Tuberous begonias

Tuberous begonias are grown for their magnificent flowers. They come in many varied tints of white, cream, yellow, orange, pink, red and bi-colours.

Environment: Tuberous begonias do best in partial shade or filtered sunlight and sheltered from strong winds. The right amount of light is often the key to success. The more gentle sunlight tuberous begonias receive, then the larger and more abundant the flowers will be

Starting Tubers: In  Victoria, tubers are started in September and October. It is important that a ‘sprout’ or ‘pink eye’ appears before it is planted (a bit like a dahlia). If your tubers are slow to start, then move them from their cool winter storage to a warm light place. Always plant tubers with concave side uppermost. Young tubers seem to give quicker results.

Place the tubers evenly in an open potting mix allowing 10 cm-15 cm between the tubers for root development. It is essential that the tubers be completely covered as the roots develop from the top and sides of the tuber. A small amount of blood and bone and dolomite can be beneficial.

Watering: Thoroughly water the tubers when first planted so that the medium is universally moist. Do not water again until the surface of the mix begins to dry out. As the plant develops it will require more water but remember that tubers are lost through over-watering.

Temperature: Place pots in a warm spot where they will receive filtered sunlight. A temperature of between 15º C and 22ºC is ideal. This will increase the number of flowers later in the season.

Potting On:  Early November when the tops have reached about 7 cm-10 cm move into 10cm-15cm pots. In December repot into a 5 cm larger pot using the same mix as before. Keep one to two stems (use the rest for cuttings). Attach plant to stake at back of the pot for support if needed. You should remove the buds until the middle of January to encourage larger flowers. With the pendulous varieties it is best to leave on all the flowers for a better display.

Fertilising:  Tuberous begonias do not require much fertiliser until they are in their final pots. Remember, only use fertiliser after the plant has been well watered.

Pests and Diseases: Tuberous begonias are relatively free of these. Powdery mildew is the most serious problem. This can be corrected by adequate air circulation. Spraying with a good systemic fungicide at intervals before flowering can be used. Remove any mildew that appears with cotton wool dipped in methylated spirits.

Resting Period:  In late Autumn withhold water and remove all flowers and growing tips. This will encourage the dying back process or dormancy. Eventually the stem will die back completely and drop off. Store the dry bulbs in a frost-free place during the cold winter months.

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See also our Tuberous begonia image gallery.

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