There's a thread further down on the page with information.

Here is a link that might be useful: B. grandis bulbils

I followed the link and see you can start them indoors but you don't have to do you????? :)

I can't grow the hardy begonias in my climate, but I believe someone on that thread mentioned that the ones started indoors have a head start on the ones that come up in the garden. So, no, you don't have to.

I just leave them in the dirt around
the parent plants - after a couple of years you can have a clump of over 100 plants - I dig and pot some of the bigger bulbs each spring for local plant sales. I have both grandis, and the white flowered form, also a hybrid called B. Torsa that has HUGE leaves to 2 ft across. bob

Bob or anyone,who has b. 'Torsa' bulbils to trade or for postage,please email me. My email is on My Page.
Thanks.

Here's 'My Page',here.
Thanks.