Caring for Your Bonsai Plant

Bonsais are almost like pets, requiring attention and care. It requires continual feeding, watering and grooming just like a pet would. But unlike pets, bonsai won\’t be able to tell you that they are hungry. They may only tell you that when you see a withered look but you don\’t want to wait till then to do something about it. You will need to follow a strict regime to ensure that your bonsai stays at peak health.


There are generally two types of bonsais, those from the tropical area and the temperate climate bonsais. Serissa, ficus, or bougainvillea are tropical bonsais and are not adapted to freezing temperature. If you have tropical bonsais you will need to protect them against frost by bringing them indoors.

Temperate bonsais such as junipers and maples can survive lower temperatures. But as with all bonsais, they have a shallow root system which must be protected from the cold. Bonsais regardless of their type should be kept outdoors unless there\’s sufficient light indoors and lots of water.

If you live in a area with wintering months, bring in your tropical bonsais indoors while temperate ones can live in a protected frame (or any other protective set-up) with watering reduced to about once a week (check often for water requirement) and make sure the soil is layered with leaves to project the soil.


The bonsai should be turned every two weeks or so especially if you store them in a sheltered area where the light source comes from a certain direction. This is so that the tree will not grow out of shape towards the light.

If you have concrete flooring, make sure that you support the pot off the floor with wood blocks or bricks. Do not expose bonsais on concrete floor directly with sunlight for long periods. The heat generated off the concrete will warm up the soil in a bonsai pot and kill the roots with over heating.


The amount of water your bonsai needs depends on the type of soil that you use and the species of tree that you have. It also depends on the amount of leaves on the tree as well as the size of leaves and the tree. You should check on your plants regularly and it will take some time for you to understand how much water your plant needs as you care for them. Watering is important as it carries much needs hydration for your tree and provides a medium for the nutrients to bind to, to be utilized by the tree. Water also allows your plant to wash out excessive build up of salt and pushes out the spent gasses in the soil, allowing fresh atmosphere to go in.

Generally trees require more water in summer than in winter. Do not water the plants with a normal garden hose as this may erode the soil in the pot. Use a fine spray to ensure moisture reaches the soil and the tree. The surface of the soil is important (that\’s why bonsais can survive in such shallow pots) because it\’s the area where there are lots of gaseous exchange which is important to the plant.

Every once a week or so, soak the bonsai by placing the pot in a tub of water that is deep enough that it comes up to about an inch deep up the trunk. Leave about 2 or 3 minutes or until all the air bubbles have escaped the soil, then remove from the water.

Try watering early in the day as watering late in the day makes your plant susceptible to fungal attacks and slugs. Try not to water during mid day when it is hot as this may shock your plant into transpiration, which, inadvertedly, allows moisture to escape (think severe dehydration).

Don\’t water the flowers if your bonsais are flowering.


Fertilizers are not the main \’food\’ for plants. Fertilizers are like the vitamins in a diet. Therefore you shouldn\’t over fertilize your bonsai. There are three basic elements of fertilizer:

  • Nitrogen (N) – This works by increasing growth of leaves and stems
  • Phosphorus (P) – This helps the roots grow well
  • Potassium (K) – Encourages the growth of fruits and flowers.

Fertilizers with a relatively high Nitrogen content (at a ratio of NPK 12:6:6) can be used over spring to boost the tree\’s growth. Use a more balanced fertilizer over summer, while concentrate on toughening up the tree (on the roots) over winter. The age of your bonsai also plays a role on the type of fertilizer you use. Older bonsais require less Nitrogen and more phosphorus and potassium. Trees that are no longer in training require less nitrogen to stimulate for growth.

It is best to consult bonsai experts on the right ratio for your bonsai. Follow the instructions on the packaging carefully. Bonsais should be fertilized once every two weeks and should be done during only spring and early summer. After this initial fertilization, wait until autumn, then fertilize twice again (two weeks apart).

If you have a deciduous bonsai, do not fertilize in spring and wait until two weeks after the leaves have opened. In autumn, fertilize when leaves start to change color.


Below is a list of diseases that normally attacks bonsai, a brief description as well as what you should do should you encounter such problems. Always consult the local nursery for advise if you don\’t know exactly what to do.

Types of pest/diseasesDescription
Powdery mildew
  • a fungal infection that can be seen on top of leaves.
  • Can be caused by lack of air circulation on the leaves (due to watering late in the evening when the water does not have the chance to evaporate completely.
  • Fertilizers with too much nitrogen can also cause this.
  • Treat plant with natural anti-mildew fungicide
Downy mildew
  • Gray covering on the underside of leaves with yellow spots on top
  • Caused by lack of air circulation (high humidity in the air and high water content in the soil).
  • Relocate the plant to an area with better circulation
  • Spray with fungicide made from 1 tbsp of sodium bicarbonate + 2 tbsp horticulture oils dissolved in 1000 ml water.
  • The leaves turn yellow while the stem remains green
  • add chelated iron to its water supply
Sooty Mold
  • black soot-like deposits on the leaves or sides of bonsai.
  • Caused by fungus which is attracted to honeydew secreted by aphids
  • Treat with contact insecticide
Root rot
  • Caused by water-clogged soil.
  • Leaves become discolor and branches will fall off
  • Re-pot your bonsai and hold off fertilizing for about 8 weeks.
  • Keep bonsai away from direct sunlight
  • Fungal infection when humidity is high
  • causes brown/orange patches on the underside of leaves. These leaves will curl and drop
  • can also be caused by too much potassium
  • bacterial infection which happens when using pruning tools that have not been sterilized after cutting infected material.
  • Treat by cutting away infected area and dress the area with mastic to heal and prevent further infection
  • Always sterilize tools by running them over flame.
Mosaic (viral infection)
  • Symptoms include mottling alternate green and yellow stripes which highlight the veins on leaves.
  • You will need to destroy the plant that is infected to prevent infecting other plants in your garden

Bonsais are also susceptible to pests such as aphids, caterpillars, spider mites, whiteflies, mealy bugs and even ants. These pests can be remedied by successfully introducing beneficial insects, which reduces the need for insecticides. This method will see more success especially when the pests are detected early.

There is a long term commitment required when you have bonsai plants. These plants require. Caring for a bonsai plant is equivocal to a lifetime project. Some may even outlive you. It takes much nurturing and patience for your bonsai to thrive.

More reading:

Harry Tomlinson; The Complete Book of Bonsai

Peter Chan, Bonsai Masterclass

Deborah Koreshoff; Bonsai, It\’s Art, Science and Philosophy; Boolarong Publications, Brisbane.

Care and Maintenance Notes:

The role of Fertilizers in Plant Growth:

Bonsai – Diseases and Pests: