Hi Jonathan, I am going to follow this, as this is not in questions on the Begonia Page.
So thanks for the question and I hope you get an answer soon.

Best to snip them with something sharp if we do, rather than pinching with fingers.

My eyes are failing me again. I will look forward to rejoining you tomorrow.

Sorry to hear that Jonathan, hopefully you will have answer tomorrow? Take care Denise x

Try sending David a pm he will know the answer.

Eyes still blind today, but will be Ok by tomorrow I hope.

Sorry to hear this Jon, it must be hard for you.

Hi again. Am fine today thanks. Still no solving of mystery re pinching though. Surely somebody must know. My own begonias do always seem to bloom like mad even though I have never pinched them before. My summer display is always predominantly begonias, as I find they out-perform just about any other bedding.

I have never grown them so I will not even guess .
Begoniafan, Marksbegonias, Bloomer, and Yorkshire all grow them. I will ask them to have a look at your question and anwser you.