Greenhouse Gardening – bonsai

If you want to start growing bonsai, visit your local garden centre and select a sapling or small tree to start with - some trees are much happier with the bonsai process than others, so it's important that you take your time and find a tree that is suitable to bonsai but also will feel comfortable in the summer conditions you will be exposing it too. The chosen plant needs to have a slender stem and maybe a few small branches – thick and unyielding trunks and large leaved trees are not ideal as the former is difficult to shape and the latter can drop the leaves through stress and then suffer because it cannot transpire (breathe) through the leaves. Slow growth is important too.

Of course, for most of the year bonsai trees are just like any other which means they will thrive on a life outdoors. This means you should plant your bonsai sapling in the garden until it's reasonably well established before transferring into a ceramic bonsai pot or other shallow container. If you buy your sapling in winter though, it’s probably better put it straight into a ceramic pot and artificially create suitable establishment conditions by moving it into the greenhouse. As most outdoor plants and trees will remain dormant until spring, only greenhouse bonsai can be worked on in the winter months.

Once your sapling is reasonably well established and showing signs of vigorous growth, you have a paradoxical task - because this is the moment to dig it up and inspect the root system, trimming any unwanted or excess growth which is what forces the tree to move into the bonsai process. Long tap roots should be trimmed back by at least half ,and you can take off about one third of the roots every four years. Because bonsai is about balance, you now have to make sure you don’t have too much top growth, although that’s unlikely at this stage, however, if you see any ugly branches or those that are too close together, this is time to remove them. It's always best when bonsai pruning to trim back to a bud which means any new branches will take the direction of that bud.

Greenhouse gardening bonsai photograph by M Shades, used under a creative commons attribution licence