Should You Use Grow Lights for Your Bonsai?

Keeping your bonsai healthy and thriving involves the use of many different tools and accessories. One of those tools that beginner bonsai enthusiasts often feel unsure of is artificial grow lights. 

Many gardeners have different opinions about using artificial lights for supplementing your plants’ growth. 

Let’s look at everything you should consider if you choose to use grow lights for your bonsai trees! 

Does Your Bonsai Tree Actually Need Grow Lights? 

Each bonsai species has different light requirements, knowing how much light your bonsai tree needs and providing it with an appropriate environment is key to keeping your tree happy.

Like every other tree, bonsai trees from temperate climates naturally need a period of winter dormancy every year. During this period they don’t require much light so additional artificial light is not necessary. 

Tropical and subtropical trees, however, need sufficient sunlight all year round. Because of the UK climate it can be hard to meet both temperature and light requirements of tropical bonsai species. Particularly in winter, when it’s both too cold to keep them outside and there’s not enough natural light during the day. 

If a tree lacks enough light, you’ll notice a number of alerting signs including losing leaves, becoming more susceptible to pests or growing spindly shoots. This is when artificial grow lights for bonsai can be particularly useful.  

Using Grow Lights for Your Bonsai Tree

Artificial grow lights are a suitable solution to help indoor bonsai trees thrive during the winter months. A few hours of artificial light can supplement your bonsai’s growth and make up for the lack of sunlight. 

Here are a few of the factors you should consider to ensure the costs don’t outweigh the benefits. 

When and How Long Should You Use Artificial Light? 

Even when placed on a south/south-west facing window, your tropical or subtropical bonsai will only get a few hours of natural sunlight during the rare sunny days in winter. This is when you want to consider switching on a grow light for a few hours in the morning or after sunset.
The best option is to set your light on a timer so it automatically turns on and off. Your bonsai trees should be getting 12-15 hours of light per day, whether natural, supplementary or a combination of both. 

You can observe your bonsai to determine if it’s getting a sufficient amount of light. Depending on the exact species and the room temperature you might notice that your tree is growing healthy even during the winter months. Some trees might slow their growth over winter which is also fine. As long as your tree looks green and isn’t losing an excessive amount of leaves, it means it’s getting sufficient light. 

On days when the weather is overcast, or if your bonsai isn’t placed near a window, we’d recommend leaving the grow lights on for 12-15 hours a day. Again, having them on a timer is ideal as you wouldn’t need to remember to turn them on or off. Since your tree needs to maintain its natural day/night rhythm it’s not advisable to leave the lights on overnight. 

Below you can see a guide on the light intensity and illumination per day required by different types of bonsai trees. 

Bonsai Tree Type	Light Intensity	Illumination
Temperate Bonsai	700 lx	9 hours per day
Subtropical Bonsai	1,000 – 2,500 lx	12-15 hours per day
Tropical Bonsai	1,500 – 5,000 lx	12-15 hours per day

How to Use Bonsai Grow Lights? 

For optimal results the bonsai tree grow lights should fully illuminate your tree from above. You should allow a distance of 20-40 cm between the light source and the top of the plant. If you hang your grow light too high, there won’t be sufficient light reaching the tree.  

Choosing the Right Grow Lights

To ensure the healthy growth of your plant, the perfect grow lamps should have a high blue light component, balanced with a certain amount of red light component. Since the aim of artificial grow lights is to mimic sunlight as closely as possible, lamps with a full-spectrum colour are highly recommended. 

If you’re unsure whether a lamp can be used as a grow light, look for the number 1A or 1B on the label. There are many different grow lights for bonsai out there, but here are the most common types: 

• Full-spectrum fluorescent lights – This type of lights is particularly suitable for plant growth. They emit low levels of heat radiation, so you can hang them closer to the plant. The recommended distance is about 20-30 cm. Be careful not to hang them too high as their light would spread too widely.  

A downside of full-spectrum fluorescent lights is that they consume considerably more electricity than other alternatives and have a shorter lifespan. 

• LED – LED light bulbs and LED tubes are versatile which makes them perfect to use as grow lights. Since LED lights come in many different varieties, the key here is choosing the right colour temperature.  

Although this type of lights can be slightly more expensive than traditional fluorescent ones, in the long-term their low-energy consumption makes up for the initial costs. 

• Energy-efficient lights – Full-spectrum energy-saving lights are another suitable option because of their low heat emission. They’re normally compact in size which makes them ideal for illuminating individual trees. 

This type of lamps does fall behind LEDs, however, in terms of power consumption and lifespan. 

• Sodium vapour lamps – These types of lights are slightly outdated, but will still provide sufficient illumination. Although they can’t achieve the ideal spectrum for plant growth, they have high luminosity. 

The problem with sodium vapour lights is that along with light, they produce a great amount of heat. This combined with their high running costs, makes this type of lamps a less desirable option. 

Can You Use Incandescent Lamps as Grow Lights? 

Unfortunately, normal old-fashioned incandescent lights are unsuitable for grow lights. Their warm white light contains too many red components which isn’t recommended for healthy plant growth. Additionally, incandescent bulbs generate too much heat, which can be harmful for your bonsai. 

Find the Perfect Bonsai 

If you want to find the perfect bonsai tree to add to your collection, you’re at the right place! With the large selection of indoor and outdoor bonsai trees here at Bonsai 2 U, you’re sure to find the one for you. For more expert advice and useful information make sure to read check out our Care Hub.