planted tubers in May, plenty of growth but as yet no flowers...do they not flower first season? If they do what month do they flower in North West England?
Four o'clocks do flower in the first season, but they can be temperamental about it, responding to temperature. This article should tell you more:
https://www.gardeningknowhow.com/ornamental/flowers/four-oclocks/four-oclocks-wont-bloom.htm
Love this bush, but don't know the name or anything about it. Please help.
This is a Four O' Clock.
https://www.gardeningknowhow.com/ornamental/flowers/four-oclocks/four-oclock-plants.htm
I want to thin out my four o'clock flowers and transplant them. How and when can I do this?
Four o'clocks can be transplanted in fall, and in fact many people in cold regions dig them up every fall to keep in the basement until spring. If yours have done well through the winter before, they should do fine if you dig them up now and transplant them to their new locations. They are pretty hardy. Here is some advice on transplanting:
I can't figure out why my plants are not producing seeds like they used to.
This can happen for a few reasons. It is likely that there is not enough potassium, and phosphorus in the soil. Giving fertilizers high in these two can help them produce again.
Here is a link on their care: https://www.gardeningknowhow.com/ornamental/flowers/four-oclocks/four-oclock-plants.htm
How much nitrogen is needed to grow the seeds?
I would not apply any nitrogen until it has some sort of root system to take it up. Having too much may cause them to abort out before they germinate. You can fertilize, but don't do it often. These are not heavy feeders. Just give a very weak all-purpose feed every few weeks. This article will give you more information about them: https://www.gardeningknowhow.com/ornamental/flowers/four-oclocks/four-oclock-plants.htm
What is the germination period?
I just got some seeds, can I go ahead and plant them now in July? Or do I save the seeds til when?
Plant the four o'clock seeds about one-half inch deep in a sunny bed. They are easy to grow from seeds. They're a summer flower, however, so you'll need to store the seeds in a sealed container in your refrigerator and wait to plant them in April of next year.
https://www.gardeningknowhow.com/ornamental/flowers/four-oclocks/four-oclock-plants.htm