Can I eat this? What makes something edible

Amelachier berries. Photo by Claire Collie

Amelachier berries. Photo by Claire Collie

All over the city of Buffalo berries on Amelachier bushes are ripening to a deep red. Most shrubs in this genus are native to temperate North America and berries are important for foraging wildlife. 

This year I learned that I could be part of the foraging wildlife. 

Amelachier berry is super sweet - think of a sweet blueberry and then make it sweeter! These berries go by many names: juneberry, shadblow, service berries, or Saskatoon are all common monikers. In western Canada the berries were an important source of vitamins to the Native tribes, and became a staple in the prairie settlers diet. 

Now, as I walk through the city and pass a bush, I take a few berries and contemplate the idea of edibility. How can I eat an Amelachier berry, but not the leaves? Why can we eat lettuce leaves, but not grass or maple leaves? 

What makes something edible? 

Two basic things: you can digest it and it isn’t toxic.

Our diet contains all sorts of plant parts. Roots, stems, bark, fruits, leaves, nuts and seeds are all things we eat daily. (If you’re not you should be, especially now, as this seasons local fruits are ripening!) Plants don’t want most of their parts to be eaten. Like animals, the goal of a plant is to reproduce. If we eat the leaves, flowers or seeds of a plant we may have successfully hindered production of future offspring. To deter herbivory plants contain compounds that are either toxic or indigestible to humans. 

Some of these chemicals, called alkaloids, are toxic to herbivores. Alkaloids interfere with the nervous system and can lead to mild sickness or death if enough is consumed. Poison hemlock, which contains a host of compounds, is so toxic that small amounts can kill an animal by causing muscle paralysis. Consuming tobacco leaves, which contain the alkaloid nicotine, leads to stomach cramps, nausea, seizures, and death. Some alkaloids, like caffeine, have useful benefits at low doses. Others are extracted, purified, and used as pharmaceutical or recreational drugs. Codeine, morphine, and cocaine are all alkaloids from plants.

 
I only eat the tenderest of salad greens. Photo by Claire Collie

I only eat the tenderest of salad greens. Photo by Claire Collie

Goats eat tender greens too. The field our goat friends lived in is mowed twice a year because they can't keep up with the growing grasses. Photo by Claire Collie

Goats eat tender greens too. The field our goat friends lived in is mowed twice a year because they can't keep up with the growing grasses. Photo by Claire Collie

 

The very nature of plant cells aides in their in-edibility. Plant cells, unlike animal cells, have ridged walls. Cellulose and lignin keep plant cell walls ridged. Lignin physically and chemically makes plant parts, especially old plant parts, indigestible by most herbivores. Stiff lignified cell walls allow upward growth and water movement within a plant. 

Most plant leaves we eat are relatively young and tender. As leaves and plants get older the cell walls become more lignified, tough and not so tasty. Pea shoots are a good example. They are not very well known in the US outside of community supported farms, but they’re delightful in early spring. Young shoots of recently sprouted peas have a nice grassy, pea flavor. If you wait too long, the stems become tough and stringy as cells within the stem become older and more specialized in their function. Grazing animals, like cows and goats, don’t like eating tough, old leaves either. This is one reason rotational grazing is important.

Ilex verticillata (winterberry) in New England woods are food for many bird species, but poisonous to humans. Photo by Claire Collie

Ilex verticillata (winterberry) in New England woods are food for many bird species, but poisonous to humans. Photo by Claire Collie

Fruits aren’t always edible either.

Many colorful, delicious looking berries are quite toxic to humans. Fruits from Ilex genus look lovely in the winter, but their cocktail of acids, alkaloids, and tannins in a small handful can kill a curious child. Some fruits, like hyacinth beans, are poisonous unless they are cooked in multiple changes of boiling water. If in doubt, it’s best not to eat a fruit you are unsure of. 

If you have ever bit into an unripe apple it probably didn’t taste good. The bitter, spit-inducing flavor is the result of tannins, and is a clear indicator that the fruit is not ready to be eaten. Tannins are produced so unripe fruits aren’t eaten. Furthermore, eating unripe fruits reduces survivorship and growth of an herbivore. If you were to eat a bunch of unripe apples you would probably feel sick to your stomach. In our long human lifetime this probably wouldn’t have too much effect on your survivorship, but you wouldn’t make the same mistake twice.

As a fruit ripens it goes through many chemical changes. Sugars accumulate (tasty!), cell walls break down (less lignin and cellulose that can’t be digested), and organic compounds like organic acids and tannins disappear. There is often a change in color, from green to bright red, or blue or orange, depending on the species. These showy colors are for our benefit and are the plants way of saying ‘eat me!’ 

Ripening blueberries. Photo by Claire Collie

Ripening blueberries. Photo by Claire Collie

Why would a plant not want it’s leaves eaten, but spends a lot of energy producing a fleshy fruit? Fruit-producing plants need animals to disperse their seeds. When an animal eats a fruit, like birds eating Amalachier berries, the seeds are taken away and dropped in a new place. In modern times, we humans are no longer good seed dispersers in the traditional sense (although we’ve done a fair job at moving plant species all over the world in other ways). 

There are lots of plants, or plant parts that are edible, but aren’t part of our diet. Carrot tops, young squash leaves and radish seed pods are all things I’ve tried. Have you eating any unusual food that is a common plant? 


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