Many beginners think that bonsai is this little cute indoor plant. They couldn’t be farther from the truth. Bonsai are naturally outdoor trees that are grown in small containers.
And like regular trees, they need to grow outside. Some of the tropical or subtropical species need protection from cold and can be brought inside during winter months, but even they should be taken outside when the weather is warm.
In the magazines and books, you will see photos of bonsai that are taken indoors. Understand, that they’ve been brought inside temporarily for the photo shoot or bonsai show and will be returned outdoors for recovery.
Deciduous and coniferous trees should be grown OUTDOORS for a few reasons. First, climate trees need a period of rest, or you can also say “dormancy”, during the cooler season. That is when trees stop growing and start saving all their energy for Spring.
It is VERY important for the trees to have that rest period. Without it, they will be forced to continue to grow and then will go into a forced dormancy which can be DEADLY.
Another reason is that providing perfect growing conditions indoors is very challenging. It is hard to arrange your house in such a way that trees would get enough light, humidity, and air circulation. And how would you artificially make it cool enough for the trees to go into dormancy without freezing yourself?
Tropical trees are used to warm temperatures all year round. They don’t have dormancy periods and continue to grow all the time. You can keep them indoors most of the year and take them outdoors for a few warm months, but they will NOT be as healthy and vigor as if you would grow them outdoors.
Some of the bonsai that will grow indoors well are Hawaiian Umbrella Tree, Ficus, Baby Jade, Flowering Japanese Mock Orange Tree, Mistletoe Fig, etc.
One of the biggest problems indoors is the lack of bright light. To the human eye, it might look like there is a lot of light in the room, but for many species of woody plants, it is still not sufficient.
The good news is that all species are different and have different light requirements. There are some tropical species that are used to growing in the forest with a lot of shade. They will do much better indoors with the poor lighting.
Since the light levels decrease by 50% every 20 inches away from the window, try to provide your tree with as much light as possible by placing it near the south-facing window. Keep in mind that glass filters out many important UV rays that are needed for the photosynthesis process.
Another way to provide more light is by hanging a fluorescent lamp 6 inches above the plant. Keep these lights on for about 14-16 hours a day. Unfortunately, even after your best efforts, it will be still too dark for ordinary woody temperate species
Lack of light might result in weak growth and over-sized leaves that will be trying to catch more light.
As I was telling you above, tropical species continue to grow all year round while climate trees need a rest period during cooler months that is called “dormancy”. During that time, most of the deciduous trees drop their leaves and slow their growth.
Evergreen trees keep their foliage but also slow their growth rate. The dormancy period lasts at least 6-8 weeks with temperatures below 40F.
Air Circulation and Humidity
Air circulation and humidity are other challenges that you will be facing when growing bonsai trees indoors. While tropical trees need high humidity, climate trees do not, but it is important to make sure the humidity levels indoors do not reach desert levels, especially during winter when the heat is on.
Tropical plants can be misted a few times a day creating higher humidity levels, but in the house with a central heating system that usually is not possible. Another way you can increase humidity around your plant is to place a humidifier near it.
Pests and Diseases
If you think your tree can’t get attacked inside by pests or diseases, you are in for a surprise. There are a lot of bugs that can hide indoors during winter. Watch out for spider mites.
These invisible to the naked eye spider-like creatures live on the undersides of the leaves. They leave webbing and tiny translucent round eggs. But don’t worry. Once you notice any of the pests spray the tree with insecticidal soap. It should get rid of most of the pests including woolly aphids, scale, aphids, mealy bugs, and more.
Fungal and other diseases are usually a sign that there is something wrong with the environment of your tree. If you notice root rot, you should probably water less and get better draining soil.
Decrease humidity levels and provide more air circulation if you discover a leaf fungal disease. The healthy tree rarely gets in trouble. It is when a tree is weakened, it gets attacked by diseases.
To help your tree fight, make sure to fertilize it during the growing season. And don’t use cheap fertilizers. You will get what you paid for. Cheap = low quality. Your tree will not get all the nutrients it needs and will be more susceptible to pests and diseases.
Growing bonsai indoors is a challenge because trees are designed by nature to grow outside. Your tree might last for a few years indoors, if you provide it with good conditions, but eventually will lose its health and vigor.
Once you notice signs of distress, it might be too late to save the tree. Also, do a little research before buying a plant.
Many dealers advertise outdoor trees as indoor plants just to make money. If you only want an indoor tree, get one of the tropicals that tolerate poor light and lower humidity. During warm months take it outdoors! It needs to regain its strength before winter.