Phaseolus vulgaris are a versatile vegetable, producing attractive, long, thin pods, and creamy haricot beans. They are a heavy cropper, with each plant producing potentially hundreds of beans from each single bean sown. Like many other types of bean, they are a great nutritional source of protein and iron, and offer superb value as the seed can be saved and resown from year to year.
I. Appearance and Characteristics
Phaseolus vulgaris, the common bean, is a herbaceous annual plant grown worldwide for its edible dry seeds or green, unripe pods. Its leaf is also occasionally used as a vegetable and the straw as fodder. Its botanical classification, along with other Phaseolus species, is as a member of the legume family Fabaceae. Like most members of this family, common beans acquire the nitrogen they require through an association with rhizobia, which are nitrogen-fixing bacteria.
Bush varieties form erect bushes 20–60 centimetres (8–20 inches) tall, while pole or running varieties form vines 2–3 metres (7–10 feet) long. All varieties bear alternate, green or purple leaves, which are divided into three oval, smooth-edged leaflets, each 6–15 cm (2–6 in) long and 3–11 cm (1–4 in) wide. The white, pink, or purple flowers are about 1 cm long and have 10 stamens. The flowers are self-pollinating, which facilitates the selection of stable cultivars. The flowers give way to pods 8–20 cm (3–8 in) long and 1–1.5 cm wide. These may be green, yellow, black, or purple, each containing 4–8 beans.
Some varieties develop a string along the pod; these are generally cultivated for dry beans, as green stringy beans are not commercially desirable. The beans are smooth, plump, kidney-shaped, up to 1.5 cm long, range widely in color and are often mottled in two or more colors. The beans maintain their germination capacity up to 5 years.
Like most species from Phaseolus, the genome of P. vulgaris has 11 chromosomal pairs (2n = 22). Its genome is one of the smallest in the legume family at 625 Mbp per haploid genome.
Raw or undercooked beans contain a toxic protein called phytohaemagglutinin.
The common bean has a long history of cultivation. All wild members of the species have a climbing habit, but many cultivars are classified either as bush beans or climbing beans, depending on their style of growth. The other major types of commercially grown beans are the runner bean (Phaseolus coccineus) and the broad bean (Vicia faba).
Beans are grown on every continent except Antarctica. Worldwide in 2022, 28 million tonnes of dry common beans were produced, led by India with 23% of the total.
Raw dry beans contain the toxic compound phytohaemagglutinin, which can be inactivated by cooking beans for ten minutes at boiling point (100 °C, 212 °F). The US FDA also recommends an initial soak of at least 5 hours in water which should then be discarded.
II. How to Grow and Care
Sunlight
Beans need full sun for the best yield. Full sun also helps to keep the plants dry and less likely to be affected by certain issues, such as fungal diseases.
Temperature and Humidity
Common beans germinate best when the soil temperature is between 70 and 80 degrees Fahrenheit. If the soil temperature is below 60 degrees, seeds will germinate more slowly and are susceptible to rot. The plants grow best when the air temperature is between 65 and 85 degrees Fahrenheit. Beans tend to stop flowering in the extreme heat of summer. But keep them well-watered, and they will resume flowering and production when temperatures cool. Moreover, common beans grow in all humidity conditions if properly watered.
Watering
The Common bean is a very thirsty plant, especially when developing flowers and fruits. As long as the soil has good drainage, they can be watered daily. As moisture on leaves and stems may cause rot or disease, try to water the soil around the plant’s stalk 鈥?or, water when the sun is out so that any surface moisture will dry out quickly.
Soil
Beans like organically rich loamy soil with a slightly acidic pH. Good soil drainage also is key. Remove weeds prior to planting to prevent competition for soil nutrients and moisture. As the beans grow, weed carefully around the plants, as their shallow roots are easily damaged.
Fertilizing
Common bean is a nitrogen-fixing plant that usually require little, if any, soil amendments. A layer of compost, applied in early spring, can help ensure your plants are getting all the micronutrients they need, however. If your soil is highly phosphorus deficient, applying a low-nitrogen fertilizer mix (e.g., a 5-10-10 ratio mix) or bonemeal may be appropriate.
Pruning
No pruning is necessary for common beans, other than pulling the plants from the ground as cold weather sets in. These are annual plants that do not return the following spring. Allow the beans to continue to grow as long as possible, as these legumes actually improve the soil by absorbing nitrogen from the air and fixing it in the soil. Some gardeners like to rotate the planting location of legume species like beans and peas around the garden to take advantage of this soil-improving property.
Propagation
Bean plants are propagated via seed. Because the plants are annuals, this is an inexpensive way to ensure you have new plants each year. Here’s how to save the seeds:
- Harvest seed pods from a healthy bean plant once the pods have dried and become brittle.
- Break open the pods to release the seeds.
- Store the seeds in a dark, dry, cool spot within an airtight container. They should be viable for three to four years and can be planted in the spring after the threat of frost has passed.
- Be aware, however, that only non-hybrid, open-pollinated plants will produce seeds that grow into plants identical to the parents. If you try this with hybrid varieties, you are likely to be disappointed with plants that do not have the same characteristics as the parent plant.
How to Grow from Seed
Bean seeds are generally direct sown in the garden, as they dislike being transplanted. Their roots are shallow and easily damaged. If you want to start beans inside, plant them in biodegradable pots or soil blocks that can be planted into the garden once the weather has warmed.
Potting and Repotting
A quality potting mix that’s labeled for vegetables is usually ideal for growing beans. As long as you plant in a large enough container, you won’t have to repot these annuals and disturb their roots during the growing season.
Pests and Diseases
Several animal pests love bean plants, including:
- Mexican bean beetles will eat the flowers, the beans, and especially the leaves.
- Spider mites pierce the leaf surface and suck the sap, often causing leaves to die.
- Japanese beetles and aphids may also attack bean plants.
- Bean leaf beetles can girdle the stems near the soil line and chew holes in the plant’s leaves.
- Deer and groundhogs will eat entire bean plants, and fencing is necessary to stop them if they are prevalent in your area.
Fungal diseases, such as Alternaria leaf spot, can be a problem in damp conditions. Other diseases, including white mold, bean rust, and mosaic virus, can also affect bean plants. Help prevent diseases by keeping the vines dry. Also, don’t overcrowd the plants, and provide plenty of air circulation. You can look for plant varieties that are bred for disease resistance.
III. Uses and Benefits
- Dry beans
Dry beans will keep indefinitely if stored in a cool, dry place, but as time passes, their nutritive value and flavor degrade, and cooking times lengthen. Dried beans are almost always cooked by boiling, often after being soaked in water for several hours. While the soaking is not strictly necessary, it shortens cooking time and results in more evenly textured beans. In addition, soaking beans removes 5 to 10% of the gas-producing sugars that can cause flatulence for some people. The methods include simple overnight soaking and the power soak method, in which beans are boiled for three minutes and then set aside for 2–4 hours. Before cooking, the soaking water is drained off and discarded. Dry common beans take longer to cook than most pulses: cooking times vary from one to four hours but are substantially reduced with pressure cooking.
In Mexico, Central America, and South America, the traditional spice used with beans is epazote, which is also said to aid digestion. In East Asia, a type of seaweed, kombu, is added to beans as they cook for the same purpose. Salt, sugar, and acidic foods such as tomatoes may harden uncooked beans, resulting in seasoned beans at the expense of slightly longer cooking times.
Dry beans may also be bought cooked and canned as refried beans, or whole with water, salt, and sometimes sugar.
- Green beans and wax beans
The three commonly known types of green beans are string or snap beans, which may be round or have a flat pod; stringless or French beans, which lack a tough, fibrous string running along the length of the pod; and runner beans, which belong to a separate species, Phaseolus coccineus. Green beans may have a purple rather than green pod, which changes to green when cooked. Wax beans are P. vulgaris beans that have a yellow or white pod. Wax bean cultivars are commonly grown; the plants are often of the bush or dwarf form.
As the name implies, snap beans break easily when the pod is bent, giving off a distinct audible snap sound. The pods of snap beans (green, yellow and purple) are harvested when they are rapidly growing, fleshy, tender (not tough and stringy), and bright in color, and the seeds are small and underdeveloped (8 to 10 days after flowering).
Green beans and wax beans are often steamed, boiled, stir-fried, or baked in casseroles.
- Shelling beans
Shell, shelled, or shelling beans are beans removed from their pods before being cooked or dried. Common beans can be used as shell beans, but the term also refers to other species of beans whose pods are not typically eaten, such as lima beans, soybeans, peas, and fava beans. Fresh shell beans are nutritionally similar to dry beans but are prepared more like vegetables, often steamed, fried, or made into soups.
- Popping beans
The nuña is an Andean subspecies, P. v. subsp. nunas (formerly P. vulgaris Nuñas group), with round, multicolored seeds that resemble pigeon eggs. When cooked on high heat, the bean explodes, exposing the inner part in the manner of popcorn and other puffed grains.
- Other uses
Bean leaves have been used to trap bedbugs in houses. Microscopic hairs (trichomes) on the bean leaves entrap the insects.
From ancient times, beans were used as devices in various methods of divination. Fortune-telling using beans is called favomancy.
P. vulgaris has been found to bio-accumulate zinc, manganese, and iron and have some tolerance to their respective toxicities, suggesting suitability for natural bio-remediation of heavy-metal-contaminated soils.
IV. Harvesting and Storage
Harvesting beans is an ongoing task, and the more you pick, the more beans the plants will set. You can start to harvest anytime after the beans form. Gardeners usually harvest the beans when the pods are young and tender, about the size of a small pencil. The inner seeds should not yet be visible through the pods. Overly mature beans, where the inner seeds can be seen bulging through the walls of the pod, can be tough and stringy.
In general, bush beans are ready to pick in 50 to 55 days after planting. Pole beans will take 55 to 65 days, depending on the variety. Check the packet to be sure your choice will have time to mature in your growing season. Harvest by gently pulling each bean from the vine or by snapping them off at the vine end. Be careful not to damage the plant when harvesting. You can cook the beans right away or blanch and freeze them. They can keep in the freezer for up to a year.
Find Where to Buy the Best Common Bean (Phaseolus vulgaris)
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