Blossoms And Bounty: A Comprehensive Guide To Purple Hyacinth Bean Care

The purple hyacinth bean plant (Dolichos lablab or Lablab purpurea) is a beautiful annual vine. Native to tropical African regions, it is also commonly called the tonga bean, Egyptian bean, or tobacco bean. While typically considered a flowering plant, most parts of purple hyacinth beans are also edible if cooked in a specific way. The leaves, stems, flowers, and seed pods all display varying shades of purple. These fabulous heirloom plants grow quickly and vigorously, making them a popular pick for covering spaces quickly. By flowering late in the season, they provide a burst of color when the rest of the plant life has started to go brown. 

In this post, we will share everything you need to know to grow purple hyacinth bean vine. From finding the perfect spot to watering frequency, we will share all the tips and tricks to help you grow this delight in your garden.

What Is Purple Hyacinth Bean

Purple Hyacinth Bean (Lablab purpureus), often referred to simply as hyacinth bean, Indian bean, and Egyptian bean, is a strikingly beautiful and versatile plant. Native to tropical and subtropical regions, it's renowned for its vibrant, deep purple blossoms that adorn climbing vines. Beyond its aesthetic charm, this plant offers more than meets the eye. Its edible pods and nutritious seeds make it a valuable food source in some cultures, while its ability to fix nitrogen enriches the soil. Whether grown for ornamental purposes or as a functional addition to gardens, the Purple Hyacinth Bean continues to captivate gardeners and nature enthusiasts with its unique blend of beauty and utility.

Purple Hyacinth Bean Plant Care

Growth Characteristics

Purple hyacinth bean plants have bright green, pointed leaflets of three leaves. The vibrant green of the top of the leaf contrasts with the purple tinge on the leaf's underside and the stems. The scentless purple hyacinth bean flower grows in pale purple or white clusters, resembling a sweet pea flower. After the flowers fade, the glossy purple seed pods follow and grow to the approximate size of a lima bean pod. The vine climbs by twining around structures rather than using aerial roots. Purple Hyacinth beans can get 10 to 15 feet high and need adequate support through trellising or fencing. 

Light Requirement

Purple hyacinth beans thrive in full sun, making them sun-loving plants. To flourish and produce their stunning purple blossoms and vibrant pods, they require at least 6-8 hours of direct sunlight daily. Adequate sunlight ensures robust growth and promotes the development of their striking features. When planted in a sunny location with well-draining soil, these beans will reward gardeners with their beauty and productivity. While they can tolerate partial shade, it's essential to prioritize sunlight to achieve the best results.

Soil Requirement

Purple hyacinth beans thrive in well-draining, moderately fertile soil. They prefer soil that is slightly acidic to neutral (pH 6.0-7.0). Amending the soil with organic matter like compost can improve its texture and fertility, aiding in robust growth. Good drainage is crucial, as stagnant water can lead to root rot. These beans are adaptable and can tolerate a range of soil types, but they excel in loamy soils.

To ensure optimal development, prepare the soil by loosening it to a depth of 6-8 inches and incorporate organic matter before planting. With the right soil conditions, Purple hyacinth bean vines will flourish and grace your garden with their vibrant presence.

Water Requirement

Purple hyacinth bean vines have moderate water requirements, striking a balance between drought tolerance and consistent moisture. It's essential to keep the soil evenly moist but not waterlogged.

When initially establishing the plants, provide regular watering to help their roots establish. Once they are established, reduce the watering frequency but ensure deep soaking when you do water, allowing the top inch of soil to dry between watering sessions. This helps prevent overwatering issues. While they can tolerate short dry spells, consistent moisture during the growing season ensures lush foliage and more prolific blooming, making these beans a resilient and adaptable addition to your garden.

Fertilizer

The vines grow so rapidly that it would be beneficial to give them extra food every month throughout the heat of summer. With a base of the loamy, composted soil mentioned above, add a dose of fertilizer low in nitrogen and high in phosphorus every four to five weeks. This will encourage blooming. If a vine has a low bloom performance, it is either not getting enough sun or given too much nitrogen. Any fertilizer that you choose needs to be low in nitrogen, and high-nitrogen supplements like fish emulsion and soy meal should be avoided. 

Temperature And Humidity

In USDA hardiness zones 10 to 11, purple hyacinth bean vines can become perennial. They may develop woody stems. While it's nice that they would return year after year, they tend to be short-lived perennials. The purple hyacinth is more commonly sold annually, although they will reseed if the pods are left over the winter. 

Thankfully, purple hyacinth bean vines are rarely prey to disease or pests. Butterflies will sometimes lay eggs, and the caterpillars will eat away at the leaves for a time. It's a short period, however, and butterflies come as a result. 

Pruning

Pruning Purple hyacinth bean vines is a valuable practice that can help maintain their health, appearance, and productivity. Regular pruning of the purple hyacinth bean vine is recommended to encourage bushier growth, control their sprawling vines, and stimulate flower and pod production. Start by removing dead or diseased foliage and flowers to prevent disease and pests.

Additionally, trimming the tips of overly long vines can help keep the plant in check and promote branching. Be cautious not to over-prune, as it may reduce flowering. Prune selectively, and remember that these beans are resilient and can recover from pruning well. Proper pruning can lead to healthier, more vigorous Purple Hyacinth Bean plants in your garden.

Pruning is essential for Purple hyacinth bean vine when cultivated as perennials in USDA hardiness zones 10 and higher. Over time, the plant can develop woody stems, which not only appear unsightly but can also become brittle and prone to breakage. At the onset of early spring, start by removing any dead or broken stems using pruning shears. This initial pruning helps eliminate damaged growth, promoting healthy regrowth.

Harvesting

In some parts of the world, purple hyacinth vines are a forage crop. When the pods are still small, similar to snow peas, they cook similarly to green beans. The leaves and flowers are also edible, but care needs to be taken if the mature beans are to be eaten. They have to cook in a particular way, or they can be quite toxic, with high levels of cyanogenic glucosides. This causes vomiting, convulsions, and trouble breathing. The bean pods are easily harvested for future seeds, however. The pods will grow in size and plumpness as the flower dies away, and the prime time to harvest them is just before the first frost. Leave the pods to dry, and they'll be easy to open and remove the seeds. 

Common Problems With Purple Hyacinth Bean

Pest Infestations

Various pests, such as aphids, spider mites, and bean beetles, can occasionally target Purple hyacinth bean vine. These insects can damage leaves, reducing the plant's vigor and overall health.

Regularly inspect the plants for signs of infestation, including discolored or distorted leaves. To manage pest problems, consider using natural solutions like insecticidal soap or neem oil, which are less harmful to beneficial insects and the environment. Alternatively, introducing natural predators like ladybugs can help control pest populations.

Furthermore, it serves as the host plant for longtail skipper butterflies, and their larvae may consume the leaves. Japanese beetles consider the flowers and leaves quite appetizing. An occasional nibble from one of these pests typically doesn't pose a significant threat to the plant. However, if you wish to discourage them, a homemade mixture of soap and water, when sprayed on the leaves, can be an effective deterrent.

Fungal Diseases

Purple hyacinth bean vines are susceptible to fungal diseases like powdery mildew and rust, especially in humid conditions. To prevent these issues, ensure adequate air circulation around the plants by providing proper spacing and avoiding overcrowding. Water the plants at the base, avoiding overhead watering, which can create a humid environment conducive to fungal growth. If fungal diseases do appear, use fungicides labeled for garden use to treat the affected plants according to the product's instructions.

Root Rot

Overly wet or poorly drained soil can lead to root rot, a fungal infection that affects the roots, causing the plant to wilt and decline. To prevent root rot, plant purple hyacinth bean vine in well-draining soil and avoid overwatering. Allow the top inch of soil to dry between watering sessions to maintain an ideal moisture balance for the plants.

Inadequate Flowering

Insufficient sunlight can result in reduced flowering and pod production. Purple hyacinth bean vine thrive in full sun and require at least 6-8 hours of direct sunlight daily. Ensure they are planted in a location with ample sunlight to encourage prolific flowering and fruiting.

Low Temperatures

Purple hyacinth beans are sensitive to cold temperatures and frost. Plant them outdoors after the danger of frost has passed and the soil has warmed up in the spring. In regions with extended periods of cold weather, consider growing them annually or bringing them indoors as potted plants during the winter months.

Invasive Growth

Purple hyacinth bean vines are vigorous climbers and can become invasive if left uncontrolled. To manage their growth, regular pruning is essential. Trim back excessive growth, especially if the plant overtakes nearby structures or other garden plants. This will help maintain the desired shape and size of the vine while preventing it from becoming invasive.

How To Grow Purple Hyacinth Bean From Seed Pods

While purple hyacinth bean vines can sometimes be found as seedlings in nurseries, they are usually grown directly from seed. The seeds must be soaked overnight before planting to encourage germination, as they are quite hard. After all danger of frost is passed, the seeds can be directly sowed. Must pass the chance of frost, as the seeds will not germinate in cold soil, and young plants can die. Some prefer, then, to start the seeds indoors for a month or more before planting outside.

Seeds should be planted an inch or two deep, six inches apart. Germination will occur in two to three weeks. You will see young leaves and shoots. The purple hyacinth bean vine will be full and leafy for most of the spring and summer before any blooms appear.

Help the purple hyacinth bean vine find support with a trellis or fencing or whatever you want them to cover, and they will train themselves to follow that structure for the remainder of the growing cycle. Otherwise, they will become a tangled mess on the ground. 

Types of Purple Hyacinth Bean

The purple hyacinth bean vine primarily comes in one main variety, but it does offer a range of cultivars with slight variations in color and growth characteristics. Here are some common cultivars of the purple hyacinth bean vine:

Lablab purpureus 'Ruby Moon hyacinth bean': This cultivar is known for its deep purple foliage, which contrasts beautifully with its bright pinkish-purple flowers. It's a popular choice for ornamental gardens.

Lablab purpureus 'Scarlet Star hyacinth bean': This cultivar features reddish-purple stems and striking bright red or scarlet flowers. It adds a bold splash of color to gardens and landscapes.

Lablab purpureus 'Albus hyacinth bean': While not purple in color, this cultivar is distinct for its white or cream-colored flowers. It offers a unique contrast to the more common purple varieties.

Lablab purpureus 'Rongai hyacinth bean': This cultivar is valued for its drought tolerance and vigorous growth. It produces abundant purple flowers and pods.

Lablab purpureus 'Highworth hyacinth bean': This cultivar is notable for its larger, showier flowers and vigorous climbing habit. It also boasts attractive dark purple foliage.

Is Purple Hyacinth Bean Toxic To Pet

Yes, purple hyacinth beans can be toxic to pets, including dogs and cats, especially if they ingest dried beans, young pods, or any part of the plant. The beans and other parts of the purple hyacinth bean vine contain compounds like lectins and protease inhibitors that can be harmful when consumed. Ingestion of these substances may lead to gastrointestinal upset, including symptoms like vomiting, diarrhea, and abdominal pain in pets. In severe cases, it can cause more serious health issues.