Common Beans stats/requirements at a glance
|Ease of Raising:||2/5 – Biweekly check-ups|
|Water:||2/5 – Twice a week|
|Sun:||4/5 – Full sun, shade tolerant|
|Training:||3/5 – Some, support with stakes|
|Fertilise/Feeding:||3/5 – Monthly, half strength liquid fertiliser|
|Time to Harvest:||3/5 – Moderate, 2-3 months|
|Frost Hardiness:||2/4 – Tender, can’t cope with mild frost|
|Most Problematic Nemesis:||Black bean aphids|
Beans are best known for bean soup – a reliable, easy to come by and nutritious food supply, especially during winter for suppers. Dry beans come in a huge variety of shapes, colours and flavours. Several canned varieties are also available, ensuring year round supply of bean goodness, but you won’t find me eating red sauce beans on toast – I much more partial towards eating cannellinis! However, in the vegetable garden, green beans are more suited and economic to produce. They are a delight to grow as they germinate with ease and once in production will likely generate more beans than you can eat!
Beans are some of the oldest cultivated vegetables with archaeological remains dating back to 5000 BC. Their origins lie in mountainous regions of central and south America where separate domestication by local tribes lead to distinct gene pools; one the Andes population (containing 26% of the diversity of the ancestral population) and the Central or Mesoamerican (with 46% ancestral diversity). Subsequently, beans travelled to Europe in the 16th century along with the Spanish and Portuguese ships.
Beans have remained the primary pulse crop in tropical America, where it is grown as one of the “Three Sisters” with squash and maize. Its distinct populations have remained largely intact with some overlap in genetic identity as well as distribution in the overlapping range between Mexico and South America, see map in this article for more details (REF 1). Although the overlapping region contains both populations; more migrants are observed from the Andes population towards the Mesoamerican population (References 1-3, “A reference genome” pdf contains a map of the genetic spread of the populations).
The common bean has several names, such as French, kidney, haricot, snap, string and frijoles. They are all grouped under dwarf or bush beans, due to their compact growth. These are further classified according to their pod structure:
- String or snap: round/flattened pods
- Stingless: pods lacking the fibrous spine
Most cultivated beans belong to the Phaseolus genus, including the common bean, Phaseolus vulgaris. Runner beans are slower to produce than bush varieties, but are more prolific and belong to a different species, Phaseolus coccineus. All beans are nitrogen fixing, they convert atmospheric nitrogen to bio-available nitrogen in the soil with the assistance of symbiotic bacteria (Rhizobia) contained in their root nodules and thus they add nutrients to the soil. Peas and beans belong to the same family of leguminous plant, Fabaceae (synonymous with Leguminasae or Papilionaceae) and also include soybean, peanuts, alfalfa and clover.
The seed packages bought in store specify growing them in summer, but I have found that common beans (P. vulgaris) grow better as a winter crop in South Africa. I have grown runner beans in summer, but for this article I am concerned with the common bean. Considering that bush beans are native to mountainous regions of South America, it also makes more sense to me that they would prefer cooler growth conditions.
Beans are easily raised from seed in early autumn. Direct seed them into their permanent spot in the garden as they do not transplant well. They do well in pots of 20 cm depth for optimum root development and water drainage. Bush beans do not require supports, but I prefer to secure them to a short stake when they start to flower. The plant can become top heavy due to pod formation and a gush of wind can bend and damage the plants if they are kept unsupported. Beans are not frost hardy, therefore protection from early frost might be necessary with frost netting. You can feed them – I usually fertilise once every two-four weeks with half-strength liquid feed.
Keep your eye out for any ant activity or shiny leaves (honeydew deposits), which may be indicative of black aphid infestation, especially towards the end of the season when most of the plant energy goes towards pod development. These nasty little mongrels can easily get out of hand as winter sees a lack of natural enemies. A spray with my environmentally friendly organic treatment should keep them at bay until the plant is spent and removed (Biological/Green Pest Control, Aphid Control).
Other Bean plant Tips
I would recommend some pruning of overcrowded leaves and even some flowers, especially in the centre of the plant. Due to its compact nature, bean plants can entangle themselves in their own stems, this hampers proper growth and leaf development as well as providing a sheltered place for pests. Once the plant has reached it full size 30-50 cm, prune away some of the leaf, stem and flower spire bulk towards the centre of the plant. I aim to get the plant to produce more flower spires towards the outside of the plant, which allows for full unrestrained pod development and easy harvesting. If you want to harvest seed, set aside some pods dry towards the end of the season.
Be careful of not perpetuating legume-disease (such as chocolate spot, a fungal infection) by planting your peas/beans and green manures in the same bed season after season, try to rotate the crops with non-legumes or interplant with non-legumes.
Harvesting and Storing
Green beans are the young pods containing immature seeds, which are ready for harvesting in 8-10 weeks from planting. Stringed varieties are picked before they become fibrous, whereas stringless varieties can be picked when desired. Beans will produce more prolifically when you continuously harvest them from the plant well before the pods mature. Cut the pods from the plant with a pair of scissors, since yanking might damage the parent plant.
Beans are best enjoyed fresh, although surplus can be frozen by topping and tailing, chopping into 2.5 – 5cm lengths. Afterwards they are blanched for 1-2 minutes, drained, cooled and properly dried before freezing. Frozen beans can keep for up to 12 months.
Dry beans can be collected once the pods have become brown and rattle when shaken. Dried beans are easily collected from the pods and stored in glass jars as long as they do not become mouldy or shrivel. Dried beans contain more protein than green beans Dry beans contain an anti-nutritional toxin, known as lectin (a phytohaemagglutinin), which is deactivated by either soaking the dry beans for 5 hours (dispose of water afterwards) or boiling the beans at 100oC (212oF) before consumption.
Beans bare perfect flowers in a raceme (spire), which open at night and are self-pollinated. Cultivar preservation does not require isolation by distance as flowers do not easily cross-pollinate, but tall barriers can be erected between stands should pure ‘stock’ be required. Flowers come in a variety of colours (white, yellow, pink and violet) and are very similar to the papillonaceous (butterfly) flowers of peas. Pods and beans are just as colourful with green, red, purple, yellow, black and white with several streaked combinations. Pods contain 4-6 beans and some do not retain their vivid colours once cooked.
Bush varieties flower, fruit and mature in a short amount of time. The pods are botanically classified as a dehiscent (dry) fruit. Seeds are mature when the pods become dried husks. The pods are removed and cured for another 1-2 weeks in a brown paper bag, this will allow the pods to break open and release the beans into the bag. Allowing the beans to be released naturally from the pods ensures that the protective seed coat remains intact which is crucial for germination. The beans can be stored in the paper bag or glass jar and can be saved for up to 3 years. Beans germinate when the soil temperature reaches 16-29oC (60-85oF), where warmer soil promotes quicker germination.
Something interesting – Jumping Beans
Jumping beans are a little bit of a misnomer as they are not truly related to legumes. The seeds of such plants are known to twitch when handled giving their name ‘jumping beans”. The beans ‘jump’ due to the presence of a moth larvae (type of parasitism). Females lay their eggs on the young seeds, which hatch and larvae burrow into the seed. They hollow out the inside and spin a cocoon with the larvae suspended inside by silk threads. When disturbed by an environmental stimulus, such as the warming of the seed when held, causes the larvae to pull on the threads making the seed twitch. It is a protective response meant to roll the seed away from the stimulus, which might prove fatal to the larvae inside.
Mexican jumping beans, Sebastiania pavoniana, is well known in America where the beans are sold as a novelty. It is parasitized by the jumping bean moth, Cydia deshaisiana. Another plant indigenous to Southern Africa known as the jumping bean tree (produces lovely ‘tambotie’ wood) is parasitized by a snout moth (Emporia melanobasis). When the seed matures and splits it causes the larvae to wriggle about inside and makes the beans ‘jump’ erratically.
- Schmutz, J. et al. A reference genome for common bean and genome-wide analysis of dual domestications. 2014. Nature Genetics. 46(7): 707-717
- Gepts, P. Origin and Evolution of Common Beans: Past Events and Recent Trends. 1998. HortScience. 33(7): 1124-1130
- Mamidi, S. Demographic factors shaped diversity in the two gene pools of wild common bean Phaseolus vulgaris L. 2013. Heredity. 110: 267-276