I am growing both basket and exhibition begonias this year. My first baskets of begonias are the ‘Apricot Shades’ variety from Thompson & Morgan. I was able to save some of the tubers from last year and I started these off in early February using a cloche in the greenhouse and bottom heat from soil warming cable at 20 degrees. This method has worked well for me and there are two easy fill baskets of quite large plants now (early May) and these are being hardened off in the cold frame.
However I have a lot of baskets so I ordered 100 of the jumbo plugs which I potted on in individual cells as seen in the picture below. These will fill 4 baskets and numerous tubs at the end of May. For the exhibition begonias, I had some tubers saved from last year and started these in early February using the same method as for the basket plants. They have been re-potted once since being started. My favourite is a variety called Ziggy, which is a large blush white flower.
I have also started to grow a collection of Thompson & Morgan giant picotee mixed, in a tray of compost (along with one of the tubers saved from last year to the left) which took about 4 weeks. Once the tubers have started, I pot them up individually and growth is speeded up.The most important things when growing in the greenhouse are never to wet the leaves when watering and where possible to shade the plants. I achieve this by using a plastic cloche on a bed of sand which also assists by giving additional protection from night frosts as the greenhouse itself is not heated.