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Winged Bean Plant Care: Growing Dragon Beans

The winged bean (Psophocarpus tetragonolobus) goes by multiple names such as dragon bean, princess bean, goa beans, asparagus pea, four-sided beans, Hunan winged bean, four-cornered bean, and many more! The winged beans are native to Southeast Asia and thrive in tropical climates since they require a long growing season. There are, however, day-neutral varieties that are suitable for growing in a temperate area. 

Winged beans grow on vines and will need a structure to support the climbing stems. Provide these beans with a trellis on the north side of your garden and you’ll be picking beans into late summer. The blue flower it produces will attract many beneficial insects and pollinators. As its most common name suggests, the bean pods have four frilly wings that run the length of the bean. 

These unusual winged bean plants are quickly gaining popularity amongst gardeners and for good reason. If you are interested in growing your own food this plant is an especially interesting choice because the entire plant is edible, even the tuber! The mature bean is a rich protein source and has more protein than similar beans such as cowpeas, chickpeas, mung beans, etc. It has a similar protein content to soybeans and can be used in many of the same ways. 

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Quick Care Guide

Winged bean
The winged bean is uncommon in the US but gaining popularity. Source: eric.toensmeier
Common Name(s)Winged bean, dragon bean, four-angled bean
Scientific NamePsophocarpus tetragonolobus
Days to Harvest75-80 days
LightFull sun
WaterModerate
SoilWell-drained, fertile
FertilizerCompost or balanced fertilizer
PestsAphids
DiseasesDowny mildew, aphid-borne viruses

All About The Winged Bean

Single winged bean
The distinctive shape of these beans makes them stand out. Source: asirap

As mentioned above, winged beans (Psophocarpus tetragonolobus) are known by multiple names including four-cornered bean, Hunan winged bean, cigarillas, manila bean, four-angled beans, and goa bean. They are native to South Asia and are thought to have originated in New Guinea. The common garden winged bean is grown as a perennial in tropical climates, but can also be grown as an annual in most of the United States. 

The winged bean pod resembles a broad bean with four ruffled wings that run the length of the pods. Inside, the winged bean seeds are hidden away, although most harvest the pods before they produce mature seeds. The leaves appear similar to those of string bean plants and the bright blue flowers produced look like pale blue versions of the snap pea flower. The tubers bear a striking resemblance to sunchokes. Winged bean is a pole bean and as such grows as a vine. These plants are not only used as food for people but are also used as feed for fisheries and for livestock because of their high protein content. 

Planting Winged Beans

Winged beans are especially frost-sensitive so it’s best to wait until all threat of the last frost for the season has passed before transplanting any seedlings. They can be started indoors and transplanted into raised beds or sown directly into containers and then moved outside once any cool weather has passed. You can also simply start them in the ground that they’ll grow in, provided that the threat of frost has passed and the ground is warm enough to aid in germination. They need full sun and a structure like a trellis to support the climbing vines. The dried seeds can be pre-soaked to hasten germination. Once the seed sprouts from the ground, monitor and direct its young vine tendrils toward its trellis so it can begin to climb.

Care

Winged bean flower
The winged bean’s flower is as distinctive as the bean itself. Source: rwsphoto

Caring for the winged bean is similar to caring for any other pole bean variety, just with the added benefit of being able to eat all parts of the plant. Winged bean vines will need something to grow on and the roots may reward your garden efforts by fixing nitrogen into the soil.

Sun and Temperature

Winged beans require full sun. For those of us in the northern hemisphere, that means placing these pole beans on a trellis on the north side of your garden so that they don’t potentially shade out other plants. The native winged bean varieties that establish themselves in the tropics wait for the heat of summer before putting on measurable growth, then await the signal of the shortened days of fall before flower set and putting out pods. In a temperate climate, these varieties will never get the chance to mature, because the shortened days of fall also come with temps that are too cold for these plants to survive. 

When growing winged bean as an annual in a temperate climate, it’s important to select a day-length neutral variety. These winged bean varieties will set flower much sooner and don’t rely on the signal from shortened days to bloom. This ensures that they will produce winged bean pods sooner than their non-day-length neutral relatives.

The winged beans that are native to Southeast Asia can be grown in USDA growing zones 9-11 and have been reported to grow like weeds in those climates. The day-neutral varieties can be grown in all other zones, but in cooler climates may need to be started indoors and transplanted out. These plants will need at least a 120 day long growing season. Consult your local frost dates to determine the right planting time for your region. 

Water and Humidity

As with most plants grown in the heat of the summer, it’s best to water your winged bean in the morning so that the moisture has a chance to absorb into the soil before the heat of the day. Since winged beans are specialized to survive in the warm and wet tropics, they require even moisture and regular watering. They do not tolerate periods of drought well and really prefer a little humidity. This makes them a surprisingly good choice for southeastern US growers.

Winged bean seeds also require plenty of moisture in order to germinate. To aid in germination, it’s best to soak the seeds for 24-48 hours before planting out. This step can be skipped, but it may take them up to 3 weeks to germinate without it. 

Soil

Winged beans do best in an average, neutral ph soil. They can survive in multiple soil types such as clay, silt, or loam soil. In addition, winged bean will need well-draining soil to ensure that the tubers do not rot before they can be harvested and eaten, so ensuring your soil blend is organic-rich will help.  

Fertilizing

Your winged bean plants prefer soil amended with plenty of organic matter via quality compost. It does not require a nitrogen-rich fertilizer. If it receives too much nitrogen, it will put on a lot of leaves and vines, but will not produce many blossoms or winged bean seed pods. Beans and other legumes, with winged bean among them, are well known for their ability to fix nitrogen into the soil. This makes them a great crop to rotate into an area of your garden that may need a boost or to companion plant with a crop that loves nitrogen. Having said that, phosphorus and potassium are both beneficial for the winged bean, particularly phosphorus as it aids in flowering.

Pruning

Winged beans do not require any pruning, but cutting back the tops of the vines once they reach about 12 inches in height can encourage bushier growth. Harvesting the leaves for food can be an excellent way of pruning without actually pruning. If the vines appear to be growing wild and out of control, some pruning may be necessary to increase airflow and prevent potential disease issues. 

Propagation

There are no known methods of propagation for the winged bean plants other than starting from mature seeds. As mentioned above, soaking the seed for 24-48 before planting will help hasten germination. This step is not necessary but will help get a head start on your plants. Since the seeds have such a thick wall, soaking helps to soften them and they will sprout sooner. 

Generally speaking, winged bean seedlings do not like root disturbance during transplant, so take care when transplanting out or try sowing directly when possible. 

Harvesting and Storing

Harvested winged beans
Once picked, winged beans are an incredible addition to your meals. Source: Thai Food Blog

The winged bean plant makes a great addition to any vegetable garden because all parts of the plant are edible, even the tuber! These tropical legumes have a great taste and nutty flavor. 

Harvesting

The protein-rich pods are ready to harvest when they are bright green, tender, and still flexible, about 2 weeks after blossoms appear. Young green pods, like snap peas, can be eaten raw pod and all. Once the pods become tough and fibrous, then they are harvested for the seeds inside, which require a 2-3 hour cooking process to make them digestible. 

The young leaves can be used as you would use spinach: in salads, steamed, or added to soups, stews, or rice dishes. The pale blue flowers can be harvested once they are fully opened and make a beautiful garnish. 

While the pods, leaves, and flowers are ready to pick within about 75-80 days, their roots won’t be ready until about 120 days. At the end of the season, dig up the plant to reveal the tuberous roots. They can be used similarly to potatoes and can be boiled, steamed, baked, fried, or made into chips.

Storing

The immature pods should be treated similarly to string beans in that they have a string to remove from each of the four angles of the bean. Once the string is removed it can be used fresh in stir-fries, steamed, eaten raw, or blanched, and then frozen for future use. Pickling the young pods is another option for extending the shelf life of this bean. If the pods are left to fully mature then it’s best to discard the tough fibrous pod and process the seeds. They can be dried and stored for future use or saved as seeds for the following growing season.

Your winged beans themselves can be stored in the refrigerator for up to a week in a plastic bag. The flowers and leaves should be used fresh.

Troubleshooting

Young four-angled bean plant
The four-angled shape of this bean’s pod makes it unusual. Source: foot fingers

Winged beans are a great low-maintenance addition to every vegetable garden since they have few pests and even fewer disease issues. Especially in zones 9-11, they are known to grow like a weed once established. 

Growing Problems

Winged beans do not tolerate drought conditions. However, overwatering can cause issues as well. Root rot can occur when this plant is overwatered or placed in soil with poor drainage. If you wish to collect your tubers at the end of the season, then it is especially important to transplant winged beans into loose, well-drained soil to allow the tubers to develop fully. 

Yellow or brown droopy leaves on the winged bean vine are a sign of overwatering, while dry brown crunchy leaves are a sign of underwatering. 

Pests

Aphids are the most common issues for winged beans and bean vines in general. While these are not necessarily a bad sign, an aphid infestation that’s allowed to go unchecked increases the threat of aphid-borne viruses, such as bean mosaic virus. The majority of plant viruses are spread by insects, and if an aphid feeds on an infected plant, it may move on to a healthy plant and then spread the disease further.

Some beneficial insects such as ladybugs and lacewings will happily consume aphids, especially if you provide them with good habitat and overwintering sites. Still, aphids multiply at a rapid rate, and a single female aphid can produce up to 80 live-birthed young in the space of a week. If you see aphids beginning to appear, use a blast of water to knock them off the plant. Those that keep popping up can be handled with insecticidal soap, neem oil, or by removing the most infested leaves and disposing of them entirely.

Diseases

Overwatering can cause the perfect conditions for fungus to take hold, especially in humid climates. If too much moisture splashes onto the foliage during watering then this can contribute to issues with downy mildew. 

Downy mildew is often mistaken for powdery mildew but it appears as yellow leaf spots on the tops of the leaves with black spore masses on the underside of the leaves. In contrast, powdery mildew appears as more of a white flour-like powder on the leaves.

To prevent these issues, always bottom water your plants. Neem oil may also be sprayed as a preventative measure to reduce the colonization of spores on foliage. In advanced cases of downy mildew, it may be best to remove and destroy infected material to prevent it from spreading to nearby healthy plants. After removing infected material, spray neem oil or a liquid copper fungicide onto the remainder of the plant and nearby plants to reduce the risk of further spread.

Frequently Asked Questions

Dragon bean leaves
The leaves of the dragon bean are lush and almost heart-shaped. Source: Puddin Tain

Q: Can you eat winged beans?

A: Yes, the entire winged bean plant is edible including the pods, seeds leaves, flowers, and tubers. 

Q: What is winged bean good for?

A: The immature pods are delicious when blanched and served in a stir fry. They can be eaten sauteed, steamed, roasted, grilled, or fried in a tempura batter. In addition, winged bean is often used as a fodder for livestock. Seeds can be stored and planted in subsequent years, making it an easily-renewable fodder source.

Q: Are winged beans poisonous?

A: No. However, mature seeds must be cooked for 2-3 hours to destroy the trypsin inhibitor and hemagglutinins that inhibit digestion. Tubers can be cooked in this manner as well or eaten raw. Immature young pods and the winged bean flowers do not require this lengthy cooking process and can be eaten fresh off the plant as raw crisp beans, or can be lightly steamed.


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