Below is an exert from my new web page, which you may find interesting.
Fig trees will grow into very large specimens, easily 15 m high if you let them. I know of a house in London where you could lean out of a third floor window and pick ripe figs! However, if you want them to fruit well and be of a manageable size, you will need to restrict the roots. This can be done by using a very large pot or tub, such as are used to transport young trees, and sinking it into the ground. Alternatively, books frequently recommend using paving slabs sunk into the ground to form a large box and then filled with not too fertile a soil. Treat them mean and make them keen, if you want lots of fruit, rather than soft sappy growth. Fig trees in pots or tubs benefit from being fed a high potash liquid feed, such as a tomato fertiliser, perhaps once a month during Spring, Summer and Autumn. They will also need to be kept watered if there is a drought.
Figs will be ripe when they start to change colour from bright green to a yellow-green and then develop a brown tinge. You will also notice that they start to droop down and will go slightly soft if gently squeezed with finger and thumb. If left, they will start to expand and split and will attract the unwelcome attention of insects and wasps.
The fruit producing cycle is unusual, in that during the Autumn of year one, they form very small immature fruits. Provided these do not get badly frosted over the Winter, they will reach maturity the following summer, and be ready for harvest during August.
During the Summer, the tree will start to produce another crop of figs, but these will be too small to reach maturity before the Winter starts in the UK. They will fall off along with the leaves in early Winter, as the Fig tree is deciduous. Sadly, this second crop of figs are hard and have not developed any sweetness and are not worth eating.
I have a small fig tree growing OUTSIDE all year in Glasgow. I gave it some additional protection over the Winter.
It is in a sheltered south facing position against a wall and produces one crop of ripe figs each year.
