.

Purslane has only a one year life cycle, and can propagate from broken stem pieces or from seeds, which can remain viable for as long as 50 years. Purslane is an extremely persistent weed, and is highly drought-tolerant because of its succulent stems and leaves, and waxy cuticle.

Unlike most other weeds, purslane is widely eaten around the world and in the United States as a salad green. It can frequently be found in farmers markets, and is often curried or stir-fried.

Photo courtesy of The Old Farmer’s Almanac (https://www.almanac.com/purslane-weed-benefits-and-recipe)