It is essential to provide bonsai cultivated indoors with enough light to ensure their long-term health.
In a room with low light levels, as a natural response, plants will grow leggy and produce large leaves to capture more light. These large leaves and leggy growth is not good for the bonsai.
Can bonsai trees grow indoors without sunlight?
Yes. When natural light is too dim or unavailable, artificial lights can be used to grow bonsai trees indoors without sunlight. Aside from overhead lighting, place some lamps near the sides of the trees to provide adequate light for the lower limbs. Lower limbs will weaken over time if artificial light is only directed from the top of the tree, and the top branches will become too heavy.
Please refer to Artificial light levels required by various indoor bonsai trees to know exactly how much light you will need to grow a specific tree species indoors successfully.
Can bonsai trees grow under artificial light?
Artificial light can be used to successfully grow many indoor bonsai. In fact, many bonsai often do better in grow-lights. This is because their cultural needs may be more easily met in the controlled environment under grow lights than in the varied lighting conditions of windowsills around the home.
Ideally, this light garden provides a winter growing area for subtropical bonsai trees that have spent the summer outdoors in full sunlight, but for apartment dwellers with limited outdoor space, the lights can also be used year-round.
The total amount of light energy that a bonsai absorb depends on three factors: Color of light (frequency/spectrum of light) , intensity of light and length of the day.
- Light Color
It is known that plants do not utilize all light frequencies equally, but they are best able to absorb light in the blue and red spectrum. (Plants do not use green light efficiently, so it is reflected away, which is why plants appear green)
The blue light frequencies are used mainly for vegetative growth, for elongating stems, leaves, and roots, which are the main objectives of growing a bonsai. Using bulbs emitting mainly blue light promotes good plant growth as well as moderate fruiting and flowering.
Plants use red light frequencies to form fruit and flowers. Using bulbs emitting red frequencies triggers bonsai to make lots of flowers and fruit-which can actually weaken the tree. You should use mainly blue light frequencies with a little red to achieve long-term success in growing indoor bonsai trees. - Light intensity
When a plant is two feet away from a light source, it receives one quarter of the energy emitted by the light source (light energy decreases with the square of the distance from the light source).
In a nutshell, plants should be placed as close as possible to the source of light. Keep the bonsai safe, however, since some artificial light sources also produce a lot of heat. - Light Duration
In theory, the more a bonsai is exposed to light, the more light energy it will have at its disposal. Although it is not known if some plants require a rest period or not, but it is probably not a good idea to keep your lights on 24/7.
How much artificial light does a bonsai tree need?
Most indoor bonsai growers use artificial lights for 12 to 18 hours a day. The exposure of a bonsai to grow lights usually depends on the species of the bonsai tree as well. Determine your bonsai’s optimum day length by experimenting with your grow lights.
It is also important to keep in mind that some plants grow or flower depending on the length of the day or night. As an example, hibiscus flowers in the shortened days of the fall. On the other hand, plants like Serissa bloom almost continuously, regardless of the length of the day.
Types of grow lights available for bonsai trees
There are many grow light options available in the market. Lets look at some common widely used artificial lights and see their pros and cons.
Fluorescent Lights
It is possible to grow a wider variety of plants with fluorescent lights than with natural light on a windowsill.
Fluorescent tubes use relatively little electricity and have a low light output, so they must be placed very close to plants. It’s not a problem though, since plants can be almost touching fluorescent bulbs without being burned. Mostly these lights are places close to the tree, such as 20-30 cm above the plant.
For many indoor bonsai trees, cool white fluorescent bulbs or a combination of warm white and cool white fluorescent bulbs should be enough.
Fluorescent tubes used for fish tanks is also a good option for bonsai trees.
Fluorescent tubes emit much less energy at their ends than at their centers. Hence, it is essential to rotate trees so that they can benefit from the extra energy at the center of the bulb.
On a monthly basis, rotate the trees from the center to the end of the tube.
High Intensity Discharge lights (HID lights)
A high intensity discharge light promotes excellent growth and flowering, allowing trees that require lots of bright light to be grown indoors.
There are 2 types of HID systems available:
1. Metal halide lamps
Under metal halide lamps, plants grow significantly and increase their girth and leaf density. These are especially good for plants that are almost static and do not significantly grow or branch under moderate- to low-light conditions.
An area of four by four feet can be adequately lit by a 400-watt lamp, and an area of six by six feet by a 1,000-watt lamp. For trees that require plenty of bright light, metal halides work well.
Some of the drawbacks of metal halide lamps are:
- A metal halide lamp produces a considerable amount of heat. Hence trees should be kept at least one foot away from them to avoid burning leaves. Improved ventilation, however, can reduce the risk of leaf burn.
- Lamps and transformers must not get wet.
- There is usually only one transformer included with each metal halide light and it can only handle the wattage for which it was designed. For example, a transformer that runs at 250 watts cannot be upgraded to a lamp that runs at 1,000 watts.
- There is a humming sound produced by the transformers, which can be annoying in a quiet place.
2. Sodium lamps
Sodium lamps are usually not recommended for indoor bonsai trees.
These lamps produce a yellow colored light which gives the bonsai tree an odd aesthetic. Furthermore these lamps encourage etiolation (stem elongation), which is not desirable in bonsai culture.
These are red light source which will promote budding, flowering and fruiting. There are 2 types of sodium lights: high pressure sodium lights and low pressure sodium lights.
High pressure sodium lights are very hot and expensive to run. Low pressure sodium lights run much cooler. There are now efficient low pressure sodium lamps on the market that are even waterproof. However, I have avoided these lamps because of their yellow color.
LED Lights
You can also grow bonsai tree indoor with led grow light. LED grow lights are equipped with individual red, blue, and orange LEDs.
LED’s are relatively low power bulbs that must be kept fairly close to bonsai trees. However, LED lamps too close to the foliage may prevent the various light spectrum from mixing efficiently. This will lead to the foliage getting overexposed to just one light spectrum.
Ensure that the distance between the LED light and the plant is optimized according to the manufacturer’s recommendations.
There is no need for ventilation or cooling due to the fact that these bulbs do not produce heat.
These lights are relatively expensive than fluorescent lights. However, in the long run, the extra cost you incur will be recovered due to low energy costs.
How many hours of LED light for bonsai?
The duration of light a bonsai tree must be exposed to depends on the species of the bonsai tree. On an average, 12-15 hours of light exposure is generally practiced by bonsai growers. This depends on the power of your lamp also – less powerful lamp must be switched on for more hours. For an accurate light exposure time, you must know the natural habitat of of the tree species. Following is the general estimate of how much time an indoor bonsai tree will need light from grow lights:
- Trees from tropical rain-forest : Mornings are dry and hot. Young trees grow under the shadow of older trees. These trees have adapted to low lights and moist conditions. Leaves have thick cuticles and can accept dry air (central heating). 700 – 1000 Lux of light should be sufficient for these trees.
- Trees from subtropical forest: These forests are not so dense and sunlight can penetrate down to the earth. Subtropical trees go through 2 rainy seasons and 2 dry periods. The dry periods will lead to trees dropping their leaves. Example of such trees that can handle dry air: Ulmus parvifolia.
On the other hand, coastal subtropical forests might not go through such dry periods, and trees from here will require high humidity all year long. Examples of such trees that will need humidity all year: Sageretia, Ehretia, and Serissa.
The light requirements for subtropical plants are 1000-2500 Lux and the air humidity needs to be higher (50% minimum). - Trees from Mediterranean climate: These plants need bright light and dry air. Light up to 1000-5000 Lux. Examples: Myrtus, cistus, Acacia, Olea
- Trees from Subtropical Semideserts: Succulents and sclerophyllous trees from dry regions. Light up to 1000-5000 Lux.
What kind of light do indoor bonsai trees need?
The kind of artificial light you will need for your indoor bonsai depends on many factors such as : Bonsai tree type, space available, budget and light output. You can use fluorescent, LED or metal halide light sources. Following table can assist you in finalizing a light suitable for you.
| Type of Light | Light output | Purchase cost | Electricity cost | Efficiency | Space required | Life span | Cooling / Ventilation | Heat |
|---|---|---|---|---|---|---|---|---|
| Fluorescent | Low | Low | Low - medium | Low - Medium | Small - medium | Low | No | Low |
| LED | Medium | Very high | Low | High | Small | Very High | No | Low |
| Metal Halide | High | High | High | High | Large | Low | Yes | High |
How to use artificial light for indoor bonsai tree
As well as overhead lighting, place some lamps along the sides of trees to illuminate the trees lower limbs. In the long run, if artificial light is only directed from the top of the tree, the lower branches will weaken and the top branches will become too heavy.
Some growers hang lights on chains and tip them over to light the sides of the tree. Some people also direct light from the sides using a floor lamp.
It is generally advisable to suspend your lights about 10 to 32 inches (25 to 81 cm) above your plants, depending on the type of light source you use.
Fluorescent lights can be positioned 2-10 inches from the bonsai. Try and keep the bonsai near the center of the tube.
LED lights can be placed 10 inches from the bonsai.
High intensity discharge lights (HID) are very hot. A minimum distance of 12 inches (1 foot) should be maintained between HID and bonsai, along with good ventilation for dissipation of the heat. Or else the leaves will burn. If ventilation is not available, increase the distance to 20 inches or more.
Can I use a plant light for bonsai?
Regular plant lights simply produce light that is in the pale violet light spectrum. Regular plant lights are not recommended for bonsai trees. Instead you should use an artificial light source which approximates sunlight in giving a wide spectrum of colors of light. Choose lights that have daylight and warm light ranges.
Chlorophyll is responsible for the green color of leaves. Red, orange, yellow, blue, and violet light are absorbed by this pigment. The green component of light is mostly reflected by leaves (hence leaves look green to us). The violet colored “plant lights” are made keeping only chlorophyll in mind. However there are other pigments in leaves, such as carotene. Carotene which absorbs green light is not supported by violet colored lights. Because of this, light color lamps that simulate sunlight are more effective for bonsai trees.
Can I use Incandescent bulbs for bonsai
Typical home lighting, incandescent bulbs, is not recommended for bonsai growing at home. A typical incandescent bulb emits most of its light in the red spectrum and has a deficiency in the blue frequencies required by plants. The bulbs are also inefficient at producing light energy because much of the electricity is spent on producing heat. Bringing the tree close to Incandescent bulb is not possible because it will burn the leaves.
Can I use halogen bulbs for bonsai
Halogen lights are not suitable for indoor bonsai trees. These lights are also inefficient because most of the electricity is used up in the generation of heat and the amount of light that is produced is not enough. Plants cannot be placed close to them as the foliage will burn because of the heat. Hence compensating for the low light by reducing the distance between the tree and the bulb is not possible.
