I grow the Dragon Wing every year for about five years now.
I planted seed on January 14th. Here is the set up I use. They are in a greenhouse that is heated to only about 60-65 but on a heat mat set at 70 and covered with the clear plastic dome. If the seed need a bit of water they get spray from the hand pump sprayer filled with tea solution.
I fill my flats with redi-earth soil. It's a seed starting soil. Water with a soulution of Chamomile tea to wet the tray with the soil. I make the tea at 2 cups water with on tea bag. Then pour that into gal. watering can and fill with more water.
Here are my begonias today
Dragon Wings. Still small but looking good.
Bada
This is a new one! We shall see.