Very organized set-up. How do you water? Are the seed trays misted until germination? When do you start fertilizing and with what? This is a great project and you have provided a lot of the set-up. Let's hear the rest of the details. You will of course have wonderful flowers this year but will these make big enough tubers to store for the winter? Looking forward to seeing your progress.

peggiewho - The seedlings were misted only when the mix started to lighten in color with boiled (cooled) water. I water from beneath by placing the plants in a tray until the mix darkens. The seedlings got a dilute solution of Cal-Mag at 50 ppm nitrogen once while in the cells. When they were potted up, I moistened the mix with the same solution and watered a few times with no fertilizer. Now that they have started to take off, they just got another soaking with the fertilizer solution. I will probably begin to water from above next watering with a constant feed of the above. Last time I did this (2006), I had tubers big enough to store for the winter. Here is a shot of what made it through to the following year, plus some named B&L plants:

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Looks like your well planned project will be richly rewarded. You are using lots of light at a distance. I guess that is because they are shade plants. Do you cycle the light off at all? Do you wait until roots come out of the bottom of the pot to up-size the pot? I am pumping you for information because you are so methodical. Your process obviously comes from years of experience and your success from attention to detail. Missed details can doom a project. Trial and error is very instructive but sometimes wearing. I appreciate the product and watering details. Looking forward to more great photos of your project this summer.

not at all familiar with growing Begonias from seed
nor have I paid so much attention to Begonias
But this is indeed very interesting

I came across one called Angel wings a white flower it is ever so pretty as a mature plant

Growing from seed is an undertaking for the dedicated. You can buy pretty nice begonias for not much. Blackmore & Langdon are the top begonia breeders in England. Their tubers are expensive and growing from seed is an inexpensive way to get them. I am inexperienced at growing from seed but clone. I have almost 200 cuttings under lights right now. If the sun don't shine soon, I will have a problem. There are wonderful and interesting plants but local nurseries carry the same plants they had last year. Seed is a good option to get something new. I have a new garden obsession each year that usually develops over winter. Who knows, next year I may try begonias from seed. Most of my friends are flower ignorant but they all point to the tuberous begonia flower and ask, 'What is that?' Angel wing begonias are very nice to.