Indoor Bonsai

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DORMANCY

As previously stated, woody temperate-climate plants require a dormant period. This is a period of at least 42 days where temperatures are 10°C or lower. Most deciduous trees will lose their leaves at this time whilst some others such as Ulmus parvifolia, the Chinese Elm may remain evergreen. Evergreen species, in particular conifers will slow their growth rate considerably.

However, tropical species do not have a dormant period as such and will continue to grow all year round.


AIR CIRCULATION AND HUMIDITY

Central heating systems radically reduce humidity in our homes to near desert levels. All bonsai need good humidity levels to grow well indoors and there are several ways to address this problem.

Firstly, never place your bonsai above a radiator where humidity levels are especially poor. In general, radiators should be avoided as they also cause wild fluctuations in temperature to their the surrounding environment.

Secondly, trees can be misted to create higher humidity levels. Misting also cleans the leaves of dust and dirt that would otherwise collect. Don't bother however misting religiously everyday, as excessive misting can build up salt deposits on leaves and water runoff can result in over-wet bonsai compost. It is far more important that the surrounding area is kept humid and this is best provided by use of a humidity or gravel tray. This is a flat tray that holds water into which small stones or pebbles are placed. The bonsai is placed on top of the stones so none of the pot touches the water, as the water evaporates over the course of 1 or 2 days it provides a continual humid atmosphere around the tree. It is important that the bonsai pot can still drain fully and it should sit high enough above the water in the humidity tray to be able to do so.


PESTS AND DISEASES

Trees are just as likely to be attacked by pets and diseases inside as they are out. Bugs that would normally be killed outside during the cold of winter are able to thrive indoors year round!

Special attention should be paid to spider mites which positively enjoy the low humidity indoor environment. Spider mites cannot be seen with the naked eye but their presence can be noted by the appearance of very fine webbing between leaves. These can be dealt with using ordinary insecticides.

Fungus gnats are very small fly-like bugs that can occasionally be found in and around the compost of bonsai, these are nearly always drawn to over-wet composts and can be dealt with using insecticides. If the compost of the bonsai is found to be too wet all the time, consider a change in your watering practices or compost if it is poor draining. Fungus gnats are nearly always brought indoors when moss growing on the surface of the compost is not removed beforehand.



SUMMARY

Growing bonsai indoors successfully is not straightforward; many trees can continue to grow seemingly unaffected for anything up to 1 or 2 years before showing any outward signs of distress. However, after this time, trees tend to have lost so much health and vigour that they are very hard to keep alive. Do not assume that the tree you brought growing indoors at the garden centre or bonsai retailer will grow indoors on a permanent basis. Very often, outdoor species are sold in an indoor environment simply for the convenience of the retailer. Always ask retailers if your tree is intended for indoor or outdoor cultivation. It should be noted here that you cannot SUCCESSFULLY cultivate coniferous bonsai indoors for more than 1-2 years. It has literally never be done before.

If you specifically require a tree for growing indoors, choose a species that will be more able to cope with this stressful environment. This typically means using tropical species that have little dormancy needs and can tolerate low light levels and poor humidity.
Place your tree on a well lit window-sill that is not shut off at night and is not above a radiator. Ensure that the leaves are not burnt in strong sunlight. Make use of a humidity tray and enjoy!!