Legumes are extremely important to farming and food production because they have a symbiotic relationship with a type of bacteria, Rhizobia. Rhizobia colonize plant roots, pull nitrogen from the air, and convert it into a type of ammonia that plants can use. The plant then makes amino acids which are combined into proteins.

Legumes are used by farmers to enrich the soil. The major plant nutrients are nitrogen, phosphorus, and potassium. Phosphorus and potassium are part of the mineral content of the soil and are relatively stable in comparison to nitrogen. Newly tilled soils and forest floors (a planting surface created by the ancient slash and burn method of farming) have plenty of nitrogen. After a field has been farmed for a few years, the nitrogen is depleted. Early on, farmers discovered ways to increase the soil’s nitrogen content. These included 1)planting in river valleys subject periodic flooding which deposits rich soil in the flood plain, 2) adding combinations of manure and plant debris (what we now call compost), and 3) planting and tilling in legumes prior to grain and other crops. Use of legumes to enrich soil was known by ancient Greeks and Romans, with surviving Greek texts from 400 BC mentioning such use. However, the actual chemistry of the nitrogen fixing process was not discovered until the 1880s.

Worldwide, legumes provide about 10 percent of the protein consumed by humans; however, unlike protein from animals, legumes do not provide a “complete protein” in that they do not contain ALL the amino acids we need to make our bodily proteins. Again, long before scientists knew about elements, amino acids, and proteins, we had learned to eat legumes with a grain—corn, rice, or wheat—to promoted health and growth.

There is a multitude of healthy legume/grain combinations.  For example, I spent a significant part of my youth eating pinto beans that were simmered for hours on the stove and served with fresh-baked cornbread. This was a particularly prevalent meal on the days immediately prior to my dad getting his Saturday paycheck. According to the Oxford Companion to Food, published by Oxford University Press, Ful Medames or Ful Mudammes is the “single most famous bean dish” in the world. It originated in Egypt as a breakfast dish of long-simmered fava beans served warm pita bread.

Beans. Beans are described as a remainder category in the Oxford Companion on Food, namely, as “Any legume whose seeds and pods are eaten and which is not classified as a pea or lentil.” This seems like an odd definition me. What about peanuts? But maybe those Oxford University Press folks had heard the song Goober Peas, and think of the peanut as a pea.

But back to beans.

The majority of beans are used in their dried form. When a bean dries, its pod or hull becomes thin and papery allowing easy removal of the seeds. They can them be cleaned and stored nearly indefinitely. Harold McGee who authored the famous text, On Food and Cooking, the Science and Lore of the Kitchen, speculates that people initially consumed green or fresh beans. Dried beans are not easy to digest, and he believes consumption of dried beans came after cooking was invented. Supporting his theory is the observation that breeders did not develop new varieties of  fresh beans until recently.

Initially, green beans were climbing varieties and were native to Central America and the Andes. Within the past 200 years, breeders have developed cultivars with tender shells and special colors (yellow and purple), that grow in bushes, and that are string-less—without the fibrous strip that holds the two halves of the shell together. Seed catalogues still sell varieties with strings, and many people still refer to all fresh beans as string beans.

Currently, most of the beans available in the Durham Farmers Market are fresh beans. When I was young, all beans were cooked until limp and with “seasoning,” a fatty, cut of pork called fat-back, or with bacon. Now it is more popular to lightly cook or steam beans and to served them with butter, olive oil, and possibly lemon.