Begonias are tubers not bulbs. Sowing in green house feb-mar fill box or tray with damp compost put tubers on top 2" apart, put layer of peat on top so they are just covered. temperature 18c 64f. when tubers sprout leaves pot into 5" pots, harden off, end of may ready to plant out after frost.

Planting outdoors: (end of may) Loosen soil,plant tubers just tucking them into soil 8"-12" apart without covering (Indent side facing up) water in.