Collecting seed is not particularly intuitive, and each species is so different in how it likes or doesn’t like to be pollinated. Some species take the first time (like U074, rostrata) others require repeated pollination efforts, using pollen from multiple flowers over the course of a week or more, and even then, they are likely to drop their ovaries prematurely (darth, kapaus).
Begonia cathayana produces quite alot of seed per ovary, but not many flowers in my experience. Seeds were sown in February and germinated quickly, after 1-2 weeks.
Ideally, fewer seeds would be planted per cup. In the moment, the diminuitive size of the seeds (like fine sand) led me to underestimate their ability to ever grow to a large size. A novice mistake! although, the temptation to sow more than is necessary, even when knowing full well the size they will eventually reach, is quite real!
Fortunately all of these plants survived division and repotting. These are the seedlings right before division in mid-May, at about 4 months old.
Seedlings were separated out, as gently as possible, using fine-point tweezers. Randy Kerr advised a knitting needle for its hooked tip, which I’d like to try in the future.
This seedling is especially vigorous and will be held back.
There was an article in the Astro Branch of ABS newsletter, ‘Begonia Chatter’ which said cathayana prefers an acidic growing medium. These seedlings are potted in sphagnum for that reason. In the past, I’d kept adult plants growing in medium with a more neutral pH and can attest, they do not like it.
Two weeks later, after some fertilizer,
Six months later the seedlings are much larger, but still far from adult size,