WateringTimesWatering plan, $19
Begonia grandis, WUCOLS IV

How often to water hardy begonia in California

In July in the Central Valley, established hardy begonia in loam needs a deep watering about every 5 days: about 1.5 gallons each time for a plant 2 feet across, about 1.9 gallons a week. Hardy begonia is a tuberous perennial from southern China and Japan that forms a bushy mound about 2 feet tall in shade. Its large, lopsided leaves are olive green above and red-veined beneath. Pink flowers hang in loose clusters from summer into fall. It wants soil that never dries out, then dies back to rest in winter.

PerennialRated for 4 of 6 zones

How often to water hardy begonia, 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 hardy begonia 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 foot 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 an inch or two down under the leaves means hardy begonia needs water, since its soil should not dry out
  • Large leaves that sag on a warm afternoon over dry soil point to a thirsty clump
  • Stems yellowing and collapsing in fall are normal dormancy as the days shorten, not a call for more water
  • Wilting stems over soil that stays soggy for days can point to poor drainage rather than thirst
  • Powdery white patches on fading fall leaves are mildew, which this begonia can pick up once it goes dormant

How to water it

  • Water at the base of the clump with drip or a soaker hose, keeping the big leaves dry
  • Soak the root area about 8 inches deep, and water again before the top inch dries out
  • Mulch the bed with compost or leaf mold to keep the soil cool and moist through summer
  • Plant in organically rich soil that drains well, in part shade to full shade
  • Widen the watered area as bulbils dropped in fall sprout into new plants around the clump

Through the seasons

Keep a new hardy begonia evenly moist through its first summer while the tuber settles in. Established clumps still need soil that does not dry out from late spring through bloom. Flowers open from July into October. As days shorten, the plant goes dormant, drops small bulbils from its leaf joints, and dies back for winter. New shoots are late to appear in spring, so do not dig or flood the spot. Winter rain covers the dormant months on the coast and in the Central Valley. WUCOLS rates hardy begonia moderate water on the north-central coast, in the Central Valley, on the south coast and in South Inland. WUCOLS marks it as not suited to the high desert or the low desert.

In pots

Hardy begonia can be grown in a container in a shaded spot. Use a rich, well-drained mix and a pot with open drainage holes. Check the mix an inch down every day or two in summer heat, since it should not dry out. Water until it drains, then empty the saucer. After the stems die back in fall, the resting tuber needs much less, so water sparingly through winter. Keep the pot where you will remember it in spring, because new shoots appear late.

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

Hardy Begonia: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.78––
Feb0.530.650.810.87––
Mar0.871.091.151.3––
Apr1.181.521.41.61––
May1.462.081.611.95––
Jun1.612.481.742.29––
Jul1.612.671.982.51––
Aug1.492.391.862.33––
Sep1.241.81.491.86––
Oct0.871.181.151.33––
Nov0.470.560.840.9––
Dec0.310.340.650.68––
Year1217.1115.518.41––

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 hardy begonia. Plants that drink alike can share one valve and one schedule.

DahliasDahlia spp.moderate water, Central Valley2.67 gal/sq ft in JulyFernsNephrolepis cordifolia (SHADE IN DESERT)moderate water, Central Valley2.67 gal/sq ft in JulyDayliliesHemerocallis spp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBegoniasBegonia & ssp. & cvs. (shade in the desert)moderate water, Central Valley2.67 gal/sq ft in JulyCalla LiliesZantedeschia aethiopica SHADE IN DESERTmoderate water, Central Valley2.67 gal/sq ft in JulySageSalvia officinalis and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBicolor MonkshoodAconitum cammarummoderate water, Central Valley2.67 gal/sq ft in JulyGarden MonkshoodAconitum napellusmoderate water, Central Valley2.67 gal/sq ft in JulyCarpet BugleAjuga reptans (shade)moderate water, Central Valley2.67 gal/sq ft in JulySnowdrop WindflowerAnemone sylvestrismoderate water, Central Valley2.67 gal/sq ft in JulyMountain SandwortArenaria montanamoderate water, Central Valley2.67 gal/sq ft in JulySwamp MilkweedAsclepias incarnatamoderate water, Central Valley2.67 gal/sq ft in JulyOrange MilkweedAsclepias tuberosamoderate water, Central Valley2.67 gal/sq ft in JulyGreater MasterwortAstrantia majormoderate water, Central Valley2.67 gal/sq ft in JulyWax BegoniaBegonia semperflorensmoderate water, Central Valley2.67 gal/sq ft in JulyEnglish DaisyBellis perennismoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

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

AgapanthusAgapanthus orientalislow water, Central Valley1.07 gal/sq ft in JulyGeraniumsPelargonium x hortorum and cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyIrisesIris germanicalow water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyYarrowAchillea millefolium (non-native hybrids)low water, Central Valley1.07 gal/sq ft in JulyMountain AlyssumAlyssum montanumlow water, Central Valley1.07 gal/sq ft in JulySilver SageSalvia argentealow water, Central Valley1.07 gal/sq ft in JulyPurple MulleinVerbascum phoeniceumlow water, Central Valley1.07 gal/sq ft in JulySilvery YarrowAchillea clavennaelow water, Central Valley1.07 gal/sq ft in JulyFern Leaf YarrowAchillea filipendulinalow water, Central Valley1.07 gal/sq ft in JulyCalifornia Native YarrowAchillea millefolium (CA native cultivars)low water, Central Valley1.07 gal/sq ft in JulyWoolly YarrowAchillea tomentosalow water, Central Valley1.07 gal/sq ft in JulyPerennial HollyhockAlcea rosea cvs.low water, Central Valley1.07 gal/sq ft in JulyMountain Lady's MantleAlchemilla alpinalow 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 hardy begonia, 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 hardy begonia in summer?

In July, established hardy begonia in loam needs a deep watering about every 5 days in the Central Valley, about every 7 days on the south coast and about every 6 days in the South Inland zone. 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 hardy begonia need per day?

In July in the Central Valley, established hardy begonia 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 hardy begonia change across California?

Yes. WUCOLS rates hardy begonia 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, moderate water in the South Inland zone, not suited to this region in the High and Intermediate Desert zone, not suited to this region in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Is hardy begonia poisonous to pets?

Yes. It is listed as a problem for cats, dogs and horses, and the underground roots are the most toxic part. The sap can also irritate skin, so wear gloves when you divide it.

Why did my hardy begonia disappear in winter?

It is a herbaceous perennial that goes dormant as days shorten and dies back to the ground. New growth is late to appear in spring. Mark the spot so the clump is not dug up before it returns.

How does hardy begonia spread?

Small bulbils, about the size of a small pea, form in the leaf joints in fall and drop to the ground. They sprout the next spring, so one or two plants become a small colony after a couple of years. It can also self-seed.

Can hardy begonia take sun?

It is a plant for part shade to deep shade. Pick a spot under trees or on the shaded side of a building. In a brighter spot, expect to check the soil more often.

How cold can hardy begonia take?

It tolerates temperatures down to about 23 degrees F. Where winters run colder, a heavy mulch over the dormant clump helps it through. The tuber rests below ground until spring.

Should I deadhead hardy begonia?

Yes, if you want a longer show. Removing spent flowers extends the bloom period. Leave some late flowers if you want seedlings, since plants can also self-seed.

More plant watering guides

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Sources