Caring for an indoor Bonsai Tree

By Melanie Mathieson
Gardening Guru

Since this is often the time of the year that you start seeing bonsai trees for sale in floral shops and year-round nurseries, I thought it would be a good idea to provide some direction on caring for these unique little plants.
Bonsai, literally means Bon (tray) Sai ( HYPERLINK “http://www.essortment.com/all/bonsaicare_rwjp.htm” \l “#” plant) and is a way to grow many different kinds of plants in small containers, either indoors or outdoors. Growing plants in this manner began around 200 B.C. by the Chinese, was later adopted and developed into an art form by the Japanese, while North Americans discovered this gardening method about 50 years ago. Bonsai growing, which is gardening on a miniature scale, is considered an art form and is great if you have limited space.
Bonsai can be developed from seeds or cuttings, young trees or naturally occurring stunted trees transplanted into containers. Most bonsai range in height from 5 centimetres to 1 metre. Bonsai are not special hybrid dwarfs but ordinary trees or plants. Bonsai are kept small and trained by pruning branches and roots, periodic repotting, pinching off new growth, and wiring the branches and trunk so that they grow into the desired shape. Small leafed varieties are most suitable, but essentially any plant can be used, regardless of the size it grows to in the wild. In Japan, varieties of pine, azalea, camellia, bamboo, maple and plum are most often used. These are often the species we will find already in bonsai form in our local nurseries or floral shops. In our area, we will grow these plants as indoor specimens, but that does not limit someone from trying the art of bonsai in outdoor pots or their own garden. I have seen many shrubs and trees over the years in people’s gardens or in the wild that have that “bonsai look”. It may have been unintentional and was created as a result of neglect or poor growing conditions, but it can still be simulated in the wild.
When you purchase a bonsai from a local nursery or floral shop, they come already established in a pot, often moss, gravel or pebbles covering their soil. This is used to retain soil moisture and prevent soil erosion when watering as well as for good looks. If your pot didn’t come with this, feel free to add it. Your bonsai should be happy in the pot you purchased it in for quite some time but when the root system has filled the pot it will need to be repotted. The reasons for repotting are to supply your tree with fresh soil and to encourage a more compact root system. As a rule, most deciduous trees require repotting every two or three years, while evergreens only need to be repotted every four or five years. Since trees grow at different rates, this schedule will not always hold true, therefore, you should examine your tree’s root system each year to determine if it has become pot-bound. It is important to keep any care information that has come with the plant when it was purchased as it may have some important guidelines for this specific to the species that you purchased.
In most cases, the potting process should be performed in mid-summer and easy to carry out. The tree, along with all of its soil, should be removed from the pot. The outer and bottom most fourth of the tree’s root mass should be removed by raking the soil away, then pruning back the roots. Do not prune back more than one fourth of the tree’s root mass. After this, the tree can be placed back in its original pot or into another. The pot should have a screen placed over the drainage holes, a thin layer of small gravel for drainage purposes and then the new fresh soil deep enough to elevate the tree to its previous height in the pot. After placing the tree back in the pot, the area left vacant by the pruned root mass should be filled in with fresh soil. This fresh soil should be worked in around and under the root mass in such a manner as to avoid leaving any air pockets. After repotting, your bonsai should be thoroughly watered. This can be achieved by submerging the entire pot in a tub of water. Moss or other ground covers can be used to cover the surface of the pot to help prevent soil erosion when watering.
The ideal indoor location is in a south facing window with four to six hours of sunlight per day.. An east or west exposure is second best. A northern exposure will work, but will necessitate the use of “grow lights” to provide sufficient light to keep your bonsai healthy. A bonsai can be viewed best when it is placed approximately three to four feet high (eye level), such as on a table, wall or bench. Bonsai like higher humidity so place it in a shallow tray filled with a layer of gravel or pebbles, with water added. Do not allow the bonsai to sit in this water, just be elevated above it. Doing this provides extra humidity around the tree as the water evaporates and reduces the amount of moisture loss for the plant. Once positioned, it is often best to keep the bonsai in the same spot as you do not want to cause shock each time you move it. Also make sure the location you chose does not have wide temperature fluctuations throughout the day/night or seasons and is not subjected to drafts from doors, windows or the furnace/air conditioning kicking in.
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 daily. Water needs will vary with the size pot, type of soil and type of bonsai tree you own so evaluate each tree’s water requirements and adjust your watering schedule to accommodate it. It is a good idea to use a moisture meter (can be purchased at a garden supply store) until you get to know the requirements of your bonsai tree. Watering should be done with a watering can that dispenses the water in a soft enough manner as not to disturb the soil. Water should be applied until it begins running out of the holes in the bottom of your pot. Remember though that over watering is just as damaging to your bonsai as letting it dry out so make sure the soil is never soggy or waterlogged.
Since bonsai’s grow in such a small amount of soil it is necessary to replenish the soil’s supply of nutrients by applying fertilizer on a regular schedule. A general-purpose water-soluble fertilizer (20-20-20) for houseplants will do. Read the instructions carefully and find the mixture for general houseplants. Take this concentration and cut it in half of the recommended strength, then apply at least once a month, except during the winter months. Your bonsai will also respond well to foliar feeding. Take the fertilizer mixture and place it in a spray bottle and then apply by spraying the leaves/needles every other month.
Most of the true bonsai trees you buy have already been through their training period, thus requiring only periodic trimming and pinching to remain in miniature form. Training deals with the art of bonsai and should be thoroughly understood before undertaking. If you would like to train a bonsai from a large plant it is recommended that you thoroughly review the literature available today. As this is a complicated process it is not part of this column. In order to keep your Bonsai in good aesthetic form and in miniature size, you will need to trim and pinch back new growth periodically. Once new growth emerges, assess it to see if it needs to be pinched back to maintain the form of the tree. If not you can keep it and let it mature. If you need to remove it, trim it back to the origin of the new growth. Once the tree starts its growth cycle, never remove all of the new growth that sprouts, select what needs to be trimmed and then leave the remaining in order to sustain the health of the tree. Tropical and sub-tropical trees used for bonsai will require the most periodic pinching and trimming throughout the year but since different trees grow at different rates, it is necessary to evaluate each tree’s rate of growth and adjust your trimming and pinching to accommodate it.
Bonsai species are still susceptible to disease and insects even though they are inside the house. To keep some pests (and dust) from developing on the plant a shower in the sink or bathtub once every couple of months will help to keep it healthy. If you find pests, identify the pest and the follow the directions on the appropriate pesticide for treatment. Follow the directions carefully so you don’t damage or kill the plant. If you find pests on some of your other plants first always make sure you thoroughly inspect your bonsai, as these miniature plants grow under stressful conditions so a mild pest infection can wipe them out fairly quickly in comparison to other plants in the house.
With proper care, your bonsai will remain healthy, beautiful and miniature for many years to come. Since your bonsai is a living miniature tree, it will increase in beauty as it matures through the years.