Ornamental · Fabaceae
Hyacinth Bean
Lablab purpureus
Give it heat, full sun, and a tall trellis, and hyacinth bean throws purple flowers and glossy pods clear into fall.
Full sun
Every 5–7 days
50–95°F · 10–35°C
90–120 days
Overview
Hyacinth bean is a fast climbing vine that's all about the show, sending up spikes of purple or white flowers that turn into glossy reddish-purple pods holding their color right up to frost. It's part of the pea and bean family, and in warm places it'll live for years, but most folks just run it as a summer annual from seed. Give it a tall trellis and it'll climb well past head height in a single season, so it doesn't take long to make a statement.
Honestly, the looks are the whole reason to grow it. The pods are every bit as pretty as the flowers, and few things you can sow will cover an arbor or fence this fast. And because it loves heat, it keeps rolling through the dog days when a lot of other climbers just stall out.
There's one thing that separates it from a regular garden bean, and it's worth knowing. The raw mature seeds and pods carry cyanogenic compounds and are toxic eaten raw, safe only once they're cooked well, so think of this as a plant for your eyes more than your dinner plate.
Care
The short version: full sun and plenty of warmth, light well-drained soil kept evenly moist while it's getting going, a balanced feed that goes easy on the nitrogen, and a sturdy trellis to hold up all that fast, heavy growth.
Light
Hyacinth bean wants full sun, ideally 6 or more hours a day, so it can flower well and keep that pod color. A little afternoon shade is fine, but too much shade and you'll get leggy growth instead of blooms.
Water
Keep the soil evenly moist while the vine is settling in, then you can back off, since an established plant handles a bit of drought. Water deeply when it's hot and dry, and go for light, well-drained ground rather than anything soggy.
Soil
Average, fertile, well-drained loam works just fine, with a pH anywhere from 6.0 to 7.5. It isn't picky about richness, so good drainage counts for a lot more than piling on the feed.
Temperature
This one's a heat lover that does best between 50°F and 95°F (10°C to 35°C) and stalls once it turns cool. Frost kills it flat out, so it only goes outside once the cold's done for the year.
Humidity
Regular outdoor humidity is plenty, so there's nothing to chase here. What really helps is good airflow, because crowded, damp leaves are what bring on leaf spot.
Feeding
Feed it monthly through summer with a balanced fertilizer. It's a legume, so it makes its own nitrogen, which means you should go light on high-nitrogen feeds that push leaves instead of flowers.
Pruning
Pinch the growing tips early to get the vine branching, and after that it barely needs a trim. Remove spent pods to keep the flowers coming, then cut the frost-killed vine back once the season's over.
Repotting
not typically grown in containers; grown as an annual from seed each year
Size & spacing
Count on a fast climber that hits 10 to 20 feet (3 to 6 m) tall and spreads 3 to 6 feet (91 to 183 cm) wide. Give it a sturdy trellis or arbor and room to stretch out so all that heavy growth has something solid to grab.
When to plant
Hyacinth bean lives on heat and packs it in at the first frost. Sow it outside only once the cold's gone and the soil's warmed up, or start it indoors 6 to 8 weeks ahead for a head start, and it'll flower from summer right up to fall frost.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6 to 8 weeks before the last spring frost
- Plant: after danger of frost has passed and soil is warm
- Harvest: summer to frost (roughly June until first fall frost)
Hardiness
USDA hardiness zones: 10–11
Temperature: down to -1°C
Troubleshooting
Hyacinth bean is a tough customer that shrugs off most trouble, and when something does crop up, it's usually a pest rather than a disease. Keep an eye on the leaves and new growth for the early signs below, and jump on it before a small thing spreads down the vine.
Speckly, yellowing leaves with a bit of webbing
Hot, dry stretch got the leaves looking dusty and pale? That points to spider mites. Tap a leaf over a sheet of white paper and watch for tiny specks moving around, then check the undersides for faint webbing. Hose the whole vine down to knock them loose and bump up the humidity, and if a few stick around, insecticidal soap or horticultural oil takes care of them.
Fix:
- Hose down foliage to dislodge mites and raise humidity
- Apply insecticidal soap or horticultural oil if infestation persists
Short vines and hardly any flowers when it's cool
Hyacinth bean is all about heat, so cool weather leaves it dragging its feet with stubby vines and barely any bloom. You'll see the same thing if the seedlings go out before the ground warms up and frost is truly done. Give it warm soil and a cozy, sunny spot, and it'll shoot up the second the temperatures climb.
Fix:
- Wait to plant until soil is warm and frost danger has passed
- Provide a full-sun, sheltered, warm site
Leaves chewed into a lacy, see-through pattern
Leaves that look like lace? That's usually Japanese beetles, and they turn up most in summer when the shiny green-and-copper bugs pile onto the vine. They eat the soft stuff between the veins and leave the skeleton behind. Just pick them off by hand early in the morning, and don't sweat a little damage, because a vine this quick grows right back.
Fix:
- Hand-pick beetles in early morning and drop them into soapy water
- Tolerate light damage, since vines push out fresh foliage and survive well
New growth that's curled up and sticky
When the fresh shoots and buds curl up and feel tacky, that's almost always aphids. Peek under the young leaves and you'll spot little green or black clusters, plus the shiny honeydew they leave behind. A good blast of water usually clears them out, and insecticidal soap is there for the times a colony really digs in.
Fix:
- Spray colonies off with a strong jet of water
- Apply insecticidal soap to heavy infestations
Dark leaf spots, sometimes with a yellow ring
Those round brown spots that show up in wet, sticky weather are usually just fungal leaf spot. They start out pretty round, and they can run together once more leaves catch it. Pull off the worst leaves, water down at the base instead of over the top, and give the vine some elbow room so the leaves dry off quick.
Fix:
- Remove and discard badly affected leaves
- Improve air circulation and avoid overhead watering
Toxicity
Think of those colorful pods as a look, don't eat kind of plant. The raw mature seeds and pods hold cyanogenic glycosides that are toxic to people and animals alike, and only cooking the young pods all the way through makes them safe. Keep the glossy pods and seeds away from kids, pets, and grazing animals.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
If a cat chews the raw seeds or pods, the cyanogenic compounds can leave it drooling, throwing up, and nursing a sore belly, so it's best to keep those glossy pods somewhere it can't get to them.
Dogs Caution
Dogs are the ones most likely to go for the bright pods, and raw beans can bring on an upset stomach, retching, and a droopy, tired dog, so pick up any pods that drop where a nosy pup hangs out.
Horses Caution
Those same cyanide-releasing compounds in the raw beans and leaves can leave a horse weak, breathing hard, and not interested in food, so it's smart to fence the vine off from where horses graze.
Rabbits Caution
Raw seeds and pods aren't safe for rabbits to nibble and can upset their gut and leave them sluggish, so don't hand over any trimmings off the vine.
Livestock Caution
Cattle, goats, and sheep can get cyanide poisoning from a big feed of raw beans, and in bad cases that means staggering, hard breathing, and collapse, so keep them off any planting that's gone to pod.
Birds Caution
Pet and backyard birds shouldn't be pecking the raw mature seeds either, since they carry the same cyanogenic glycosides, so stick with feed you already know is safe.
People Young cooked pods safe
Here's the good part: plenty of countries eat the young pods once they're cooked all the way through. The raw mature beans are a whole different story, though, and need boiling in several changes of water first, since raw they release cyanide that can cause nausea, dizziness, and worse. So never eat the raw beans or pods.
Keep the colorful pods and seeds away from children and curious pets; never eat raw mature beans or pods. Only thoroughly cooked beans are safe.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
A handful of named forms show up in gardens, and they mostly differ by flower and pod color. Here are the two worth knowing.
Ruby Moon
This is the ornamental one you'll run into most, and it's easy to spot thanks to its deep purple stems and shiny reddish-purple flat pods that keep your attention all season.
Alba (white-flowered form)
This one's a white-flowered, white-seeded version with plain green pods, so it leaves out the purple that the usual type shows off.
How to propagate
Hyacinth bean grows from seed, and it comes up fast and climbs even faster, so a single packet will cover a good stretch of trellis in one warm season.
SeedEasy
Sow outdoors after frost when soil is warm, or start indoors 6 to 8 weeks before the last frost. · Germinates in roughly 1 to 3 weeks; grows rapidly to cover a trellis in a single season
You'll grow hyacinth bean from seed every year, either sowing outdoors after frost once the soil's warm or starting indoors 6 to 8 weeks before the last frost. The seed coat is tough, so soaking or nicking it speeds up the 1 to 3 week germination, and after that the vine just races up a trellis in a single season. Get a sturdy trellis or arbor in place before it takes off, and grab some seed in fall so you can replant next spring.
Myths
It's a bean, so the pods and seeds are fine to eat raw right off the vine.
Easy mistake, but the raw mature seeds and pods carry cyanogenic glycosides and are toxic eaten raw. The mature beans are only safe after real cooking, boiled in several changes of water, and here in the US the plant is mostly grown to look at, not to eat.