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OrnamentalbulbousSome care needed

Tuberous begonia

Begonia × tuberhybrida

The summer container plant that flowers hardest in shade, which almost nothing else does: heavy double blooms or trailing curtains of them, from June until the frosts, on a north-facing doorstep where geraniums sulk. The tuber is lifted and kept dry over winter and lasts for years.

Position
Partial shade or Dappled shade or Full shade
Water
moderate demand
Drainage
Free-draining, Moisture-retentive
Grows to
25–45 cm × 30–50 cm
Hardiness
H2
Harvest
October
Difficulty
Some care needed

August

In flower

Tuberous begonia’s year

Resolved for United Kingdom (general). Every window is stored against a climate event rather than a date, so a late frost pocket runs later than the band shows. What else August calls for.

ActivityJFMAMJJASOND
PlantMay. June.
In flowerJune. July. August. September.
HarvestOctober.

Timing that travels

The band above resolves this plant's windows into months for one region. These are the windows themselves, stored against a climate event rather than a date — which is the form that survives being carried to a colder garden, a frost pocket, or next year.

Conditions it needs

Light
Partial shade, Dappled shade, Full shade
Frost
Frost tender
Hardiness rating
H2 (RHS)
Grows best at
15–26 °C
Soil
Peat-free compost, Loam
Soil pH
5.5–6.5
Drainage
Free-draining, Moisture-retentive
Water needs
moderate
Drought
poor tolerance
Waterlogging
poor tolerance
Heat
moderate tolerance
Wind and exposure
poor tolerance
Where these figures come from
LightSourced guidancemoderate confidence
  • Royal Horticultural Society: Tuberous begonia — position

Checked 2026-08-13

FrostSourced guidancehigh confidence
  • Royal Horticultural Society: Tuberous begonia — hardiness

Checked 2026-08-13

Hardiness ratingSourced guidancemoderate confidence
  • Royal Horticultural Society: RHS hardiness ratings

Checked 2026-08-13

Grows best atSourced guidancemoderate confidence
  • Royal Horticultural Society: Tuberous begonia — temperature

Checked 2026-08-13

SoilSourced guidancemoderate confidence
  • Royal Horticultural Society: Tuberous begonia — soil

Checked 2026-08-13

Soil pHSourced guidancemoderate confidence
  • Plant Finder — Missouri Botanical Garden: Begonia × tuberhybrida — culture

Checked 2026-08-13

DrainageSourced guidancemoderate confidence
  • Royal Horticultural Society: Tuberous begonia — soil

Checked 2026-08-13

Water needsHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

DroughtHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

WaterloggingHorticultural consensusmoderate confidence

The tuber rots readily in wet compost.

No external citation — see the evidence type above.

Checked 2026-08-13

HeatHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Wind and exposureHorticultural consensusmoderate confidence

Brittle stems snap in wind.

No external citation — see the evidence type above.

Checked 2026-08-13

On your soil

Computed by comparing this plant's recorded requirements against each soil's recorded characteristics. A recorded horticultural fact overrides the comparison where GrowingHQ holds one.

SoilVerdictWhy
Heavy clayWorks, with one conditionTuberous begonia will crop on heavy clay, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
SandyWorks, with one conditionTuberous begonia will crop on sandy, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Chalky and alkalineStruggles hereTuberous begonia struggles on chalky and alkaline: The soil is substantially too alkaline for it: it wants pH 5.5 to 6.5, and this soil sits around 7.8 to 8.5. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering. A container or a raised bed of imported soil sidesteps the problem entirely.
LoamPrefers this soilLoam suits Tuberous begonia as it stands: The free drainage is exactly what it wants. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
SiltyGrows well hereTuberous begonia grows perfectly well on silty without special measures, though it is not the soil it would choose.
Peaty and acidWorks, with one conditionTuberous begonia will crop on peaty and acid, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Shallow over rockWorks, with one conditionTuberous begonia will crop on shallow over rock, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Made ground and urban soilStruggles hereTuberous begonia struggles on made ground and urban soil: The soil is substantially too alkaline for it: it wants pH 5.5 to 6.5, and this soil sits around 7.2 to 7.8. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold. A container or a raised bed of imported soil sidesteps the problem entirely.

Not sure which you have? Four hand tests will settle it.

Space and spacing

Mature height
25–45 cm
Mature spread
30–50 cm
Rooting depth
20 cm
Spacing
25–35 cm apart
Where these figures come from
Mature heightHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Mature spreadHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Rooting depthHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

SpacingSourced guidancemoderate confidence
  • Royal Horticultural Society: Tuberous begonia — spacing

Checked 2026-08-13

How far apart to plant tuberous begoniaThree tuberous begonia plants drawn in a row at their recorded spacing of 25–35 cm between plants. The spacing is drawn to scale against a one metre rule; the plants themselves are symbols rather than scale drawings, so the distance between them is the part to read.25–35 cm
Measured centre to centre. Plants set closer than this compete for light and water long before they look crowded, and the crowding cannot be undone once they are in.

In a container

Minimum volume
5 litres or more
Minimum depth
20 cm
Where the container figures come from
Minimum volumeHorticultural consensusmoderate confidence
  • Royal Horticultural Society: Begonias — cultivation

Checked 2026-08-13

Minimum depthHorticultural consensusmoderate confidence
  • Royal Horticultural Society: Begonias — cultivation

Checked 2026-08-13

A container plant almost by definition, and one that wants less root room than its size suggests — a tuber in too large a pot sits in cold wet compost and rots. Start it hollow side up and barely covered, in gentle warmth in March. The pendulous types are for baskets and need a sheltered spot; heavy double flowers and wind are a bad combination.

Habit and ultimate size

What the plant becomes, rather than what it is when you buy it. The gap between the two is where most planting mistakes live.

In a container
Good in a container long-term
Where these figures come from
In a containerHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Bulb, corm, rhizome and tuber comparedFour underground storage organs drawn in section at the same scale. A true bulb is layered scales around a growing point on a flat basal plate, and multiplies by offsets that pull apart by hand. A corm is a solid swollen stem base with a bud on top, the previous year's spent corm beneath it and small cormlets at its sides. A rhizome is a horizontal swollen stem that sits at soil level with roots below and a growing point at one end, and must not be buried. A tuber is a swollen stem with growth buds scattered over its whole surface and no basal plate, so a cut piece without a bud on it cannot grow.True bulbbasal plateDaffodil, tulip, lilyPull offsets apart by hand.Cormspent corm below, cormlets asideCrocus, gladiolus, crocosmiaReplaced yearly by a new one on top.Rhizomesoil level — top stays exposedBearded irisCut with a knife. Must not be buried.Tuberbuds scattered, no basal plateCyclamen, potatoA cut piece without a bud will rot.
All four are sold as 'bulbs'. The differences are internal, which is why they are drawn rather than photographed — and each one changes what you physically do with the thing in your hand.
Storage organ
Tuber
Survives winter in the ground
No — lift and store, or treat as annual
Planting depth
2–3 cm
Naturalises
Stays where it is put
Where these figures come from
Storage organSourced guidancehigh confidence
  • Royal Horticultural Society: Begonia × tuberhybrida — propagation

Checked 2026-08-13

Survives winter in the groundSourced guidancehigh confidence
  • Royal Horticultural Society: Begonia × tuberhybrida — hardiness

Checked 2026-08-13

Planting depthSourced guidancemoderate confidence
  • Royal Horticultural Society: Begonia × tuberhybrida — planting depth

Checked 2026-08-13

NaturalisesHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

A swollen underground stem with growth buds scattered over its surface rather than a single basal plate. A piece cut without a bud on it will rot rather than grow.

How deep to plant a bulb, drawn to scaleEight geophytes drawn at one scale against a soil surface line, each at the depth the catalogue records for it. A bearded iris rhizome sits on top of the soil with only its roots buried. A cyclamen tuber and a nerine bulb are barely covered, at 2 to 3 centimetres, the nerine with its neck standing proud. Snowdrops and crocuses go at 8 to 10 centimetres, a daffodil at 10 to 15, a tulip at 15 to 20 and a lily deepest at 15 to 25 centimetres. Most sit at roughly two to three times their own height, and the shallow exceptions are shallow because the organ must bake in the sun to flower.soil surface5 cm10 cm15 cm20 cmBearded irison topon the surfaceCyclamen2 cmjust coveredNerine2 cmneck proudSnowdrop9 cmCrocus9 cmDaffodil13 cmTulip18 cmplant deepLily20 cmstem roots
Two to three times the bulb's own height is the working rule, and the four plants that break it are the four most often planted wrong. A bearded iris buried by mulch or a tidy neighbour will make leaves for years and never flower again.
Lifting and storing. Bring the pot under cover before the first frost, let the top growth yellow and die back naturally, then clean the tuber and store it dry and frost-free. Cutting the stems off while they are still green loses the plant the last of the food it was moving back into the tuber.
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

After flowering. Start it hollow side up, barely covered, in gentle warmth in March. Planted upside down it either rots or spends weeks pushing shoots around the rim, and it is the commonest way one is wasted.
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Where and how you can grow it

Each way of growing is assessed separately, and “not assessed” is a real answer rather than a gap we have filled in with a guess.

MethodSuitabilityWhat it needs
Open groundWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Traditional dug bedWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Raised bedWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

ContainerWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Growing it

  • PlantingStart the tubers hollow side UP, barely covered, in gentle warmth in March. Planted upside down they either rot or waste weeks pushing shoots round the edge, and it is the single commonest mistake with them.
  • HarvestingBring the pot in before the first frost, let the top growth yellow and die back, then clean the tuber off and store it dry in a frost-free place. Unlike a canna, this one wants to be kept properly dry.
  • ProtectionStop watering in early autumn and let the plant die down before lifting, then store the tubers dry and frost-free at about 7 °C and start them again in March. The common mistake is lifting too early: a tuber taken while the plant is still green and flowering has not finished laying down reserves, and it is the one that fails to shoot in spring.
  • WateringKeep the compost evenly moist through the growing season and water the compost rather than the plant — begonia stems and leaves are brittle and succulent, and water sitting in the crown or on the flowers causes rot and grey mould in exactly the humid still conditions these are often grown in. Never let a plant in full flower dry out to the point of wilting: bud drop follows a few days later, when the cause looks unrelated. Reduce watering from September and stop as the foliage yellows, so the tuber goes into store dry and clean.
  • FeedingFeed fortnightly with a high-potash feed once the plant is growing strongly and in bud. Tomato food suits it. Too much nitrogen gives large soft leaves, few flowers and stems that snap under the weight of the doubles, which is the commonest disappointment with the big pendulous types in baskets. Stop feeding at the end of August so growth hardens off before the tuber has to go into store.
Where this guidance comes from
PlantingSourced guidancehigh confidence
  • Royal Horticultural Society: Begonia — starting tubers

Checked 2026-08-13

HarvestingSourced guidancemoderate confidence
  • Plant Finder — Missouri Botanical Garden: Begonia × tuberhybrida — culture

Checked 2026-08-13

ProtectionSourced guidancehigh confidence
  • Royal Horticultural Society: Begonia — overwintering

Checked 2026-08-13

WateringSourced guidancehigh confidence
  • Royal Horticultural Society: Begonias — cultivation

Checked 2026-08-13

FeedingSourced guidancemoderate confidence
  • Royal Horticultural Society: Begonias — cultivation

Checked 2026-08-13

Harvesting

  • When it is readyLift the tubers when the leaves yellow and the plant stops flowering, or straight after the first frost — usually October. Stop watering a few weeks beforehand and let the plant die down naturally, because a tuber lifted while still in full growth has not built up the reserves it needs to come through the winter.
  • How to pick itLift the tuber with the stems still attached, shake the soil off and lay it in a tray somewhere dry and frost-free. The stems shrivel and fall away of their own accord after a week or two, which is the moment to clean the tuber up — pulling them off while still green tears the crown and lets rot in.
  • Keeping itStore dry in trays of dry compost or sand at around 7 °C, hollow side up. Start them back into growth in fresh compost in March.
Where the harvest guidance comes from
When it is readySourced guidancehigh confidence
  • Royal Horticultural Society: Begonia — overwintering

Checked 2026-08-13

How to pick itSourced guidancehigh confidence
  • Royal Horticultural Society: Begonia — lifting and storing

Checked 2026-08-13

Keeping itHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Safety and edibility

Cats and dogsPainful or persistently unwell; veterinary advice worth takingListed at genus level

Listed as harmful to cats or dogs

Tuberous begonia is listed as harmful if eaten. Soluble calcium oxalates throughout, concentrated in the underground tuber. Chewing the leaves causes intense burning of the mouth and difficulty swallowing; the tuber is the part that carries a real risk of kidney injury in a dog that digs one up and eats it, which is the realistic scenario for a plant lifted and stored over winter.
source

Sourced guidancehigh confidence

  • ASPCA Animal Poison Control Center — toxic and non-toxic plant list — American Society for the Prevention of Cruelty to Animals: Begonia — toxic plants list

Checked 2026-08-13

Affected parts: tuber, leaf.

  • ToxicitypetsSoluble calcium oxalates throughout, concentrated in the tuber. Chewed leaves cause burning of the mouth and difficulty swallowing; the tuber is the part that carries a real risk of kidney injury to a dog that eats one. The risk peaks out of season rather than in it — the tubers are lifted in autumn and stored somewhere like a shed or a garage, which is exactly where a dog finds them.
    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Begonia — toxicity

    Checked 2026-08-13

    Store lifted tubers in a closed box on a shelf rather than in an open tray at floor level.

Sources for this page

GrowingHQ editorial synthesis · Plant Finder · Royal Horticultural Society

Each figure on this page carries its own citation, under the “where these figures come from” note in its section. Record last reviewed 2026-08-14.