How to Plant, Grow, and Care For ‘Ruby Moon’ Hyacinth Beans

The hyacinth bean is an easy-going, vigorous flowering vine with excellent ornamental value. It’s also edible if prepared properly, though the mature beans are toxic if eaten raw. Its gorgeous foliage and sweet-smelling flowers make this a worthwhile addition to any garden. 

This intriguing vine prefers tropical climates and is a perennial in zones 10-12. Elsewhere, it’s easy to grow as an annual, and commonly self-sows, returning the following spring. Its fast-growing, twining habit makes this an excellent choice for any trellis. 

Ruby Moon Hyacinth Bean Seeds

Grown by Thomas Jefferson at Monticello, hyacinth bean is a dazzling ornamental with stunning, pinkish-purple flowers and shiny, dark purple pods that stand out against the purple and green foliage.

Twining stems quickly climb a fence or trellis, trail across the ground for an attractive ground cover, or spill over container edges. Contains toxins; not recommended for eating. 

Buy at Botanical Interests Shop

‘Ruby Moon’ Hyacinth Bean Overview

Plant Type Annual or perennial Family Fabaceae Genus Lablab Species Purpureus	Native Area Africa and India Exposure Full sun Height 10’-20’ Watering Requirements Low to Moderate	Pests & Diseases Japanese beetles, caterpillars, aphids, rust, blight, fusarium wilt Maintenance Low Soil Type Clay, Loam, Sand, Chalk Hardiness Zone 10-12

What Is It?

‘Ruby Moon’ is the most popular hyacinth bean variety, and with good reason. It’s a robust cultivar with an extra helping of all of the species’ best qualities. It’s incredibly easy to grow and requires minimal care in exchange for a substantial payout. It’s one of my personal favorites that I planted once, and it’s stuck around for years!

Characteristics

‘Ruby Moon’ hyacinth bean is a stunning plant with a vining habit. The pretty, purple stems are excellent at twining around any nearby structure. With support, this vine will grow up to 20 feet. It branches bountifully and forms a lush, luxuriant mound of violet-hued foliage. 

The leaves, which share a purple tint with the rest of the plant, are large, soft, and heart-shaped. They start out light green and gradually age to a dusky, dark green with a violet overtone. 

The flower spikes are long and elegant, featuring blue-violet, pea-like blossoms with a sweet, pleasant fragrance. They make excellent cut flowers. When the flowers fall, deep plum colored pods develop in their place. Hyacinth bean offers ornamental value from late summer until the first frost. 

Native Area

The hyacinth bean is native to tropical Africa and India. It’s particularly common in eastern Africa, including Ethiopia. Its history of cultivation goes back a long way in Southeast Asia. There, locals grow it as both a stunning ornamental plant and a traditional food crop.  

Planting

‘Ruby Moon’ hyacinth bean is frost sensitive, and takes a while to mature as an annual. Depending on your climate, you can directly sow the seeds as soon as the threat of frost has passed, or start them indoors. For cooler climates, start seeds a month to 6 weeks before the last frost date. 

They grow best in warm soil, so if you directly sow them, be patient. Mine self sow, and it takes until about the end of June for them to sprout. Moisture will aid in germination. 

Transplanting

Harden off your seedlings in the week leading up to transplanting. Choose a cloudy day or plant in the morning to reduce heat stress. I find these incredibly easy to transplant. They pop up here and there, and I simply dig them up and move them to where I want them. 

Keep the soil moist for a week or so to help the roots acclimate. After that, this plant should require minimal care, unless you need to trim it back. You can mulch around the base to help the soil retain moisture if you like. 

Growing From Seed

If you want to get an early start in a cooler climate, start your seeds indoors, about six to eight weeks ahead. These are large seeds that don’t require light to germinate, so direct sowing is the preferred method for those in mild climates. 

The seeds have a thick outer covering, so scarifying and soaking them will expedite germination. Soak your seeds for 8 to 12 hours before sowing, and then nick the seed coat with a knife or small tool. Do not sow if the weather is hot. The seedlings will decline before growth can occur. Instead, sow when temperatures are between 65 and 85°F (18-29°C).

Plant your seeds about one inch deep and 12 inches apart. They require a trellis or other structure to climb, and once they get started, they grow rapidly. Keep the soil moist during germination, and then reduce watering to a moderate level. Once established, they are fairly drought-tolerant.

How to Grow

In cooler climates, these can be more challenging as they take a considerable amount of time to bloom. Gardeners with a short growing season may struggle with them unless they start the seeds ahead of time. In general, these plants are nearly carefree and make a big impact.

Light

For the best growth and bloom, plant your ‘Ruby Moon’ hyacinth bean plants in full sun. They will flower best in a spot with six to eight hours of sun daily. In partial shade, they will grow, but more slowly. They also won’t flower as well, and the vines and stems may be weaker. 

Water

These vines need a moderate amount of water. When first planted, make sure the soil remains moist while the plants establish strong roots. Once established, you can water approximately once a week, depending on the weather conditions. Moderate rainfall is typically sufficient. 

Once it matures, ‘Ruby Moon’ is relatively drought-tolerant. However, giving it consistent water will help produce more and stronger flowers. Avoid overwatering, as soggy soil can cause root rot. 

Soil

In terms of soil, hyacinth bean is adaptable. It will grow well in any type of soil, including poor, sandy soil. If you have this type of soil, it won’t hurt to amend it with some compost ahead of planting. Overly nitrogen-rich soil will lead to an abundance of green growth and fewer flowers. 

Drainage is the most critical soil factor; therefore, heavy clay soil can be tricky, but not impossible. Amending with looser materials, such as compost, sand, or perlite, will help improve drainage. Slightly acidic soil is ideal. 

Temperature and Humidity

Hyacinth bean is frost sensitive and not hardy north of zone 10. It will die off with even a light frost. It prefers warm weather and tolerates heat well once established. The optimal range for vigorous growth is between 70 and 85°F (21-29°C). 

These vines will tolerate a range of humidity levels. However, they are native to tropical climates. They are happiest in moderate to high humidity. In climates with high humidity, ensure good air circulation to avoid powdery mildew. 

Fertilizing

In fertile soil, don’t worry about fertilizing ‘Ruby Moon.’ Too much nitrogen can be detrimental in this case. It will cause an abundance of leafy growth, but at the expense of flowers. If you have poor soil, a single application of a balanced fertilizer, early in the season, is best. Hyacinth bean is a legume, and therefore, a nitrogen fixer. 

Maintenance

As an annual, hyacinth bean requires no substantial maintenance. Deadheading the flowers can help produce more and also reduce self-sowing. These plants re-seed freely, so it’s a good idea to remove the seed pods. If it grows too large for your support, it tolerates cutting back. 

Propagation

While it’s possible to propagate hyacinth bean with cuttings, it’s far easier to grow them from seeds. The seeds will germinate and develop as quickly as a cutting forms roots and begins to grow. So, it’s not worth the extra work for most gardeners.  

Common Problems

‘Ruby Moon’ hyacinth bean is a sturdy plant with few issues. There are a few pests and some fungal diseases to look out for. Even these are uncommon. 

Pests

Aphids are common garden pests that are opportunistic. There are many types, and there are few plants that they won’t feed on. You’ll see aphids show up as clusters of soft-bodied insects. They primarily appear on tender, new growth. 

Aphids can cause stunted and misshapen growth, as well as leave behind a sweet, sticky excrement. This substance, known as honeydew, can also pose a problem. It hosts sooty mold, which can interfere with photosynthesis. Blast them with a strong stream of water from a hose. Follow up with neem oil and insecticidal soaps to help eradicate them if water doesn’t do the trick. 

Japanese beetles are another potential problem for this vine. They eat the leaf tissue, skeletonizing leaves and chewing on flowers, as well. Beetle traps are often effective in combating them. Neem oil works, too. Handpicking them in the morning is the most effective method of removal. 

Caterpillars occasionally feed on the foliage of this plant. Signs include chewed leaves and droppings left behind. Handpicking is typically the most effective treatment for caterpillars. 

Diseases

Hyacinth bean has few disease issues, but in humid climates, fungal issues can arise. Maintaining good airflow will substantially minimize the occurrence of these issues. Watering at the soil level, rather than overhead, also minimizes the risk of fungus.

Powdery mildew is the most common fungal disease you may run into. Sulfur-based fungicides work best at eradicating it, but improved air flow is important. Otherwise, it will likely return. 

Rust is a more serious fungal disease that appears as small, orange pustules on leaves. It’s not common on this plant, but it can happen. Remove any affected foliage as soon as possible and dispose of it properly. 

Root rot can occur as a result of overwatering or poor drainage. Make sure to plant in well-draining soil, and water moderately. In times of regular rainfall, you will rarely need to supplement. 

Frequently Asked Questions