I have the same begonia that originally came from Jung. I just potted mine up this morning. You will need to start it now in a good peat soil. Make sure it gets enough light until it can go out so it doesn't get leggy. Then harden it off for a few weeks before transplanting it out. Mine were planted in 4 to 6 inch pots depending on the size of the bulb. Haven't had any problems doing it this way with a variety of begonias for 20 years. Good Luck.

Shirley