Bonsai is the art of creating natural tree forms but in miniature. This popular art form has its origins in Japan and China where it has been practiced for centuries.
'Indoor' Bonsai is a relatively new concept. In the past, outdoor bonsai may have been displayed temporarily indoors for a couple of days. They still are today, at bonsai shows and horticultural events.
The popularity and demand for indoor bonsai has grown dramatically in recent years. It has been actively promoted by larger garden center and supermarket chains looking to cash-in on this trend. It is especially attractive to people that live in housing that lacks any outdoor space.
Indoor Bonsai Basics
There are a few basics which anyone new to indoor bonsai should be aware of.
Remember, a healthy indoor bonsai must to be able to cope with fluctuations in temperature and humidity. Central heating and ventilation systems not only create fluctuations in temperature but also reduce humidity, causing your bonsai to dry out quickly.
Placing an indoor bonsai on a windowsill in direct sunlight will be very bad for the tree. Placing an indoor bonsai where it receives very little daylight will also be very bad for the tree.
Under-watering your indoor bonsai will result in it drying out which will be very bad for the tree. Over-watering your indoor bonsai will result in root rot which will also be very bad for the tree.
Deciduous or Evergreen?
Deciduous trees naturally lose all or most of their leaves in the winter. Often the leaves will change colour, turning yellow, orange, red or brown before they fall off. The leaves will re-grow again in the spring.
Evergreen trees retain their leaves throughout the year but continually replace their old leaves with new leaves as they grow. The leaves of evergreen trees may change colour over the winter months due to changes in light levels and temperature.
Winter Rest Period
In winter, we switch the central heating on just when your bonsai is expecting a cool/cold winter rest. Just like humans, if your tree doesn't get a chance to rest, it may start to sulk, weaken over time, and ultimately result in a slow, premature death.
Indoor Bonsai Care Instructions
Bonsai are grown in pots and are dependent on you for their care. With proper care and attention, your bonsai will remain healthy and beautiful for many years to come.
Spring, Summer and Autumn
When nightly temperatures no longer fall below 5 C, your bonsai should be placed outside, in a sheltered spot. It should be positioned where it will receive sufficient morning sun and afternoon shade.
Because bonsai are grown in relatively small pots, they are liable to dry out very quickly, putting your bonsai at risk. Make sure you adapt your watering regime to the weather conditions and take notice of increasing intensity of the wind or sun.
A bonsai can be viewed best when it is placed approximately four to five feet high on a table, shelf, or bench.
Once nightly temperatures begin to fall and approach 5°C, it is time to bring your indoor bonsai inside. The ideal indoor location is on a windowsill facing south. An east or west exposure is second best. A northern exposure will work but will require the use of grow lights to provide sufficient light to keep your bonsai healthy throughout the winter. Four to six hours of sunlight per day is ideal.
Remember when closing curtains that the temperature on the windowsill can drop considerably compared to the rest of the room.
The watering of your bonsai must never be neglected. Apply water when the soil appears dry. Never allow the soil to become completely dry. If your bonsai is receiving full sun, it may be necessary to water once a day. This may vary depending on the size of the pot, type of soil and species of tree. Evaluate each tree's water requirements and adjust your watering if required. Alternatively, use a moisture meter until you get to know the requirements of your tree. Water in a way so as not to disturb the soil. Water should be applied until it begins running out of the holes in the bottom of your pot.
During the cold months, when your bonsai is inside, we recommend placing it in a shallow tray filled with a layer of gravel with water added. This provides extra humidity around the tree as the water evaporates and reduces the amount of moisture lost to central heating and ventilation systems.
Bonsai are grown in small pots, so it is necessary to feed your tree if it is to remain healthy. Any general-purpose liquid fertiliser is fine and can be purchased at garden centres. We suggest that fertilisers be used at half their recommended dosage. It should be applied at least once a month except during the winter.
Bonsai respond well to foliar feeding... i.e feeding via the leaves. A water-soluble fertiliser is applied every other month as a liquid spray on the foliage.
Training and Styling
This brief explanation of basic care does not cover the continued training and styling of your tree. Training and styling is the most important part of keeping bonsai.
Trimming and Pinching
Trimming and pinching help to keep your tree small, and maintain, and develop its shape as it grows. Pinch and trim back the new growth. Tropical and sub-tropical trees used for indoor bonsai will require periodic pinching and trimming throughout the year. Since different trees grow at different rates, it is necessary to evaluate each tree's rate of growth and adjust your trimming and pinching as required.
Pests and Diseases
Your bonsai tree can be treated for pests and diseases the same as any other tree or plant. If you discover any pests or diseases, ask someone for advice before treating your tree. It is always wise to act sooner rather than later. The longer you leave a problem, the more likely it may cause harm to or kill your tree.
Repotting must be performed periodically on all bonsai when their root system has filled the pot. The reasons for repotting are to replenish the soil, encourage a more compact root system and ensure the tree has access to enough water and nutrients to continue to stay healthy.
Most deciduous trees require repotting every two or three years. Evergreen trees only need to be re-potted every four or five years. In most cases, the potting process is easy and safe if performed carefully and at the right time of the year. Indoor bonsai should be re-potted in mid-summer.
The tree, along with all the soil should be removed from the pot and the pot should be thoroughly cleaned and left to dry. A portion of the outer and bottom root mass should be removed. This is done by carefully raking the soil away, and then pruning back the roots. Prune back no more than one-fourth of the tree's root mass using a sharp pair of scissors or secatures. The tree can then be placed back in its original pot or into a new pot of a similar size. The pot should have a mesh screen placed over the drainage holes to prevent the potting mix from escaping. Then a thin layer of fine gravel is placed in the bottom of the pot to provide good drainage. On top of this layer of gravel placed some of the new potting mix, sufficient to elevate the tree to its previous height in the pot. After placing the tree back in the pot, start adding the new potting mix. This fresh mix should be worked in, around and under the root mass to avoid leaving any air pockets. A chopstick or similar implement is ideal for this. Once complete, your bonsai should be thoroughly watered. This is best achieved by slowly submerging the entire pot in a bowl of water and waiting until all the air bubbles stop rising to the surface. Then allow your tree to drain thoroughly.
Indoor Bonsai Trees
Bird Plum or Chinese Sweet Plum
Sageretia sp. - Evergreen.
Syzygium sp. - Evergreen.
Podocarpus sp. - Evergreen.
Ulmus sp. - Deciduous.
Ilex sp. - Evergreen.
Ligustrum sp. - Evergreen.
Ficus sp. - Evergreen.
Carmona sp. - Evergreen.
Olea sp. - Evergreen.
Pepper Tree or Sichuan Pepper
Zanthoxylum sp. - Evergreen.