Broad Bean (Vicia faba)

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Broad bean (also known as fava bean) is a widely cultivated legume crop belonging to the Fabaceae family. It has a long tradition of cultivation in Old World agriculture, being among the most ancient plants in cultivation and one of the easiest to grow. Beside being used for human consumption, it is also cultivated as a cover crop to prevent erosion and fix nitrogen in the soil and small seeded varieties are fed to horses and other animals.

The beans, with the outer seed coat removed, can be eaten raw or cooked. Some people – especially of southern European ancestry – might suffer from favism, a hemolytic response that results from a consumption of large quantities of fresh fava beans and leads to muscle weakness, paralysis and, in severe cases, death.

Growing recommendations

Fava beans are a fast-growing, hardy, cool-weather annual crop that can be planted in either early spring or fall in most areas and grown year-around in mild climates (subtropics and tropics, at higher elevations from 1 300-3 800 meters for the latter). The plant can grow in well-drained light (sandy), medium (loamy) or heavy (clay) soils, with a mildly acidic or neutral pH. While fava beans prefer moist soil and full sun, they can tolerate drought to a certain extent as well as partially shaded areas.

Fava beans can be direct seeded at about 3-5 cm depth, then lightly covered with some mulch. Rows should be roughly 60-90 cm apart. Note that the germination can be speeded up by soaking the seeds in water for 12 to 24 hours before sowing. Once planted, the seeds will germinate at temperatures ranging from 12-24° C in 5-10 days on average. Plants grown for seed production should then be thinned out to 10-15 cm. This will constrain the emergence of diseases. They will also need to be staked (the earlier the better to avoid disturbing the roots once they mature), which will also facilitate the harvesting process when the time comes.

Common diseases and pests

• Bacterial diseases: Bacterial brown spot (Pseudomonas syringae)
• Fungal diseases: Chocolate spot (Botrytis cinerea, Botrytis fabae), downy mildew (Peronospora viciae), fusarium root rot (Fusarium solani), powdery mildew (Erysiphe pisi),
• Insect pests: Aphids (pea aphid, bean aphid, cowpea aphid, melon aphid, peach aphid, etc.) (Acyrthosiphon pisum, Aphis spp., Myzus persica), broad bean rust (Uromyces viciae-fabae), leafminers (Lyriomyza spp.), Mexican bean beetle (Epilachna varivestis), thrips (Western flower thrips, onion thrips, etc.) (Frankliniella occidentalis, Thrips tabaci).
• Mites: Spider mites (two-spotted spider mite) (Tetranychus urticae)
• Oomycetes: Leaf blight (Xanthomonas campestris
  syn. Xanthomonas axonopodis)
• Nematodes: Root knot nematode (Meloidogyne spp.)

Pollination, crossing, and isolation

Depending on the climate and variety, fava beans can take between 80 and 100 days on average to reach maturity. It is in flower from May to August and the seeds ripen from July to September. The flowers, being an important source of nectar, are very attractive to bees. They are 1 to 2.5 centimeters (1⁄2 to 1 in) long with five petals; the standard petals are white, the wing petals are white with a black spot and the keel petals are white. Crimson-flowered broad beans can also be found. While the plant is self-fertile – with the pollen being transferred to the stigma when the flowers are disturbed by the wind – its hermaphrodite flowers can still be pollinated by bees. Crossings with other species remain rare, but can therefore still occur – to an even greater extent in areas where sources of pollen are usually scarce. Adequate isolation distances should be applied accordingly in order to ensure seed purity. If several varieties are grown simultaneously and in closer proximity, the use of caging or bagging isolation techniques will be necessary.

General seed saving guidelines (harvesting and processing)

Each bean pod contains 3–8 seeds. They are round to oval, 20–25 mm long, 15 mm broad and 5–10 mm thick in average (food cultivars). The pods are usually left to dry on the plant itself. However, in case of unfavorable weather, pods can be harvested earlier when still green or the whole plant pulled out and allowed to dry further in a protected warm area. Doing the latter will allow the seeds to mature further, which will result in higher quality seeds. The pods can be somewhat difficult to thresh due to the seeds’ hilum being firmly attached to the inside of the pod. If small quantities of seeds are to be processed, the pods can be hand shelled in a relatively short amount of time with the help of several people. While this method is slower, it allows a better control and assessment of the seed quality and makes the cleaning process easier. In case of larger batches, the dry pods can be placed inside a bag or laid out on a tarp and trampled over or beaten with a stick. If the seeds require additional cleaning, those can be winnowed by pouring them from one bowl to another in front of a light breeze or small fan, allowing the chaff to be blown away. Cover the area with a tarp to retrieve any seed that has been carried by the wind and clean it after each new variety to avoid any accidental mixing.

Like most Fabaceae seeds, fava beans are very susceptible to bean weevil, whose larvae typically infest and develop inside the seeds themselves. By slowly chewing their way into and out of the seed (leaving easily recognizable holes), weevils can cause irreversible damages resulting in its death. To prevent this common pest from damaging the seeds, those that are fully dried, cleaned, and ready for storage should be put into an airtight container and frozen for five days at -15° C. This will kill any weevil eggs that are present. Note that any seed that is taken from frozen storage and transferred to a temperate environment should be allowed to reach room temperature before opening the container in order to prevent condensation.

Broad bean seeds will remain viable for an average of six years when stored under optimum conditions.