WateringTimesWatering plan, $19
Lablab purpureus (Dolichos lablab), WUCOLS IV

How often to water hyacinth bean in California

In July in the Central Valley, established hyacinth bean in loam needs a deep watering about every 8 days: about 2.2 gallons each time for a plant 2 feet across, about 1.9 gallons a week. Hyacinth bean is a fast, twining vine in the pea family, grown for purple-tinged leaves, fragrant rose-purple flowers and glossy ruby-purple pods. It is a tender perennial usually grown as a summer annual from seed. Give it full sun, a sturdy trellis and steady moisture while it races to cover its support.

VineRated for 3 of 6 zones

How often to water hyacinth bean, month by month

Your city
Plant width
2 ft
Your soil

Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.

Every month, on your water days. The personal plan prints this for hyacinth bean and the rest of your yard, on the days your water supplier allows.Get the plan for $19

How this is worked out: established roots fill the top 1.5 feet of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.

Which soil do you have?

Dig down a few inches, take a handful of moist soil and squeeze it.

  • Sandy: gritty, falls apart when you open your hand, will not form a ball.
  • Loam: forms a soft ball that crumbles when you poke it.
  • Clay: forms a firm, sticky ball and squeezes out into a ribbon between thumb and finger.

Still not sure? Pick loam. Most garden beds sit between sand and clay.

How to measure plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • Soil dry 2 inches down at the base of the vine means hyacinth bean needs water
  • Leaves wilting in afternoon heat and still limp by evening point to dry roots
  • Lower leaves yellowing over soil that stays wet point to poor drainage, since it needs well drained ground
  • Few flowers and pods on a vine in shade point to too little sun rather than too little water

How to water it

  • Water at the base of the vine with drip or a soaker hose, keeping the leaves dry
  • Soak a foot or more deep, then let the top couple of inches dry before the next watering
  • Sow or plant only after the last frost, into light, well drained soil in full sun
  • Mulch around the base once seedlings are a few inches tall to keep the soil evenly moist
  • Set drip line along the full length of the trellis so every plant in the row gets an even soak

Through the seasons

Sow seed after the last frost or start it indoors six to eight weeks earlier. Keep the soil evenly moist until the vine takes off. It grows fast through summer, flowering from June until frost, with glossy purple pods from late summer. Frost ends the season wherever it comes, so collect dry pods in fall for next year's seed. In frost-free gardens it can live on as a perennial. WUCOLS rates it moderate water on the south coast, in the Central Valley and on the north-central coast. South Inland, the low desert and the high desert have not been evaluated by WUCOLS.

In pots

Hyacinth bean grows well in a large pot with a trellis or obelisk for support. Its fast summer growth draws hard on the mix, so check it daily in hot weather and water when the top inch is dry. Water until it drains from the holes, then empty the saucer. A pot in full sun gives the most flowers and pods. Where frost comes, the vine dies back in fall, so save seed and start fresh next spring.

1 Your climate zone six WUCOLS zones, each from its own reference city
2.67gal per sq ft in JulyModerate water use in the Central Valley zone
A year
17.11 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.671.32.02.70.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.671.32.02.70.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Hyacinth Bean: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.78–––
Feb0.530.650.81–––
Mar0.871.091.15–––
Apr1.181.521.4–––
May1.462.081.61–––
Jun1.612.481.74–––
Jul1.612.671.98–––
Aug1.492.391.86–––
Sep1.241.81.49–––
Oct0.871.181.15–––
Nov0.470.560.84–––
Dec0.310.340.65–––
Year1217.1115.5–––

How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.

Plants with the same water needs 16

Rated moderate water in the Central Valley, like hyacinth bean. Plants that drink alike can share one valve and one schedule.

JasmineJasminum polyanthummoderate water, Central Valley2.67 gal/sq ft in JulyStar JasmineTrachelospermum jasminoides and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyHoneysuckleLonicera japonicamoderate water, Central Valley2.67 gal/sq ft in JulyIvyHedera helixmoderate water, Central Valley2.67 gal/sq ft in JulyGrapevinesVitis vinifera ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyClematisClematis & ssp., hybrids & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyEvergreen ClematisClematis armandiimoderate water, Central Valley2.67 gal/sq ft in JulyWinter CreeperEuonymus fortunei radicansmoderate water, Central Valley2.67 gal/sq ft in JulyArabian JasmineJasminum sambacmoderate water, Central Valley2.67 gal/sq ft in JulyTrumpet HoneysuckleLonicera sempervirensmoderate water, Central Valley2.67 gal/sq ft in JulyPink Trumpet VinePodranea ricasolianamoderate water, Central Valley2.67 gal/sq ft in JulyPotato VineSolanum laxum (jasminoides)moderate water, Central Valley2.67 gal/sq ft in JulyItalian ClematisClematis viticellamoderate water, Central Valley2.67 gal/sq ft in JulyHopsHumulus lupulusmoderate water, Central Valley2.67 gal/sq ft in JulyBoston IvyParthenocissus tricuspidatamoderate water, Central Valley2.67 gal/sq ft in JulyVirginia CreeperParthenocissus quinquefolia ssp. & cvs.moderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 9

Rated lower than hyacinth bean in the Central Valley. Worth a look for a new bed or a lawn replacement.

BougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyWisteriaWisteria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyFlowering WoodbineLonicera periclymenumlow water, Central Valley1.07 gal/sq ft in JulyFleeceflowerFallopia baldschuanica (Polygonum aubertii)low water, Central Valley1.07 gal/sq ft in JulyCarolina JessamineGelsemium sempervirenslow water, Central Valley1.07 gal/sq ft in JulyCecile Brunner RoseRosa 'Cecile Brunner'low water, Central Valley1.07 gal/sq ft in JulyLady Banks RoseRosa banksiaelow water, Central Valley1.07 gal/sq ft in JulyRoger's Red GrapeVitis 'Roger's Red'low water, Central Valley1.07 gal/sq ft in JulyBlue Dawn Morning GloryIpomoea acuminatalow water, Central Valley1.07 gal/sq ft in July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes hyacinth bean, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.

Questions people ask

How often should I water hyacinth bean in summer?

In July, established hyacinth bean in loam needs a deep watering about every 8 days in the Central Valley and about every 11 days on the south coast. Sandy soil holds less water, so waterings come closer together. Clay stretches them. Check the soil before each watering and skip one after a soaking rain.

How much water does hyacinth bean need per day?

In July in the Central Valley, established hyacinth bean needs about 0.3 gallons a day for a plant 2 feet across and about 1.1 gallons a day for a plant 4 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for hyacinth bean change across California?

Yes. WUCOLS rates hyacinth bean separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water in the Central Valley zone, moderate water in the South Coastal zone, not evaluated in the South Inland zone, not evaluated in the High and Intermediate Desert zone, not evaluated in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Can you eat hyacinth beans?

Young pods can be cooked and eaten, and the plant is grown as a vegetable in Africa and Asia. Mature dried seeds are toxic and must be boiled in two changes of water before eating. Never eat the raw seeds.

How fast does hyacinth bean grow?

Fast. It can reach about 20 feet and cover a trellis in a single season. Give it a strong support, since the mature vine is heavy.

Is hyacinth bean a perennial?

Only in frost-free areas, where it can stay in the ground year-round. Elsewhere it is grown as an annual and replanted from seed each spring.

When does hyacinth bean flower?

From early summer until frost, as long as it gets full sun. The purple pods start forming in late summer, often while the vine is still in bloom.

Can hyacinth bean grow as a ground cover?

Yes. Without a support it sprawls across the ground. Water at the base, where the roots are, rather than over the spreading stems.

More plant watering guides

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Sources