Vicia faba

Vicia faba, known as the broad bean, fava bean, or faba bean, is a type of vetch in the Fabaceae family. It is grown widely for human food and as a cover crop; smaller, harder-seeded varieties fed to animals are called field bean, tic bean, or tick bean. Many cuisines around the world use this legume. People with favism—a hemolytic reaction to eating broad beans linked to the metabolic disorder G6PDD—must avoid them. For others, the beans can be eaten raw or cooked once the outer seed coat is removed. Young pods allow the seed coat to be eaten, and very young pods can be eaten whole.

The plant is a stiffly erect annual, 0.5 to 1.8 meters tall, with two to four square stems. Its leaves are 10 to 25 centimeters long, pinnate with two to seven leaflets, and grey-green. Unlike most vetches, it lacks tendrils for climbing. Flowers are 1 to 2.5 centimeters long with five petals: white standard petals, white wing petals with a true black spot, and white keel petals. Crimson-flowered varieties, recently saved from extinction, also exist. The flowers have a strong sweet scent that attracts bees and other pollinators.

The fruit is a broad, leathery pod, green at first then maturing to dark blackish-brown with a dense downy surface. Wild pods are 5 to 10 centimeters long and 1 centimeter wide, but many modern food cultivars have pods 15 to 25 centimeters long and 2 to 3 centimeters thick. Each pod holds three to eight seeds. Wild seeds are round to oval, 5 to 10 millimeters in diameter; food cultivars produce flattened seeds up to 20 to 25 millimeters long, 15 millimeters wide, and 5 to 10 millimeters thick. V. faba has a diploid chromosome number of 12, with five acrocentric pairs and one metacentric pair.

Its diploid genome contains 13 GB of DNA, mostly from retrotransposons and satellite repeats. This is one of the largest diploid field crop genomes, with a predicted 34,221 protein-coding genes.

Broad beans have a long history in Old World agriculture, among the most ancient and easiest crops to cultivate. Their wild ancestor is unknown, but charred legumes of a possible wild-type progenitor were found at the Natufian site of el-Wad Terrace. Carbonized domestic remains from three Neolithic sites in Israel’s Lower Galilee—Yiftah’el, Ahi’hud, and Nahal Zippori—suggest domestication may have begun as early as 8250 BCE. They are still grown as cover crops to prevent erosion, overwintering and fixing nitrogen. Broad beans are hardy, tolerating harsh, cold climates and, unlike most legumes, high salinity and clay soil, though they prefer rich loams.

In much of the English-speaking world, “broad bean” refers to large-seeded cultivars for human food; “horse bean” and “field bean” refer to smaller, harder seeds used for animal feed, though their stronger flavor is preferred in some human dishes like falafel. “Broad bean” is common in Commonwealth countries (UK, Canada, Australia, New Zealand), while “fava bean” is used in the United States.

Diseases are more frequent in high humidity, so cultivars bred for higher density should be evaluated for disease problems. West–east rows can increase sun drying. Disease tolerance is key in breeding. Transplanting instead of direct seeding lowers the risk of some diseases, including Botrytis fabae.

In mainland Europe and North Africa, the parasite Orobanche crenata (carnation-scented broomrape) can severely devastate broad bean fields.

Botrytis fabae, the chocolate spot fungus, is one of the worst diseases in broad beans, causing foliar damage, reduced photosynthesis, and lower yield. It switches from non-aggressive to aggressive under increased temperature and humidity, worsened by low soil potassium and phosphorus and by higher seeding rates. The non-aggressive phase shows small red-brown lesions on leaves, stems, and pods. Treatment is less effective than prevention. Early planting avoids the problematic late-spring-to-early-summer conditions. Decreasing seeding rate or thinning after emergence helps. Foliar fungicide is effective. Flowering during peak summer heat raises disease risk. Transplanting reduces Botrytis fabae outbreaks.

Powdery mildew species like Erysiphe baeumleri are not uncommon on Vicia species. Resistant cultivars and overhead irrigation are preventive; sulfur fungicides are recommended for severe outbreaks.