Traditional bonsai artists don’t like to talk about indoor bonsai. All bonsai are grown outdoors. Indoor bonsai enthusiasts were looked at with disdain. Indoor bonsai was made by the Western worlds. ALL plants that grow successfully indoors, in the West are from the tropics, where they grow in the sunshine with heat, humidity, wind, rain, and all of the weather patterns.
When you visit a bonsai garden, the “indoor” bonsai are almost always in a greenhouse environment. Though sheltered, this is not the same as a common living room. If you bring a bonsai from outside or greenhouse and place it indoors, it will suffer. There is no way around this fact. However, it can still be done; Here’s how:
How to successfully Grow Indoor Bonsai
The key is to growing bonsai indoors is to mimic conditions that are typically found in a greenhouse. If you have a heated sun-room or atrium, that is a great start, especially during the winter months. Keep in mind that these tropical trees will not survive the winter outdoors in non-tropical environments. There are several things to keep in mind when deciding to grow a bonsai tree inside.
Inside Lighting for Bonsai
Natural Light
Sunlight exposure will be the difference between your indoor bonsai thriving, barely surviving, or dying. The best thing you can do is place your bonsai tree near a window, preferably one that faces south. Consider moving it around the house. Different plants have different needs, but in general, no less than 5 hours of exposure to sunlight per day is important.
One good way to go about this is to first identify light levels (LUX) in the area that you intend on keeping your bonsai. The LUX can be measured with a light meter like this one found on Amazon for around $20.
Typical indoor bonsai trees require more light than other common houseplants. Generally, 4,000 – 5,000 LUX is a decent reading. Check the chart for more precise lighting requirements for indoor bonsai:
| Light Levels (LUX) | Light Category | Bonsai Species | Indoor Location |
| 20,000 – 50,000 | Very High | Succulents, Cacti | Porch, Patio, Deck |
| 10,000- 20,000 | High | Norfolk Island Pine, Ponytail Palm, Calamondin, Ming Aralia, Weeping Podocarpus | Porch, Atrium, Sun-Room |
| 3,000 – 10,000 | Medium Light | Schefflera, False Aralia, Ficus Benjamina (Weeping Fig), Oleander | South Facing Window |
| 500 – 3,000 | Low Light | Chinese Evergreen, Parlour Palm, Laurentii | Other Window |
| Under 500 | Dark | Not Recommended |
Artificial Lighting for Indoor Bonsai
High-Intensity Discharge Lighting (HID)
HID lighting has been widely used for many years for growing all sorts of plants indoors. They are great for growing indoor bonsai but can be quite expensive with both the initial cost and electricity usage. They come in two types of bulbs, High-Pressure Sodium (HPS) which looks warm in color and Metal Halide (MH) mimics the sun’s entire spectrum and is used for actual plant growth. Most people choose to use both types of HID lights in conjunction
Fluorescent Lighting
Fluorescent is our pick for the best type of lighting for growing bonsai indoors. They use about 25% the energy of incandescent lights and last over 10 times longer, according to energy.gov.
Fluorescent bulbs can be precise and you can adjust the color for different plant types or toe achieve specific results. For example, use the red light spectrum to encourage leaf growth, and shift to blue when it’s time to grow flowers. This is somewhat possible with other types of lighting, but not with the same precision and selection.
LED Lighting
LED stands for Light-emitting Diode. This type of lighting seems to be taking over these days due to being so convenient and easy to use. They do come with a high upfront cost but there are plenty of good options out there.
Watering Indoor Bonsai
How often do you water an indoor bonsai?
Generally, you can tell a plant needs watering when the surface layer of the soil begins to look dry. Spring and summer will normally require more water than the fall and winter. Check it daily and you will eventually learn the plant routine. It’s never a good idea to water without checking. Temperature, humidity levels, airflow, and sun exposure can all contribute to evaporation and absorption. It doesn’t rain at the same time every, so don’t water your indoor plants on a schedule.
How do you water an indoor bonsai?
You can water it with a watering can, but we recommend the immersion technique where you fill a container with water and dunk the entire base underwater, pot and all. This method will ensure that the soil and roots get truly saturated with water. Even if you don’t perform this method each time, it is always good to do it once a week or so, depending on the needs of your plant.
Read over our comprehensive Bonsai Watering Guide for more information on water both indoor and outdoor bonsai trees.
Indoor Bonsai Needs Humidity
Since modern houses are designed to keep humidity levels low. Even modern AC units have a dehumidifier built-in, so this can be tricky. Your bonsai (or checkbook) won’t mind at all if you turn the climate control off while you’re away. The good news is, certain rooms tend to stay more humid than others. Kitchens, bathrooms, washrooms might be a good option, although many don’t have windows. Consider moving your bonsai around to various rooms at night or throughout the day.
Invest in a good stylish humidity tray. Keep water in it, but make sure the water doesn’t reach the base of your pot, so it can’t seep in.
Be Careful of Heat for Indoor Bonsai
There’s nothing like a good heat source to evaporate moisture in the air. Keep your plant away from radiators, ovens, boilers, furnaces, and the like! Not only will these things substantially lower the humidity, but they may also scorch the leaves on your bonsai.
Be careful placing it to close to household items with motors and fans as well. Fans can put out a lot of heat in a small space that you might not notice. For example, an office bonsai tree on your desk at work, next to a computer’s exhaust fan.
It’s important to keep in mind that light sources can scorch or dry your bonsai as well. Most commonly, it’s high powered artificial lighting, but it can be the sun as well, so keep an eye on it.
Air Circulation for Indoor Bonsai Trees
You’re going to have your bonsai a long time (hopefully). One thing a lot of people overlook is the importance of air circulation. Photosynthesis requires fresh moving air to allow the undersides of the leaves to breathe. Otherwise, they will become caked with dust and mold and your tree will die. Fresh air is also required for water osmosis, which is how the water is drawn from the roots to the leaves. If this can’t happen, the leaves will not be fed and neither will your tree. Also, your soil and roots will stay moist, and eventually, root rot will set in.
The most obvious problem with a stagnated environment is pests. Scale, aphids, and spider mites are common for indoor plants. To learn more about pets, check out our Bonsai Pest Guide, which will cover the prevention, identification, and removal of bonsai pests.
Air Circulation improvement. Open doors or windows near your bonsai is always preferred when possible. This usually isn’t possible all of the time. It’s a good idea to try and keep your bonsai in larger rooms, especially if your home is not an open floor plan. Leaving the fan on often, even on low setting, will probably be enough to provide enough air circulation. You will want to spray your plant with water on occasion to clean the dust from your bonsai. Make it feel like it’s outside.
Feeding/Fertilizing
We cover general bonsai fertilizing extensively in our post Fertilizing 101. Check it out for general bonsai fertilizing purposes. Here we will cover indoor bonsai fertilizing basics. This doesn’t necessarily apply to outside bonsai.
It’s important to make sure that the fertilizer mixes are balanced. 4/4/4 or 6/6/6 mixes will be used for most plants. We recommend pellets every 2 months. Liquid fertilizer is fine if you prefer it, but you will need to make sure to fertilize twice per month with liquid, once every two weeks.
If you’re looking for a good indoor bonsai fertilizer, try Holland Basics organic 4/4/4. We have used it in the past and it was some of the best store-bought fertilizer we have used.
Keep Your Indoor Bonsai Trees Clean
One of the most forgotten care activities when it comes to indoor bonsai, is proper cleaning or as we like to call it, bonsai hygiene. Outside in nature, trees’ leaves are constantly being agitated by environmental actions like wind, rain, due, and changing temperatures. This helps to knock the dust and dirt from the bonsai and helps it to maintain good hygiene. Since these conditions aren’t present in your home (hopefully), indoor bonsai requires a little more tendering.
Get Rid of Dust on the Leaves!
Since all homes tend to accumulate dust, it’s a good idea to make sure it doesn’t accumulate on the leaves of your plant. This is often overlooked but it’s very crucial to the survival of your indoor bonsai. Transpiration is how water moves through your plant. Many don’t realize that all plants have tiny pores on the leaves that allow water vapor to exit. This is what causes the water to be pulled up from the roots through the entire plant. Dust will block the pores and stop the process. The roots will rot, the leaves will dry out, and your plant will die.
A feather duster can work but we recommend to spray a water mist on the plant about once or twice a week. Doing it at night will be best, as water will temporarily block the pores, sacrificing several hours of light if done during the day.
When using a feather duster, be careful to respect the styling of your tree. For example, if you are trying to obtain a windswept look, you will want to brush in the direction of the perceived wind. Never brush against the leaves or branches of your bonsai tree.
Clean the Top Soil
Over time, dust and debris will build up on the topsoil. This will need to occasionally be cleaned to prevent pests from being attracted to your bonsai. They make special tweezers, rakes, and brushes for this, but if you only have a few bonsai trees, common items like nail tweezers and a soft-bristle toothbrush will likely do the trick. Make sure you study the soil and give the entire layer a light brushing. If you see any foreign objects, just pick them off and throw them away. Serious bonsai artists use special tweezers, rakes, and brushes for this, but if you only have a few bonsai trees, common items like nail tweezers and a soft-bristle toothbrush will likely do the trick.
It’s very common for bonsai trees to have some exposed roots. These can become covered by a build-up of soil over time. You can brush the dirt away to expose the desired amount of root, just make sure you do it very carefully and with a soft brush so that you don’t damage the root to your bonsai tree.
Remove the Deadwood, or Don’t
Some of the more advanced bonsai artists will choose to use deadwood as an aesthetic. It can be created by various methods but sometimes it happens due to thinks like pests, root damage, or branch dieback. If part of your bonsai does die, then you will have to decide what to do.
Removing Deadwood from an indoor Bonsai Tree
The most common cause of deadwood is branch dieback. More often than not, this occurs because your branches didn’t get enough water or nutrition. This is the easiest form of deadwood to remove, just simply snip the branch with a pair of convex cutters. Make sure to cut well into the green living wood. This may seem like a bad thing, but consider it a warning and be thankful that your indoor bonsai tree is still alive! Now pay more attention to it.
Preserving Dead on an Indoor Bonsai Tree
If you decide to keep the deadwood on your bonsai, then you will first need to make sure to remove all areas of decay. You can then preserve the deadwood so it will not rot further. Depending on the tree type, there are different methods you will need to use for deadwood preservation.
Remove bark on the dead parts. Thoroughly remove all rotten sections of wood. A tiny amount of rot will contaminate the good wood left and the tree will continue to rot if it’s not totally removed. Some people are able to simply cut it off, but others use sandpaper and even power tools to make sure all of the decay has been removed.
Once all decaying areas have been removed from the bonsai, the deadwood can be preserved. It’s better to wait a few weeks and let the deadwood age. Most people prefer an old look to their bonsai, and deadwood looks much better after it cracks and becomes weathered. Be patient and keep an eye on it to ensure it doesn’t decay further during this time. Once it has the desired aesthetic, clean it again with a wire brush. Then it’s time to lock it in place and preserve the look.
Lime Sulfur
Clean everything with water. Then apply a lime and sulpher solution to the entire dead area. Let the solution drain into the hard deadwood, and allow 24 hours for the plant to dry. Do not place in the rain or rinse again, because it may wash away the solution.
This will give the deadwood a white color, but it will eventually weather into a very nice off white. Make sure to re apply this solution at least once per year.
There is another common method of deadwood preservation which includes encasing the wood in plastic. Alkaloid beads are placed in acetone to break them into a liquid. The alkaloid is then painted onto the deadwood and forms a clear plastic skin once the acetone evaporates. We do not recommend this as a long term method. Moisture still wicks from the roots into the deadwood, and after time the wood will begin to rot.
Indoor Bonsai Pests
We said earlier that cleaning the bonsai soil and misting it with water is the best preventative measure to stop pests on indoor bonsai, but here is how you can get rid of the pests once they do get on your bonsai tree, and eventually, they will.
It’s a good idea to occasionally look the plant over. Look for anything moving or that looks like it doesn’t belong. Notice the details. Most pests can be spotted with the naked eye and it’s better to catch them early and before a full-blown infestation begins. If you do locate a pest, then check out our Bonsai Pest Guide post, which will help you to identify and irradiate it.
Insecticides
Most pests are handled by pesticides that you can pick up at any garden center. They come in both organic and chemical formulations. The chemicals do work better but you should only use organic on indoor bonsai. If that doesn’t work, consider placing your tree outdoor temporarily (weather permitting).
Soap & Water
Insecticidal soap has many benefits over insecticides. It’s safer, less expensive, and growing in popularity. You can make your own insecticidal soap or find it in any garden center and most hardware stores. It’s easy to use as well, just spray it all over your plant and wait for the pile of dead bugs!
Dormancy
What is Plant Dormancy?
Dormancy is a time where the metabolic rate of the plants slow to conserve energy. The results are that they grow less and require less water and sunlight. This happens usually in the winter month, but it depends on the type. For example, tropical plants go dormant when the rainy season ends, since there is no true winter in their native environment.
Do Inside Bonsai Go Dormant?
Outside plant dormancy is brought on by annual environmental changes. Since the environment inside is essentially the same year-round, inside plants often do not go dormant. While some bonsai growers enjoy the extra months of growth, this is not good for the plant long term. As previously stated, the main thing to keep in mind is mimicking an outside environment. Bonsai need a rest period each year.
How to Make your Indoor Bonsai Go Into Dormancy
The bonsai may notice that towards winter, there is less and less sunlight. It will begin dormancy, so it’s best to wait until winter to put the bonsai into dormancy. Move the plant to a cooler and darker indoor area. Monitor it closely during this time, as you would anytime you put an indoor bonsai in a new location.
How to Bring A Bonsai Out of Dormancy
When the Spring rolls around, it’s time to bring the bonsai out of dormancy. Don’t just put it in direct sunlight. You want to gradually introduce it. Place the plant in indirect sunlight for a few days. Make sure to water it very well and give it a small amount of fertilizer to jump start it. Do not fully fertilize.
Can you grow indoor bonsai plants outdoors?
Yes, it’s a good idea to place your indoor bonsai trees outside during the summer, but they will need to be taken back indoors for the winter, especially when it frosts. The transition period may be tricky so keep an eye on it, and move back outside if necessary.
Can you grow outdoor bonsai trees, indoors?
Outdoor trees must be grown outdoors generally speaking. It is ok to bring your outdoor trees inside for some time, but watch it closely. Maples, for example, can often be brought indoors for 2-3 months at a time. If you do choose to try this, make sure that you place it next to a window and check the water levels often. Humidity helps!
What Are the Best Bonsai Trees for Indoors?
Chinese Elm Bonsai
The Chinese Elm is a very forgiving tree for beginners. It is easily trainable and you will be able to get some really great curvature. The leaves and foliage stay lush and beautiful until the winter. This is a deciduous tree, so be patient when the leaves do fall off. It’s only temporary.
Sweet Plum (Sagretia) Bonsai
This is another great bonsai to have indoors. Make sure to put it in a window that has the full-morning sun and maintains shade in the evenings. Especially keep it indoors if the temperature is under 60º F. This plant will need to be placed into dormancy for about 2 months around the winter solstice.
Buddhist Pine Bonsai
(Podocarpus macrophylla) one of the few tropical pines, the Budda pine is native to several mountainous regions. All pines are evergreen but this one doesn’t do well in cold environments and loves the warmth, making it a great indoor bonsai tree.
Japanese Holly Bonsai
(Ilex crenata) Originally from East Asia, the Japanese Holly is an extremely popular bonsai tree. We consider it more of a hybrid indoor/outdoor bonsai tree. It will need a cooler space in the winter months and won’t mind being outside until it frosts. It needs a lot of sunlight.
Kumquat Bonsai
Native to South and Pacific Asia. You will want to use the most light possible for this tree, especially during the summer months. Consider putting it outside in the full sun. Always bring indoors for the winter, as soon as a chill sets in. When indoors, leave in a humidity tray with gravel at the bottom. It will require fertilizing every year.
Ficus Bonsai
This is a good choice for your first indoor bonsai tree or first bonsai tree in general. They do well in low light areas as well as low humidity. They are beautiful on the top as the bottom, as they can grow many roots above the soil. Place in a shallow pot where the roots can be seen.
