A small update and thanks for all the thumbs up.
Robin, If I pot up promptly, a good percentage of my Japanese seedlings flower in their second year and by the third year they all should pretty much bloom.This batch was not potted up beyond 140mm pot in their first year and only this year they went into 200mm pots, (4.5 litres,) instead of the deep 6 litre pots.In other words , they were not looked after properly and I think flowering will be less with these seedlings.Quite a few are running up to bloom, so not long to wait.
Just a shot of how they are at the moment.I've set up now black plastic underneath one batch of the 200mm pots, put timber strategically across to form a pool and raised up the side on the left with some old timber poles.I think these plants in the 200mm pots would dry out during flowering without my attempt at creating some sort of pool, whereas those plants in the deep 6 litre pots are fine, even during our heat waves.(the flower of course will still burn).The soil mix though is richer, a heck of a lot of cow dung and rotted down seaweed.