Begonias: outdoors

Used in containers, hanging baskets and bedding schemes, begonias provide continuous colour throughout the summer until the first frosts. They are easy to care for and all grow well in partial shade.

Begonia On Top Pink Halo

Quick facts

Common name Begonia
Botanical name Begonia
Group Tender perennial
Flowering time Summer
Planting time Start into growth in early spring, plant outside after frosts
Height and spread Both 15-50cm (6-20in)
Aspect Sun or partial shade
Hardiness Tender
Difficulty Easy, moderate or difficult

Cultivation notes

Tuberous begonias are ideally suited to growing in containers and hanging baskets, whilst fibrous rooted begonias make an attractive addition to summer bedding schemes.

Begonias for the garden have different cultivation needs so the notes below will help guide you to success.

Tuberous begonia

Cultivars which are usually derived from Begonia × tuberhybrida are a favourite of gardeners for their bright colours and long flowering season. Male and female flowers are borne separately on the same plant, the male flowers being the showiest. Selections and hybrids of B. boliviensis such as Begonia ‘Million Kisses’ are also available and are excellent free flowering plants for baskets and pots.

  • Start tubers into growth in March or April at 18°C (64°F)
  • Fill a seed tray 7.5cm (3in) deep with moist sandy potting compost
  • Place tubers on the surface of the compost hollow side uppermost 2cm (¾in) apart, 2.5cm (1in) deep
  • When the leaves are showing pot into individual 10-12.5cm (4-5in) pots of John Innes No 2 compost or multipurpose compost, including peat-free ones
  • Plants can be hardened off and planted outside after the danger of frost has passed
  • Feed every week with high potassium feed (e.g. tomato fertiliser) from four-six weeks after their final re-potting until September
  • Position in sun or partial shade. In borders ensure the soil is fertile
  • Water regularly during dry periods but avoid wetting the foliage

Overwintering

  • Tuberous begonias need to be lifted before the first frosts. The leaves will begin to yellow naturally at which time watering should be reduced. The dry tubers should be stored in barely moist soil or sand in a frost-free shed, ideally at 7°C (45°F) and watered occasionally to prevent shrivelling 
  • The tubers of Begonia ‘Million Kisses’ may be small at the end of the first season but may then over-winter, however most gardeners replace their plants each year

Hardy begonia

Hardy tuberous begonia can be an exotic addition to shady borders particularly in late summer. The most hardy to try is Begonia grandis subsp. evansiana AGM is hardy down to 0°C (32°F).

  • Plant tubers 5-7.5cm (2-3in) deep in reasonably fertile well-drained soil and in a sunny, sheltered position
  • In mild areas tubers can be left in the ground all year if planted at the base of a warm south-facing wall and mulched to provide winter protection
  • Alternatively, start the tubers indoors at 10 °C, pot one tuber to a 10cm (4in) container
  • Plant out once danger of frost has passed
  • As the leaves turn yellow in autumn dry the tubers and overwinter at a minimum of 2-4°C (35-40°F)

Semperflorens begonia

These fibrous-rooted, tender perennial begonias are usually grown as annuals. Their flowers can be white, pink or red and are produced throughout the summer until the first frosts. The compact plants can also have attractive foliage. They are one of the few bedding plants that are satisfactory in partial shade. Grow from seed or buy young plants.

  • Plants can be hardened off and planted outside after the danger of frost has passed
  • Feed containers every week with high potassium feed during the summer
  • Position in sun or partial shade
  • Water regularly during dry periods but avoid wetting the foliage

Pruning and training

If growing tuberous begonias for show the female flowers can be removed but there is no need to do this for garden displays. The stem and foliage can be brittle so support with canes as the plant grows.

Propagation

Tuberous and semperflorens begonias have different growing habits and therefore require different propagation methods.

Tuberous begonias

Division (Sectioning)

  • Start the tubers into growth as usual
  • When the shoots appear cut the tuber into sections, making sure each one has at least one bud
  • Leave to callous for a few hours and then pot into individual pots placing the tuber level with the surface of the compost
  • Only existing roots will develop; rootless sections of tuber will not grow

Stem cuttings

  • Take 4in (10cm) with a heel (section of tuber) in April, insert into a sandy rooting compost with some bottom heat of 18-21°C (64-70°F)

Semperflorens begonia

  • Seeds should be sown in pots or trays of seed or multi-purpose compost in February or March and maintained at 21–25°C (73–80°F)
  • The seeds are very small, delicate and vulnerable to rough handling. They should be sown on the surface of the compost as light is needed for germination. Cover with clingfilm or if prefered no more than a light dusting of silver sand
  • When the seedlings have produced their first true leaf, prick off into boxes of fresh compost and grow on, potting first into 7.5cm (3in) pots, then into 13cm (5in) pots
  • Double-flowered cultivars of B. semperflorens Cultorum Group are generally propagated from stem cuttings. Overwinter the plants in a cool greenhouse, conservatory or sunny windowsill. Take 7.5–10cm (3–4in) cuttings in April, insert in sandy rooting compost and root with bottom heat of 18–21°C (64–70°F)

Cultivar Selection

Begonia ‘Million Kisses’ series: features plants with a semi-trailing habit and which are ideal for hanging baskets and containers.
Begonia (Million Kisses Series) ‘Yadev’= Devotion AGM: features slender, sharply pointed green leaves, neatly edged in pale pink, and bright velvety red, pendulous flowers held on pink stems. Plants reach about 40-45cm (16-18in) high through into October, and don’t need deadheading.
Begonia (Illumination Series): a series of cascading begonias, excellent for hanging baskets and available in a range of colours.
Begonia (Illumination Series) ‘Illumination Orange’ AGM: Vivid red-orange semi-double flowers on red stems, held over hairy green foliage with yellow-orange margins.
Begonia 'Ambassador Rose' (ambassador series): is a free-flowering semperflorens begonia to 20cm, with glossy, red-edged green foliage and single pink flowers with yellow stamens, produced all summer.

Problems

Watch out for common problems;

  • Tubers may rot in over-wet conditions; make sure compost is well drained and stand pots on pot feet to help prevent waterlogging
  • Flower drop may be a sign of over-dry compost
  • Tubers can rot in storage so check regularly
  • Tuberous begonias may suffer from powdery mildew, fungal leaf spots, or occasionally phytophthora root rot
  • Damping off may be a problem in young seedlings
  • Foliage may scorch in hot sun

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