Bonsai trees can be difficult to care for, even for an experienced indoor gardener. Their needs and the types of problems that can occur are significantly different from those of many common houseplants. Additionally, depending on the species, bonsai trees can be delicate and vulnerable to multiple types of pests. When a problem does occur, follow these steps to ensure the health and longevity of your miniature tree.
Step 1: Closely Examine The Plant
Before doing anything else, see if you can determine the source of the issue. Look over your bonsai plant, taking time to examine each leaf and branch. Here are some common symptoms to look out for:
- Fuzzy spots on trunk or leaves
- Any insects or insect eggs
- Yellow, wilted or dry leaves
- Red spots
- Shrunken branches
The proper course of action depends on which symptoms are present. If you spot a woolly fuzz, it is likely that your bonsai is infested with fungus. Generally, a small amount of rubbing alcohol carefully applied will take care of the problem.
If you spot any insects, remove them immediately. Try to either save a specimen or take a photo so that you can accurate identify which species is present. Most insect pests can be removed by the application of insecticide. Make sure to carefully read the instructions on any product before application to ensure that it is safe for use with bonsai trees.
Red spots may indicate the presence of spider mites. In that case, insecticides will generally be ineffective. The best strategy is to carefully apply a small stream of forceful water to clean the mites off the plant. Make sure to remove every single insect present. Closely examine the base of the bonsai trunk for mites just under the soil.
If you remain unsure what the source of the problem is, continue to the steps below. If you have tried one of the above remedies and the issue persists, also go on to further steps.
Step 2: Repot And Trim The Roots
Gently lift your bonsai tree from its pot. Place the plant on a flat surface that is clean and sanitary. Brush away the loose dirt from the roots.
Look over the roots. Be on the lookout for any roots that are wilted, mushy, wet, or black. Healthy bonsai roots will be a color similar to the trunk. Black roots are likely diseased.
If you do find any unhealthy roots, use a sterile pair of scissors to trim them away. Do not remove more than a third of the root-system. Make sure that you do not touch healthy roots with a blade that has cut infected areas away, or you may spread the disease to further areas of the plant.
Step 3: Find A New Pot
Choose a new container for your tree. The old one may be contaminated with the disease or pest. Make sure that the new pot is clean, well-draining and of an appropriate size for the plant. The depth of the container should be approximately equal to the diameter of the tree’s trunk. Typically, you will want to choose a new pot that is slightly larger than the old one.
Wipe out the new pot with a clean piece of cloth dipped in wood alcohol. This will sanitize it. Allow the pot to air dry completely before preceding to the next step.
Step 4: Add Moss And Soil To The Pot
Place clean, high-quality sphagnum moss at the bottom of the pot. Fill to about one third of the depth. The moss will aid in both protecting the tree from disease and in growing new roots.
Gently center the tree in the pot, making sure the roots are well spaced and have adequate room. Fill the remainder of the container with potting soil.
The exact mix of soil to use depends on the species of your tree. Generally, bonsai trees prefer soil with low levels of phosphorus and nitrogen. They also thrive in loams that are relatively sandy, so add some sand in with the soil. Do not re-use the soil from the old container, as it may be contaminated with bacteria or insect eggs.
Step 5: Prune The Branches And Leaves
Make sure that your scissors or pruning shears are clean and sterile. Carefully examine the tree for any discolored, wilted or dead branches and leaves. Remove them gently with the shears. Tweezers may be necessary for some species.
Pruning serves two important functions. First, it removes any infected or diseased parts of the tree. This gives the healthy parts of the tree a better chance to recover. Second, it allows the plant to better focus its energy on the growth of strong areas. In some cases, pruning may also improve access to sunlight and air circulation.
Step 6: Place Your Tree In A New Location
If your plant has been struggling, chances are good the old location was less than ideal. It is also possible that a return to its old environment will re-expose the tree to the same pests.
Be sure to choose a sunny spot. A bonsai tree needs at least six hours of sunlight per day, and ideally eight. The location should also have a good circulation of air. The levels of humidity present should be moderate. Both too much and too little moisture in the air can cause health problems for bonsai trees.
The final factor to consider is temperature. Moderately warm areas are best. Because of the delicate balance required, it is usually easiest to keep bonsai trees indoors where you have more control over the environment.
Step 7: Water Your Tree
Use water that is room temperature to avoid shocking the plant. Continue to pour water until liquid flows out from the drainage holes. After that, water only infrequently.
Check the soil before re-watering. The soil should be allowed to become considerably drier before watering again, but it should never be completely dry.
Some species of bonsai trees will need to be misted daily for proper humidity.