If you like begonias you are lucky because there is no genus of plants so suitable for indoor cultivation that offers such a variety of colour and size in flower and leaf. Moreover, if you concentrate on begonias you can casily choose from among the nine hundred or so species a group of some half dozen tha will give you an array of flowers and decorative foliage throughout the year.
Those who specialize or want to do so will of course g oto monographs on the subject. This entry, as others, is written for the non specialist or as a preliminary guide for the novitiate.
Certain general principles can be applied to the cultivation of all begonias. They are sensitive to ower and under watering. They must, therefore, be planted in porous soil which is kept well drained but moist during their active period. To flower well begonias need plenty of light but the possibility of scorching from the direct rays of the sun must be avoided. Tempera tures should be about 20° (68°F) to induce flowering but should be lower once the plant is in bloom ideally below 15° (59°F) They need a balanced fertilizer during the active period every four weeks, not more.
Once this has been said, it is essential to divide begonias into groups to produce some order out of the variety of habit and appearance.
Group II contains some outstanding summer and winter flowering species. When flowering is over the plant should be dried off and, as soon as the leaves have dropped, the stems should be gradually twisted off the tuber and discarded. The rubers should then be stored in a cool, frost proof place, if space is a problem, they can be taken out of their pots and stored in boxes of dry peat of fibre. No light is necessary.
In February or March fort he summer and May ( or June or later if you have growth lamps ) for the winter flowering species, start the plants up again in a temperature of 15-20° (59-68°F) under the general conditions described above.