Common bean, green bean, Phaseolus vulgaris

They twine upwards on stalks, stand upright or as a bush: green beans are represented by hundreds of cultivated varieties worldwide. According to the latest studies on genetic material, the cultivated forms did not originate from the wild forms of the Andes, but from plants in Mexico and spread from there to other regions and to the Andes. The parent forms of today’s cultivated species are found in South and Central America, Africa and Asia, where they are still a staple food today. No wonder, as beans have always been an important source of protein for the human diet and a suitable vegetarian alternative to meat-based foods.

Colourful variety

Common beans are classified as a subfamily of the papilionaceous plants in the legume family. The annual garden bean grows in two varieties, either as a pole bean twining clockwise to the left or upright as a bush bean. All the leaves of the common bean are trifoliate, broadly ovate and alternate on long, thin stems. Lateral shoots emerge from their axils. The yellow, pink, white or purple bean flowers grow in axillary inflorescences and offer bees little nectar at this time of year. Self-pollination therefore takes place. The legumes each contain four to eight seeds. Not only do the beans come in different colors, the pods also come in different colors and shapes.

The common bean includes thousands of botanical varieties, such as the Italian Cannellini and Borlotti beans, Pinto beans from the USA and kidney beans from Peru. Despite being used in the same way, the runner bean, Lima bean and tepary bean are separate species within the Phaseolus genus alongside the common bean.

The common bean grows best at average temperatures between 18 and 30 °C. For healthy growth and a good yield, it needs rainfall that is as evenly distributed as possible and nutrient-rich, water-permeable soil. Heavy rainfall combined with high humidity can favor the development of numerous fungal diseases. In general, however, beans show a greater diversity of adaptation mechanisms to different locations, growth types and vegetation lengths than almost any other crop.

Staple food and beloved ‘sister’ in mixed cultures

According to recent research, the common bean was not cultivated from the wild forms of the Andes, but in Mexico an estimated 8000 years ago. From here, the cultivated forms spread to Central and South America. To this day, wild forms of the common bean, which provide important genetic resources for bean cultivation, can be found between Argentina and Mexico.

It is certain that farmers in Mexico and Mesoamerica have been cultivating the common bean for at least 7,000 years in a mixed crop together with maize, pumpkin and other crops. This traditional cultivation system, known as ‘milpa’ or ‘three sisters’, still provides food for the indigenous population of Central, South and North America today, but is increasingly threatened by the consequences of climate change. A variant of the cultivation system can be found in Colombia, where beans were grown in the coffee plantations to secure the basic food supply for the pickers. Smallholder mixed crops of beans and coffee can also be found in Africa.

In the 13th/14th century, the common bean was the food of the lower classes of the Inca population. From the 16th century, there are reports of them from Florida, later from Maine and in the north, cultivation reached as far as the St. Lawrence River. The common bean arrived in Europe in the 16th century and replaced the broad beans and cowpeas that had been cultivated until then.

According to the FAO, around 23 million tons of common beans and 28.5 million tons of dry beans were cultivated worldwide in 2022. China is by far the largest main cultivation country for green beans with almost 18 million tons, followed by Indonesia and India. India has by far the largest cultivation area for dry beans, followed by Myanmar and Brazil.

Healthy source of protein in global dishes

With their high protein content and essential amino acids, common bean seeds are an ideal source of vegetable protein in the human diet. They therefore also play a role in livestock farming, albeit a lesser one than soy or peas.

Beans also contain large amounts of minerals such as calcium, potassium, magnesium and iron as well as vitamins B2, B6, E, provitamin A, folic acid and especially vitamin C. Their carbohydrates are in the form of multiple sugar molecules, some of which cannot be broken down by humans, making beans a healthy, low-calorie vegetable. They also have what is known as the ‘second meal effect’ – thanks to their complex carbohydrates and high fiber content, beans ensure a slow rise in blood sugar and a stable energy supply for hours. This means that people who regularly eat pulses are less likely to get hungry. In their raw state, beans and their pods are poisonous as they contain substances that promote blood clotting. However, cooking destroys these so-called lectins.

While in Europe, North Africa and the Middle East the unripe ‘green’ pods of common beans (also known as French beans or – chlorophyll-free – wax beans) are also eaten as vegetables, the majority of dishes worldwide are based on dried bean seeds. In many countries in South and Central America, dried beans are even a staple food.

For example, they are a basic component of the Brazilian national dish feijoada, a bean stew. Gallo Pinto is the Costa Rican national dish and consists mainly of rice and black beans. Baked beans are particularly popular as a side dish in the USA. Depending on the region, different types of beans are included in chili con carne. Indian rajma dal is a variety of dal made from red garden beans. In France, cassoulet is made with white beans, while fabada is the Spanish version of this hearty stew. In addition to stews, beans are also used as an ingredient in many national soups, such as German and Serbian bean soup or Italian minestrone.

Ideally, dried beans should be used for the preparation, which should be soaked overnight (8-12 hours) and then cooked for at least another hour. Alternatively, pre-cooked beans are available in tins or jars. However, the vitamins suffer from the additional processing steps they have undergone.

The bean on the market: competitive?

Growing beans, especially on a large scale, poses a number of challenges for farmers: It has a high susceptibility to diseases and pests as well as comparatively low and, above all, unstable yields. Added to this are high market price fluctuations and – as a positive component – local preferences for certain seed types. As soon as crops with higher contribution margins offer a better option for land use, these crops are usually preferred for economic reasons.

Mexico’s semi-arid highlands are the largest contiguous bean-growing area in the world. In this region, which is characterised by low and irregular rainfall, the cultivation of beans is a good option for land use. However, maize is already gaining ground here in many places due to its higher profitability.

In Brazil, on the other hand, although beans are grown in all federal states, the most fertile and productive soils are increasingly being planted with soybeans, which are more profitable and in demand from the animal feed industry. This displaces bean cultivation to less favorable and less productive locations. This displacement to unfavorable soils leads, for example, to new diseases such as the golden mosaic virus and yield losses due to drought and low soil fertility.

One countermeasure would be to return to traditional forms of cultivation that are compatible with people and nature, such as milpa or other agroecological practices. Economic interests in short-term profits, lobbying and short-sighted political decisions and, as a result, the negative effects of climate change, are currently preventing this.

Sources

Pflanzenforschung.de: The cradle of the garden bean. Link.
Spektrum.de: Beans. Link.
Royal Botanic Gardens KEW: Milpas in Mexico: maintaining an ancient farming system. Link.