From South America to Midwest Canning Jars
The Strange Story of the Modern Green Bean
This story was supported by Oregon vegetable farmers and the Oregon Processed Vegetable Commission.
When you sit down to a holiday dinner and serve yourself a heaping helping of green bean casserole, you’re participating in an activity that dates back to humanity’s earliest origins. People have been eating pods filled with seeds in some capacity for a very, very long time — since Homo sapiens shared the planet with other members of our genus. Charred remains of prehistoric meals from the Shanidar Cave in northern Iraq reveal that Neanderthals were dining on vetch and peas as long as 75,000 years ago (the archeological record remains mum on whether they were served with a crispy onion topping).
The Great Big Bean Family
Beans are members of the Fabaceae family, one of the largest families of plants on the planet. Native to every continent except Antarctica, it contains more than 20,000 species ranging from diminutive poisonous vines to towering tropical trees. Its edible constituents are nutritious, dense in protein and calories, easy to grow and harvest, and suitable for long storage, which has made them a staple food for cultures in hot and temperate climates around the world.
In addition to being good to eat, they’re also good agricultural partners. Rather than deplete land, beans actually improve the places they grow by fixing nitrogen in soils for other crops to use later. Beyond food, legumes are also grown for animal forage, fertilizers and crop rotations, timber, and the production of fabric dyes, gums, and oils. One could wake up in a bed built from acacia, pull on a shirt dyed with indigo, then sit down to a breakfast of pinto beans flavored with a bit of bacon made from pork raised on soybeans — four encounters with Fabaceae before you even leave the house.
The green beans in your casserole, however, are a relatively new version of an ancient plant: Phaseolus vulgaris, or the “common bean.” There’s nothing vulgar about it. Phaseolus vulgaris is native to Central and South America. It appears to have had two distinct primary centers of domestication: One in Central America, around what is now southern Mexico; and the other in the Andes in South America, near what is now Peru. Large-seeded beans, including kidney beans, trace their origins to the center of domestication in South America. Medium-seeded types like pintos and pink beans come from the arid highlands of Central Mexico, while the smaller beans like black beans are from the tropical regions of lowland coastal Mexico.
From those epicenters, cultivars of Phaseolus vulgaris spread throughout the Americas, where they became a staple food crop for many Indigenous people, who grew them alongside squash and corn in a famous planting style known as the three sisters. Today, Phaseolus vulgaris is grown around the world, ranging from tiny ebony black beans to huge ivory nuggets larger than a human thumb.
From Stringy to Snappy
Oregon’s Blue Lake snap beans are related to those mid-sized beans, which means its story begins in the highlands of Mexico. The beans Indigenous north and central Americans were eating before European contact probably didn’t resemble the modern snap bean very closely. While ancient Americans ate all portions of the bean, including the pod, those pods were likely quite tough. There’s some evidence from quids, which are wads of chewed vegetable matter like yucca, tobacco, agave, and other plants often found in human settlements in the Southwestern United States and northern Mexico, that people would even munch on the pods and then spit out the particularly stringy bits.
Breeding geared specifically towards developing a stringless, tender pod only began after colonialism introduced Phaseolus vulgaris to Europe around 1530. Europeans were already acquainted with a range of culinary beans, including cowpeas, broad beans, lentils, and garbanzo beans. Perhaps it was because of this familiar aspect that European farmers readily accepted this new variety of bean, unlike their cautious posture towards other unfamiliar American crops like potatoes and tomatoes , whose close European relatives are highly poisonous.
Over time, populations of Phaseolus vulgaris developed in Europe that were primarily consumed as an immature pod, rather than grown to maturity to harvest only the seed. What inspired European farmers to select for these characteristics? Could it have been their existing familiarity with the relatively tender-podded garden pea? Or might they have had trouble growing beans to maturity at all in the cooler climate of continental Europe, leading them to routinely harvest immature pods? It’s difficult to say, although breeder Jim Myers suggests that there’s a pattern of European farmers selecting for tender vegetable characteristics from field or storage crops introduced from the Americas. Zucchini and cocozelle squash, for instance, were selected from New World pumpkins, favoring a smaller size, juicer flesh, and tender skin over the sturdy shell and long storage properties that had been selected by growers in more arid climates.
Still, early green beans retained some stringiness — hence their old-fashioned name, string beans. It wasn’t until the 1880s that the truly stringless green bean was developed. Calvin Keeny, a plant breeder for the Burpee Company, introduced Burpee’s Stringless Green Pod in 1889, marking the first commercial availability of stringless string beans (“snap” beans is a nod to the fact that stringless beans can be snapped cleanly in half).
The Genetics of Flavor
Today, virtually all commercial beans are stringless, although some older people likely still remember the pleasant task of de-stringing fresh green beans before dinner. The main attraction of the green bean today is its pod: crisp, juicy, and full of verdant flavor. The actual bean seeds are somewhere between an afterthought and an irritation. Seeds that get too big, starchy, or prominent are undesirable. (A green bean pod with one over-mature bean is called a polliwog, and breeders try to avoid them whenever possible.)
There are eight distinct genetic groups of modern snap beans, which means that those tender “snap” characteristics were selected for in multiple sites. Tendercrop, a variety of green beans grown widely in the Midwest, are genetic descendants of the South American line. Blue Lake, a variety prominent on the West Coast, descends from beans originally domesticated in Mexico. You can taste the difference. Tendercrops are high in linalool, an organic compound with a fruity, spicy, floral character (it’s also found in lavender, citrus fruit, and hops). Bite into a Tendercrop and you’ll taste its perfumed, slightly bitter flavor.
Blue Lakes are higher in 1-octanol , the other key compound responsible for green bean flavor. Also found in asparagus, mushrooms, and cabbage, 1-octanol gives Blue Lakes a savory, almost meaty flavor with a long, savory finish that tastes great with classic green bean accompaniments like bacon or toasted almonds. Both varieties are undoubtedly different than what those Neanderthals were dining on in the Zagros mountains of northern Iraq 75,000 years ago, but they’d certainly have recognized them as something good to eat.
