Tender tuberous perennial
How to grow begonias
Begonia × tuberhybrida / B. semperflorens
Begonias are tender, so everything is timed around frost. Start tubers indoors from late February to April at 18 to 21 °C, hollow side up, and plant out in June for flowers until October; bedding begonias go out at the same time. They flower well in part shade, which few summer bedding plants do. Success comes down to careful watering, since wet compost rots the tuber, and a regular high-potassium feed.
- Hardiness
- Tender
- Position
- Part shade to sun (by type)
- Soil
- Free-draining, fertile
- Ideal pH
- 5.5 to 6.5
- Water
- Moderate, let the surface dry between waterings
- Feeding
- Moderate feeder
Sowing and planting begonias
WhenStart tubers Feb to Apr indoors; plant out Jun; flowers Jun to Oct; lift before frost
Starting off
Start tubers Feb to Apr in trays of moist compost at 18 to 21 °C, hollow side up and just covered; shoots show in 3 to 4 weeks. Pot on to 12 cm pots and plant out after the last frost in Jun. Semperflorens seed is dust-fine: sow Jan to Feb uncovered at 21 °C, germination 14 to 21 days.
Spacing and planting
Tuberous types 30 cm apart, bedding semperflorens 15 to 20 cm; set tubers hollow side up, barely covered, 2 to 3 cm deep. Fine in a 25 cm pot or basket, which suits pendulous tuberous types best.
Varieties worth growing
- Nonstop Series
- Compact tuberous begonias with double flowers about 8 cm across in clear colours. The dependable choice for pots and shaded bedding, and the tubers can be kept from year to year.
- Illumination Series ('Apricot Shades')
- Trailing tuberous type that fills a hanging basket on its own, with double flowers from June to the frosts.
- B. boliviensis 'Santa Cruz'
- Arching stems of narrow, fiery red single flowers. Takes more sun, wind and rain than the big doubles.
- 'Dragon Wing Red'
- Large, glossy-leaved, fibrous-rooted plant that needs no deadheading and fills a big pot in sun or shade.
- B. semperflorens Ambassador Series
- Green-leaved bedding begonia about 20 cm high for edging and mass planting; flowers through wet summers when other bedding sulks.
Begonias month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Sow B. semperflorens with heat at 21 °C. Check stored tubers.
- February
Start tubers in trays of moist compost at 18 to 21 °C, hollow side up.
- March
Main month to start tubers; April is not too late. Prick out seedlings.
- April
Pot started tubers into 12 cm pots. Buy plug plants and grow on frost-free.
- May
Pot on if roots fill the pot. Harden off in the last ten days of the month.
- June
Plant out after the last frost. Begin feeding when the first flowers open.
- July
Feed fortnightly. Deadhead and clear fallen petals. Stake large doubles.
- August
Keep feeding. Watch for mildew. Apply vine weevil nematodes to pots at the end of the month.
- September
Stop feeding at the start of the month and water less so the tubers ripen.
- October
Lift tubers before the first frost, dry for two weeks and store frost-free. Compost bedding types.
- November
Check stored tubers and remove any that are soft.
- December
Check tubers monthly. Otherwise nothing to do.
Feeding begonias
A moderate feeder that responds to potassium once it is flowering. Nothing while the tuber is starting, a steady flower feed from the first blooms to the end of August, then stop so the tuber ripens. Use the dry feed or the liquid, not both.
A high-potassium feed keeps the blooms coming; don't waterlog the tubers.
Feeding plan
February to May, starting and potting on
Fresh multipurpose compost
No added fertiliser. New compost carries enough for the first six weeks, and a feed on an unrooted tuber encourages rot.
June, planting in beds
100 g/m², the bottom of the label range, raked into the top few centimetres. Repeat once in mid to late July.
First flowers to the end of August, pots and baskets
3 g per litre of compost scattered on the surface every 2 weeks and watered in: about 20 g for a 25 cm pot holding 7 litres.
First flowers to the end of August, as the liquid alternative
Potassium Rich Fertiliser 11% K
1 g per litre of water (10 g in a 10 litre can) every 2 weeks in place of the dry feed, applied to already moist compost.
September onwards
Nothing
Stop all feeding and reduce watering so the tubers ripen before lifting.
Signs to watch
Buds drop before opening
Sudden dryness or a cold draught
Water evenly and keep above 10 °C
Older leaves yellow between the veins
Magnesium short
Epsom salts
Leaves pale and flowers small in a pot
Potash short
High-potash liquid feed every two weeks from Jun
Pests, diseases and problems
Plant wilts and collapses although the compost is moist; tuber hollowed out, with creamy C-shaped grubs in the compost
Vine weevil grubs, which favour begonia tubers in pots
Water nematodes into pots in late August or early September while the compost is warm. Check every tuber when lifting in October and squash any grubs; start again in fresh compost each spring.
White powdery patches on leaves and stems, leaves yellow and drop
Powdery mildew, encouraged by dry roots and still, humid air
Remove affected leaves at once, space plants so air moves between them and water the compost, not the foliage. Do not let pots dry out and then flood.
Stem turns brown and soft at the base and the plant falls over
Stem and tuber rot from overwatering or water sitting in the hollow of the tuber
Water round the edge of the pot and only when the surface has dried. Use free-draining compost and pots with clear drainage holes; a rotted tuber cannot be saved.
Fuzzy grey mould on flowers, leaves and stems in cool, wet weather
Grey mould (botrytis), which starts on fallen petals lodged in the foliage
Pick off spent flowers and fallen petals every few days, and move pots under cover from prolonged rain if you can.
Stored tubers shrivelled, or soft and mouldy, in spring
Stored too warm and dry, or put away while still damp
Dry tubers for two weeks before storing, keep them at 5 to 10 °C and check monthly. Discard soft ones; a slightly shrivelled tuber usually recovers once started into growth.
Pruning
Pruning and care
Deadhead faded flowers; on tuberous types remove the small single female flowers behind each big double. Stake large doubles with a split cane. In Oct, before frost, lift tubers, dry them indoors for two weeks, cut off dead stems and store in dry compost or paper at 5 to 10 °C frost-free until Feb.
Good to knowLift tuberous types before frost and store dry; bedding types are frost-tender.
Growing begonias in pots
Begonias are at their best in containers. One tuberous plant fills a 25 cm pot; three trailing plants fill a 35 cm basket. Use a peat-free multipurpose compost opened up with a fifth perlite or grit, because the fine roots and the tuber both rot in a dense, wet mix. Plant so the top of the tuber is just covered. Water when the top 2 cm is dry and aim at the compost near the rim, never into the crown; in a hot spell that is daily for baskets and every two or three days for pots. Morning sun with afternoon shade gives the longest display, and large double flowers last better out of wind and heavy rain.
Begonias: common questions
Can you leave begonias in the ground over winter?
No, not in most of the UK: begonia tubers are killed by frost and rot in cold, wet soil. Lift tuberous begonias in October before the first frost, dry them for two weeks, and store them in dry compost or paper somewhere frost-free at 5 to 10 °C until February. Bedding begonias are treated as annuals and composted.
Do begonias like sun or shade?
Most begonias do best in part shade, ideally morning sun and afternoon shade. Large double tuberous types scorch in hot midday sun and drop buds in deep shade. Bedding semperflorens, 'Dragon Wing' and the B. boliviensis types take full sun if they are kept watered.
How often should I water begonias in pots?
Water when the top 2 cm of compost has dried, not on a fixed timetable. In summer that usually means every two or three days for a pot and daily for a hanging basket, less in cool or dull weather. Constantly wet compost rots the tuber and the stem base, while letting the pot dry right out makes the buds drop.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.
- Begonias: outdoorsRHS
- How to grow and care for begoniasBBC Gardeners' World Magazine