Vigna Unguiculata subsp. sesquipedalis
Sitaw, Juro Kusasagemae, Chang Dou, Tao Fug Yao, Dau Dua,
A member of the Vigna genus, whose members also include adzuki beans (V. Angularis), mung bean (V. Radiata) and black gram (V. Mungo), the long bean is a subspecies of cowpea. Vigna is a widely distributed genus, with over 80 species distributed through various tropical and sub-tropical areas.There are 7 distinct domesticated species, 5 of whom are Asiatic in origin, 2 are African With multiple centers of domestication, it's believed that cowpeas originated in various parts of Africa, where they have been cultivated since the second millennium BCE. It is believed that there was a second domestication period in 2300 BC in parts of South Asia where varieties developed distinct morphological characteristics. The long bean is of the South and Southeast Asian domesticated subspecies.
Long Beans are widely distributed throughout Asia, where they have been embraced by so many cultures. The beans are not only delicious and versatile, but are highly nutritious. They are also incredibly vigorous growers, who can reliably fruit throughout the season, and whose fertility and water demands are low.
When to plant:
They are grown as an annual and have an indeterminate growth habit. They are not cold hardy and thrive in the heat. Direct seed anytime after the threat of frost has passed, when daytime temperatures are 65 degrees consistently. In central California, we plant our first succession at the end of April, though mid-May plantings can easily catch up to earlier ones once the soil has really warmed. In temperate climates, you can plant anytime between May and July.
For best germination, we recommend pre-watering your planting area and direct seeding into moisture. Some growers recommend flame weeding or making a quick pass with a hoe to eliminate the weeds that come up following the irrigation. Plant the seed about an inch deep and cover with soil. At this point, stop watering and wait for emergence. When they germinate, give them about 12" between plants.
In this picture you can see that our first true leaf has developed. Long Beans have the classic trifoliate leaf similar to other cowpeas. At this point, test soil moisture and begin supplementing irrigation. Now the plant has started to photosynthesize, and additional moisture will promote vigorous growth. They don't need a lot of watering though! These guys have a somewhat waxy exterior which probably helps inhibit too much transpiration in the heat. Always judge moisture by observing the plant in the mornings. By midday, the leaves may droop a little in order to shut down their stomata and prevent water loss. But this does not indicate the need to water. If the plants look perked up by the end of the day, they are ok. In our climate where summer temperatures average between 95-106 degrees, we water once a week, to once every 12 days or so for about 45 minutes on low flow drip. If your soil is lower in organic matter or does not retain water as well, once a week deep watering is recommended. Excessive watering may cause low fruit set, as flowers are known to drop when the plants' feet are too wet. It can also lead to pest or disease vulnerability. These crops have been so invaluable to many communities distinctly because they are strong and resilient, so it's best to keep selecting our plants in that direction.
It's recommended to trellis these plants, as they produce prodigious amounts of vegetative growth once things really heat up, and their vines will seek support. Remarkably, once the plants are flowering, they will orient their racemes upward to find air and light even if left to sprawl on the ground, so if you can't trellis, they will still produce a good amount of beans. The trellis will create ideal conditions for maximum flowering and will make harvesting much easier. The plants are quite bushy, in addition to sending vines in any given direction. They grow wide as well as tall so consider a trellising style that will provide vertical space, while also being able to support some weight.
So summer is moving along, and your plants are starting to flower. The raceme produces two to three flowers at each tip, which will mature into beans. You can see the young beans developing in the picture above. Something to note, is that at each tip, there is an additional bud waiting to lengthen for more flowering. Once you harvest the beans on any given raceme, it will produce more growth and continue to fruit so long as you don't injure those buds as you harvest.
When it comes time to harvest, depending on your taste, or that of your community, you may prefer beans at different stages of maturity. When they have grown to be between 12-18" and are relatively thin before any amount of bean formation inside the pod, you can begin to harvest.
Here you can see a bean that will be super crunchy and tender. Folks tend to prefer this when using the beans raw.
With these pods, you can begin to see the formation of the bean within. At this stage, folks prefer them for simmering in sauces or sautéing. When the beans begin to form, the inside becomes a little spongy or pithy, which is great for absorbing flavor from oils or sauces.
Although they are indeterminate and are capable of producing beans throughout your whole season, succession planting can help with maintaining consistency in harvest and quality. As plants age, some varieties will have a tendency to try to mature beans more rapidly. So you end up with shorter beans trying to make mature seed. Our favorite variety is Red Noodle, both because it's strikingly beautiful, but also because the harvest window is longer, beans mature less rapidly and the plants produce super reliably.
Be warned, for best quality you will need to harvest every other day!
It's best to reserve a few plants as your seed producers. As the plants are growing, see if you notice any particular specialness within your population. Are some plants particularly hardy? Do some show less sign of drought stress? Choose a couple plants who you will let growth undisturbed, and who will mature beans earlier. The rest of the plants can be harvested for food. There are a few reasons for this. One is that the first rounds of beans can create the highest quality seed. The plant has grown and is channeling all its energy into creating viable seed. Another is that if you leave seed saving for the end of the season, the plants may be more tired by then, and as we mentioned before, in more of a hurry to make a seed. You may end up accidentally selecting for smaller pods, or more rapid seed development which are somewhat undesirable traits for production. You can be more deliberate and clear with your selection criteria, and beyond germination rate, have seed that display a wide range of positive long term health.
We look for both the health of the plant itself, and pods that have the qualities we are looking to perpetuate (color, size). The pods take several weeks to fully ripen, and as much as possible, you want the bean to mature and dry on the plant. These beans are not terribly prone to shattering, so it's not too much of a gamble to leave them on the plant as long as your season permits. Pest sedation may be the biggest factor. If you have small mammals or turkeys eating your beans, you can harvest beans once you can see the seed inside has sized up and the pod begins to dull to a matte color. They can finish drying down in a protected area and then shelled once the pods are brittle.
Here are our beans being harvested for seed collection. At this stage ,the pods are not really pliable, and where they meet the raceme is dry.
Store the beans in a cool dry place. As many beans can be subject to weevil predation, we pack our seed stock in 2# increments so if there is a potential weevil problem in one bag, we don't endanger the whole lot. We store them in hermetically sealed bags which limits the risk as well.
In short, specs for growing yard long beans:
Sun: Full to partial. Most important, these guys love heat
Moisture: Low. Once a week or less during vegetative growth. Once a week during fruiting to optimize yield.