What is a grow light?
A grow light is a specialized lamp that imitates or supplements natural sunlight to provide plants with the light they need for growth and photosynthesis. Depending on the situation, it can take on very different roles: In windowless rooms, indoor gardens, or enclosed plant display cases, it completely replaces daylight. In other cases, it serves as a targeted supplement when natural light is insufficient. Especially in winter, when days are shorter and light exposure is weaker, you can specifically support your plants with a grow light and safely guide them through the darker months.
Grow light vs. normal lamp
If you want to use a lamp for your plant, you should know that not every lamp is automatically suitable for this purpose. The crucial difference between grow lights and normal lamps lies in the wavelength range of the emitted light. For photosynthesis, plants need light in a specific spectrum of about 380 nm to 750 nm. Natural sunlight provides exactly this range – and grow lights are precisely tuned to this. Normal incandescent bulbs or standard household lamps hardly cover this spectrum or only incompletely. While they produce brightness, they do not provide the light that plants truly need. Using a normal LED as a grow light is therefore usually not very effective.
Light spectrum of the grow light: Which color for what?
There are many different grow lights. This is because plants utilize different wavelengths of light differently. To use your grow light correctly, you should therefore understand what is behind each color and which color is best used for what.
- Blue light: Promotes root growth and leaf development, ensuring a healthy start to the growth phase. Also particularly suitable for cultivating young plants.
- Red light: Primarily stimulates flowering and fruit development.
- Violet light: Means that the grow light contains both the blue and red parts of the light spectrum.
- Full-spectrum or white light lamps: Combine all these areas, mimic natural sunlight as closely as possible, and are universally applicable.
Which grow light for which plant?
Not only the light, but also the type of plant plays a crucial role in choosing the right grow light. What works best for green plants may not automatically be suitable for cacti or flowering plants. Here's an overview of the most important plant groups.
- Green plants like Monstera, Pothos, or ferns benefit most from a full-spectrum lamp with a high blue component, as leaf growth and root formation are primarily to be promoted.
- Flowering plants like orchids or anthuriums need a high red light component to stimulate flowering, which is why a full-spectrum lamp or a violet-glowing combination of red and blue is recommended here.
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Succulents and cacti primarily need intensity, which is why a bright full-spectrum lamp that mimics natural sunlight as completely as possible is the best choice here.
- Herbs and vegetables thrive best under a full-spectrum lamp with high light intensity. If you are seriously growing tomatoes or chilies, you should opt for special grow lights developed precisely for this purpose.
Using grow lights correctly – 5 practical tips
Buying a grow light is the first step. Using it correctly is the crucial one. With these seven tips, you'll get the most out of your grow light and your plants.
1. Distance to the plant
How close is too close? The distance between the lamp and the plant is one of the most common sources of error with grow lights. If the lamp hangs too close, leaves can burn. If it hangs too far away, too little light reaches the plant. As a rule of thumb: LED grow lights should be placed at a distance of about 20 to 40 cm above the plant. For weaker lamps, it can be a bit closer, for very strong models, it's better to be a bit further away.
2. Lighting duration
How many hours a day should the grow light be on? In most cases, 10 to 12 hours are appropriate. Plants not only need light but also a rest phase during which they can process the absorbed energy. If the lamp is left on for too long, there is a risk that the plant will be continuously stressed and grow poorly. This can be most easily regulated with a timer. It ensures that the lamp turns on and off at the same time every day, without you having to remember.
3. Light intensity
Not every plant needs the same amount of light. Most houseplants do well with about 1,000 to 3,000 lux, while succulents and vegetable plants often need significantly more. Commercial LED grow lights provide between 2,000 and 10,000 lux depending on the model, covering a wide range. If you have a dimmable grow light, you can adjust the brightness directly. Otherwise, the light intensity can be easily adjusted by changing the distance: the closer the lamp, the more intense the light; the further away, the softer.
4. Combination with daylight
If natural daylight is available, it should definitely be used. A grow light doesn't have to replace sunlight; it can simply supplement it. This is especially useful on cloudy days or during the winter months when light exposure is weaker. Set the lamp to cover the hours when natural light is weakest, for example, in the early morning or evening.
5. Acclimatization phase
Plants need time to adjust to new light conditions. This applies not only when you want to acclimatize plants to the sun, but also with artificial light. If you operate the grow light at full intensity from the beginning, you can overwhelm the plant. Start with a few hours per day and a bit more distance from the lamp, and gradually increase both over one to two weeks. This way, the plant can adapt gently and will reward you with healthy growth.
