I would like to buy some begonia grandis seeds to winter sow. Please list online sources. Thanks
If you can't find any online stores, you might try contacting eBay sellers who auction seeds to see if they have begonia grandis seeds but just haven't listed them.
For some reason I don't recall seeing B. grandis listed as seed. The plants produce enormous quantities of seed, which doesn't require a cold period to germinate (i.e., does not require winter sowing). I have propagated it very easily by sowing seeds indoors but have yet to see a single seedling appear spontaneously in my garden (although it spreads all too readily by bulbils).
I have tons of seeds of the pink form and would be happy to send you some if you will send me a self-addressed stamped envelope. Email me at email@example.com (remove "xyz") if you're interested. I may also have seeds of the white form but they would be 2 or 3 years old. (All are open-pollinated so I can't guarantee the color of the seedlings!)
Gardens North has seeds and bublils.
Here is a link that might be useful: Gardens North