Want to learn more about Grow lights
Get individual care schedule and reminders for your plant with our app Planta. Never kill a plant again!
Grow lights are a perfect way to supplement your plants when they can’t get adequate natural light or to keep your plants thriving during the darker seasons of the year. It’s important that you’ve set up the grow light accurately according to the product you’re using and the plant you have.
What are Grow Lights?
Grow lights are artificial lights that you can use to supplement your plants when they don’t get adequate natural light. It will help the plant photosynthesize so it can keep growing and thriving even if it’s placed far from the window or if the season has less hours of daylight.
When can you use grow lights?
Grow lights can be used any time of the year. They are especially helpful in lower light areas and at darker times of the year.
If you don’t have the right amount of light for your plants you might need to set up grow lights to keep your plants happy. There are many factors that can reduce the light available in your home. It could be due to the direction of your windows, the natural light being blocked by surrounding buildings, the plant’s distance from the window, a climate with darker seasons/less daylight or to give your cuttings and seedlings some extra support.
- If your windows are already cramped with plants you can use grow lights to create more growing space!
How to set it up!
It’s important to set up your grow lights correctly to give your plants the best chance to thrive. Using the right type of light source, keeping the light at a correct distance and having it on for a correct amount of time are important factors.
Here's the short version:
Type of light: Specialized grow lights, LED-bulbs, -strips or -tubes or COB lights
Color spectrum: A combination of red and blue light or a light source with as high Kelvin as possible (preferably 4000 - 6500K)
Amount of time: Between 8-16 hours but 10-14 is preferred for most plants
Distance: 8-18 in (20-50 cm) is recommended depending on the intensity and the coverage of the light.
Direction: Directly above the plant
- If you want to learn more you can keep on reading!
Here’s our full guide on how to set up your grow lights!
Types of light sources
Strips, LED bulbs, LED tubes, Full spectrum platforms. They come in all shapes, colors and sizes and there’s a whole jungle of different grow lights and other suitable lights on the market.
You can decide if you want to buy a ready-made product that’s labeled for use as grow lights for your plants or source bulbs, strips or tubes with suitable parameters at your local hardware store.
LED Bulbs and LED Spotlights
These types of light sources are usually best suited for individual plants as they have a narrower spread of light. Larger plants often need several individual light sources to get an even spread over the foliage.
Strips and LED tubes
These light sources are great when you want to give several smaller to medium sized plants additional light. Mounted in a cabinet or shelf you can grow plants even in places lacking natural light. They are also great when sowing seeds early in winter or spring, for planting outside later in the season.
COB stands for Chip-on-Board, and is a type of grow light that’s been growing in popularity. This type of LED light is usually for professional use and emits an extreme amount of light compared to most grow lights you will find at a local store. They often cost a lot more, but will illuminate a large area with intense light. They are most valuable when illuminating a large collection of plants. This type of light source is a great option for the hardcore plant collector. They often use a lot of electricity when operating and risk burning sensitive species.
Amount of light and colors
The amount of light you’re going to need depends on what function the grow light is going to serve. Is it intended to prevent damage due to low light levels during the winter? Then a weaker light source might be enough for you. If it’s to promote further growth during a dark season, then you’re going to need a source emitting higher amounts of light.
The color of the light is also important. Measured in kelvin (K), the color temperature of the light source tells the amount of the different wavelengths the light consists of. A warmer light contains a lot of yellow and red light, while a cooler light contains a lot of blue. Plants can only benefit from red and blue light, preferably heavier on the blue part.
A couple of years ago, magenta lights became popular. These LED lights often consist of diodes emitting light only beneficial to photosynthesis (red and blue diodes). These are great for plants, but most people don’t like this intense color. It is definitely worth investing in a light that both the plant and the plant owner appreciates.
Amount of time
All extra light is beneficial when your plant doesn’t get adequate natural light but to ensure a thriving plant and good growth it’s important to provide it with a good amount of light throughout the day.
The recommended amount of light exposure time is 8 - 16 hours a day. Where 8 is minimum and 16 is maximum. 10-14 hours a day is suitable for most plants and will keep them thriving and more actively growing throughout the year– with some exceptions of course.
- A few plants are dependent on a darker season to be able to produce flowers. Poinsettia and Flaming katy are two examples of plants where the dark period is essential to bloom each year.
Avoid leaving grow lights on for 24 hours a day as it can starve a plant from fully utilizing a rest period that it needs to grow. (It will also cost you more, and isn’t as environmentally friendly.) The best way to keep track of the number of hours is to connect your grow lights to a timer. You can also set an alarm on your phone or you can turn the lights on when you wake up and off when you go to bed.
- Plants need to rest and are depending on a day and night cycle, just like us humans. So make sure they get a well deserved night time every day.
First photo is showing a grow light kept at a good distance. Second photo shows a lamp that's too far from the plants and the last photo shows a lamp that's too close to the plants.
The distance from the plant is just as important as the amount of hours the light is switched on. If a strong light is placed too close, it might expose the plant to too much light and in rare cases it could even burn the foliage. If the light is placed too far from the plant the light exposure decreases and may be insufficient for the plant. Moving the light further will cover a bigger area but decrease the exposure so you need to find a good balance between light exposure and coverage of the foliage.
Most grow lights will come with instructions regarding how far away and where to place it.
If your light doesn’t have any instructions or if you aren’t using specialized grow lights a distance of 8-18 inches (20-50 cm) is recommended depending on the intensity and the coverage of the light.
A plant produces leaves to absorb light and to perform photosynthesis. If leaves and branches don't get adequate light they will use more energy than they are producing, becoming useless to the plant. Make sure that the light is covering all of the foliage of your plant to ensure good growth and prevent leaves and branches from dying due to lack of light.
Plants generally grow towards the light. That’s why you get tilted plants when they are grown indoors and only have a window as a light source. The best placement of your grow light is above the plant.
If you place the light below the plant or at an angle, your plant may grow unevenly and parts of it may die back.
These photos shows when the grow light is placed at a bad angle or doesn't cover the entire plant properly.
Troubleshooting your grow lights
Practice makes perfect and you might need to adjust the grow light until you get it right. If watering, fertilizing and all other care you give your plant are correct, you might need to have a look at the grow lights. To help you find out what your plant is telling you here are some tips and tricks on how to read the symptoms on your plant:
Stretched growth, lighter green color, yellowing leaves or losing its lower leaves
This may indicate that your plant isn’t getting enough light. You might need to supplement with more light sources, move the light closer to the plant or increase the amount of time you have the light on for.
Bleached leaves, pink and red hues, curled up leaves or burn marks
This may indicate that your plant is getting too much light. You can try to move the light farther away from the plant or decrease the amount of time you have it on for.
- If your plant have been kept in a dark spot for a long period of time, it may be necessary to slowly adjust your plant to the increased light to prevent it from getting scorched.
Can grow lights burn your plants?
Yes it is possible but not very common when using most common LED Grow lights. If placed very close, LEDs can burn leaves but it’s more common to get burn damage and dry leaf edges due to using fluorescent light tubes. This is mainly from the heat they produce.
Can I use regular lamps?
Yes, even if products sold as grow lights are tested to ensure they give your plants adequate amounts of beneficial light, you can use “regular lamps” too. There are however things to look out for when using a lamp not intended to be a grow light. High lumen, and Kelvin around 4000 - 6500 is good to aim for. This usually ensures a good amount of the light produced by the lamp. Unfortunately brightness is not a guarantee of the best quality light for your plant.
Lumen, Watt, Kelvin, Lux, FQ and PAR. What’s the difference?
These are all different units of measurement connected to measuring light. Note that it might be worth looking for a grow light that will produce a high PAR value (or lumen) in relation to W to get a cost effective operation in the long run.
Lumen (lm), is the unit for measuring the total amount of visible light emitted by a light source. This will show the level of brightness your grow light will have. Note that this doesn’t take into account the length or angle of spread. Lux is a measurement of lumen per area.
Watt (W), is the unit of power. It will show the electrical consumption and can, to some extent, indicate how strong the light source will be. It is better to look at the lumen value to read how bright the light will be. Note that LED lights consume a lot less electricity than fluorescent lights or halogen lamps.
Kelvin (K), is the measure of color temperature of light sources. A lower K indicates the light source will emit a warmer light, while a higher K indicates a cooler light. Most light sources better suited to plants are within the range 4000 - 6500K.
Lux (lx), is the unit of illuminance per unit area. 1 lux equals 1 lumen per 1 square meter.
Foot candle (fc) = is the unit of illuminance per unit area. 1 foot-candle equals 1 lumen per 1 square foot.
PAR (Photosynthetically Active Radiation), is the unit of measuring all light beneficial to photosynthesis in plants. A good quality grow light should indicate the tested PAR value. This is usually not a tested value in regular light sources.
Can a plant get too much light?
Yes, but it’s unlikely when using only Grow lights. Different species have different requirements of the amount of light they need. A species that doesn't tolerate too much light can get bleached leaves from strong light sources placed too close. If that happens, you can try to move the light farther away from the plant or decrease the amount of time the light is on for. In most cases a good quality light source at the proper distance equals a spot with lots of indirect natural light. This is a level most plants enjoy.
Does the color matter?
Yes! Light color is measured in Kelvin. The Kelvin tells us the proportions of different wavelengths in the light produced. A Kelvin value at around 4000 - 6500 usually means the light source has an acceptable balance between red and blue light, which are the wavelengths beneficial to plants. Green and yellow light don’t help the plant grow at all.
Does the price matter?
Not necessarily. You can find cheaper options by searching for light sources not officially meant for growing plants. The amount of beneficial light can vary a lot between lamps though. Professional and tested grow lights may cost a bit more, but they often come with a spectrogram over the distribution of what wavelengths it produces. If not, they should at least indicate PAR.
Are grow lights just as good as the sun?
No, most grow lights don’t come near the intensity of direct sunlight. Grow lights should be approached as complementary to natural light when growing sun loving plants. When it comes to plants that do well in a lot of secondary light though, a good grow light can sometimes equal such a spot.
Are grow lights suitable for all plants?
Plants that require full sun to be able to thrive and grow healthy won’t settle for just grow lights. They will need a source of natural light too and you should only use grow lights as a supplement. This includes plants such as cacti, citruses, pelargoniums among others. Low light plants will on the other hand do just fine under grow lights only, but as mentioned above grow lights will never be as good as the light produced by the sun.