Credit : The following articles were writen by Harry Harrington. This information is extremely helpful for beginners starting out in the world of bonsai.
Bonsai Basics
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Placement
Nearly all beginners start out by buying a bonsai from a garden centre, shopping mall or (hopefully) a reputable dealer and are often given summary advice. Unfortunately, unless you buy your tree from a reputable bonsai dealer, you may well have started on the back foot. The most common misunderstanding that beginners have (and bonsai forum posts can confirm this) is that Bonsai are still trees and need outdoor living conditions. Trees need good light, good humidity levels, good air circulation and importantly, many species NEED the cold of winter to go dormant. Inside our homes, trees receive comparatively poor light levels and the dry air /low humidity levels created by central heating systems can cause many problems.
There are species that will tolerate indoor conditions and with the correct placement and care can thrive; there are also many species that are not hardy enough to tolerate the winter cold. But, these are in the minority. It is far more difficult to cultivate indoor Bonsai than outdoor Bonsai. Outdoor species very rarely die immediately when grown inside, they can survive for months. However they slowly lose their health and vigour in the adverse conditions they have to cope with, and become susceptible to bugs and disease until they finally start to show outward signs of ill-health; yellowing leaves, lose of foliage and eventually death.
Unfortunately, unscrupulous dealers take advantage of this delayed response to poor care and will display and sell outdoor trees as indoor bonsai. A tree purchased from such a retailer may have been grown inside for weeks or months and can be near death without any outward sign. The most common bonsai to cause problems for beginners are Conifers and very often Junipers. There is NO coniferous species that can tolerate indoor cultivation for more than 2 or 3 years.
Watering
This seemingly easy technique is the second most common cause of Bonsai-related problems. Under-watering or allowing the compost to dry out completely will instantly kill or badly damage most trees; however over-watering can just as equally cause ill-health and eventual death from root-rot and disease.
The most important rule to remember is that trees should be CHECKED for their water requirement daily but should only be watered as required. Never, never water to a routine, this can lead to continually sodden compost which literally suffocates the roots. The surface of the compost MUST be starting to dry out between waterings, then the tree can be thoroughly watered again. The time between waterings can vary from 12 hours to 7 days depending on factors such as prevailing temperatures, wind and humidity levels.
Fiddling
Don't fiddle! The temptation for beginners is to continually fiddle with their tree(s), cutting bits off here and there, continually watering, misting, moving them around etc etc. Checking daily for water requirements and health problems is necessary, but otherwise leave the tree to grow and simply enjoy looking at it! Pruning back to shape is necessary but don't continually jump onto every out of place leaf. In order to keep the tree healthy and vigorous it needs to be able to grow freely at times. It is also important to remember timing is very important, don't carry out jobs such as re-potting or major restyling at the wrong time of the year as this can lead to poor health in the tree and lack of vigour. A tree repotted at the wrong time of year for instance may survive if you are lucky, it may even grow a bit, but, it will very rarely reward you with vigour.
Pruning and re-potting.
Bonsai need to be pruned, this keeps them small, an unpruned bonsai simply becomes an ordinary tree. This is an area that you need to investigate once the basics of watering and placement are understood. If at first you are unsure, simply prune back your trees' new growth to its original shape when it has extended but don't prune every new leaf that appears as it appears. By studying your tree, watching its growth patterns and studying other peoples trees on the internet and in books, you will be able to form a mental picture of how you wish your tree to develop over the coming years. It may be that you wish it to remain as it is, or, that there are areas that could be improved. You need to establish your goals for the tree in order to be able to prune and style it for the future rather than just randomly cutting areas of growth back.
The other area of bonsai that needs to be addressed by the beginner is repotting; a very straightforward technique if carried out correctly and at the right time. Most trees need to be repotted annually or at very least bi-annually in Spring as the years new growth starts to appear. Trees that are not repotted will eventually lose their health and vigour.
Age
How old is my tree? The ONLY way of accurately aging a tree is by counting the tree-rings at the base of the trunk, obviously this is not possible! Normally the age of a tree can be reasonably estimated when a tree has been owned by the same person who propagated it from seed or a cutting; nursery stock can often be estimated reliably at being 2 or 3 years old when bought from a garden centre. Old branches that are removed can also have their rings counted which can also give an indication of the age of the rest of the tree. However, with increased age in bonsai comes increased financial value and this does not always result in complete honesty. There are many bonsai techniques available to the experienced collector that help give the impression of great age; that is after all one of the principal aims when styling and developing trees. Field-grown trees for instance will always display far thicker trunks than trees that have always been grown as bonsai. It is very feasible to create a bonsai from a cutting that after 10 years looks older than a 30 year old container-developed bonsai.
When valuing a tree, it is not its actual age that is most important; it is the impression of age that gives it beauty.
It is hoped that armed with these basics you can keep your bonsai healthy and provide a platform from which to learn a whole new art form. Good luck!