Hyacinth bean

Hyacinth bean: how do you recognise it?

Habit

Annual twining climber 2–3 m tall and about 50 cm wide; the stems are often tinged purple.

Leaves

Trifoliate: three heart-shaped to triangular leaflets of 8–15 cm, green, often with a purple tinge.

Flowers

Pea-like flowers in upright clusters, pink to purple (also white). July–October.

Pods

Flat, curved, glossy purple pods of 5–8 cm with a few seeds.

Roots

Deep taproot with nodules that fix nitrogen from the air.

Flowering: July–October · Sowing: April–June · Plants: May–June

Why grow it?

• Fast annual climber: 2–3 m tall in a single summer.
• Ornamental on three levels: purple stems, pink to purple flower clusters (July–October) and glossy purple pods.
• Bees and bumblebees visit the flowers.
• Lovely on a wigwam or obelisk in the border or vegetable patch.
• Easy to sow and easy to look after.

Hyacinth bean: where does it grow best?

• Full sun in a warm, sheltered spot, for example in front of a south or west wall.
• Ordinary, free-draining garden soil: sand, loam or clay, acid to chalky.
• Normal moisture: water evenly without waterlogging.
• Give it a support of 2–3 m: an obelisk, a wigwam of bamboo canes, a net or a fence.
• Plant 25–30 cm apart; it also suits a large pot of at least 30 cm.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

3 m tall, 0.5 m wide

Hardiness

Frost tender: overwinter indoors (above 5 °C)

Goes well with

• Zinnia: Colourful annual for the same sunny spot.
• Cosmos: Airy, flowers for a long time and also attracts bees.
• French marigold (Tagetes): A compact yellow or orange edge at the foot of the support.
• Climbing nasturtium: Another annual climber with flowers in fiery colours.

Hyacinth bean: when and how to plant it?

Plant in May–June.

1. Soak the seeds overnight in lukewarm water.
2. Sow indoors in April, 2–3 cm deep, in 8–9 cm pots at 18–24 °C; they germinate in 1–2 weeks.
3. Or sow outdoors in late May–June, 2–3 cm deep, when the soil is warm and night frost is over.
4. Harden off plants sown indoors and plant them out in late May–June.
5. Plant 25–30 cm apart by a support and water straight away.
6. Spread a layer of mulch round the base and protect young plants from slugs.

Care

Water

Keep evenly moist, especially during flowering and pod formation; water generously in dry spells.

Feeding

Little needed: a little compost at planting is enough. Too much nitrogen gives plenty of leaves and few flowers.

Support

Guide young shoots to the support; after that it twines by itself.

Pods

Let a few pods ripen for seed; remove the rest if you want a longer flowering season.

Tip: Beans do not like being transplanted: sow it straight where it is to grow, next to a support, as soon as the soil is warm. In the sunniest spot the pods turn the loveliest purple.

Hyacinth bean: when to prune it?

When: It is annual and is not pruned. Only trim overlong or damaged stems.

How:

• Lead long stems back to the support or cut off the ends.
• Remove faded flower clusters if you do not want seed.
• Leave a few pods to ripen on the plant for seed.
• Remove the dead plant after the first frost.

Pruning calendar and basic rules

Propagation

Seed

April indoors or May–June outdoors: soak the seeds overnight and sow them 2–3 cm deep at a minimum of 18 °C. They germinate in 1–2 weeks.

Collecting seed

In September–October let a few pods turn brown and papery on the plant. Collect the seeds, let them dry and store them cool and dark for next year.

Hyacinth bean: how does it get through the winter?

Hardy to 5 °C: protect in harsh winters.

• Not hardy: it dies in frost and dislikes temperatures below about 5 °C. Treat it as an annual.
• Remove the dead plants after the first frost; they can go on the compost heap.
• Store seed dry, cool and dark until next year.

Diseases and pests

• Aphids: On young tips and flower clusters in summer. Spray off with water or let ladybirds do the work.
• Slugs: Young plants are eaten in May and June. A collar round the plant helps, and collect slugs in the evening.
• Weak or late flowering: A cool summer, too little sun or too much nitrogen. Put it in a sunny, warm spot and do not over-feed.
• Seeds do not germinate or rot: Soil too cold and wet. Sow outdoors only when the soil is warm, or sow indoors.

Through the year

• January: Rest. Get seed and support ready.
• February: Plan. Repair the support.
• March: Prepare the soil. Get pots and compost ready.
• April: Sow indoors. Soak the seeds overnight first.
• May: Harden off. Sow or plant out outdoors in late May.
• June: Sow or plant out outdoors. Set up the support. Water.
• July: First flowers. Water.
• August: Flowers and pods. Water.
• September: Full flower and pods. Let seed ripen.
• October: Flowering until the first frost. Collect seed.
• November: Clear away dead plants.
• December: Rest. Store seed dry.

Edible and useful

Not edible. The glossy purple pods and beans of the hyacinth bean look like those of climbing French beans or runner beans. In the tropics they are eaten after long cooking, but raw or undercooked they are poisonous, to people and animals alike. Grow it here as an ornamental, do not eat any of it and do not put it among the beans in the vegetable garden, so that nobody picks them together. Keep children and pets away from the pods and seeds. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• In the tropics the plant is grown as a food and fodder crop; raw, it is poisonous.
• Thomas Jefferson already grew the hyacinth bean in his garden at Monticello.
• As a legume it lives with nitrogen-fixing bacteria in nodules on its roots.