3 main types of lighting are used for hydroponics:
- Compact Fluorescent Lighting (CFL)
- High Intensity Discharge (HID)
- Light Emitting Diode (LED)
HIDs are the most popular choice of lighting for hydroponics, although each type of grow light comes with its own advantages and disadvantages.
The Basics of Lighting for Hydroponic Systems
Before we start talking about the different types of lights for hydroponics, it’s important to have a basic understanding of how lighting works in hydroponics.
In nature, most plants need 6 to 8 hours of sunlight. Sunlight is more intense than artificial lighting, and as a result, plants need more light if they’re growing indoors. That’s why most hydroponic plants need around 14 to 16 hours of light.
Natural sunlight provides light from each part of the spectrum, although summer light is more on the blue end of the spectrum, while autumn light is more red and orange. In nature, the blue summer light stimulates plant growth- this light signals plants to move into the vegetative stage. The red and orange light of autumn prompts plants to enter their flowering and fruiting stages.
Because plants grown hydroponically, and indoors, won’t receive these cues from natural sunlight, you need to simulate them with the artificial lights in your hydroponic system.
Main Types of Lighting for Hydroponics
What about wattage?
Different types of lights deliver different levels of wattage. That can make it tricky to decide what light is best for your grow room.However, you can estimate how many watts you need in your grow lights with these rules:
If you’re growing plants that do better with low light, like leafy greens, you need 25 watts per square foot.
When you’re growing large plants that need more light, like blueberries, you need 40 watts per square foot.
For example, if you have a growing area (or grow room) that’s 5 square feet (or 5’ x 5’), you need 625 watts if you’re growing greens or other low light requirement plants.
With the same 5’ x 5’ indoor area, you’ll need 1,000 watts if you’re growing large plants with higher light requirements.
It’s important to make sure that light is distributed evenly throughout your hydroponic system. If light is too concentrated in certain areas, you may need to add a reflector to your lighting scheme. Reflectors are also a good addition if you have grow lights that illuminate a wide area, so you don’t waste any light that can be directed to your plants.
Another important thing to pay attention to is the heat your lights give off. Hotter lights need to be placed around 2 feet above your plants. Cooler lights can be placed as close as 8 to 12 inches above your plants.
If you’re not sure if your lights are running too hot, test it out for yourself: turn the lights on and let them run long enough to start warming up. Then, put your hand between the lights and the plants (just above the plants). If it feels uncomfortably warm, or even hot, it’s definitely too hot for your plants to handle.
Can you use incandescent lights to grow plants hydroponically?
You can certainly try, but it won’t work well. Unfortunately, incandescent lamps simply aren’t efficient enough (they have 5% efficiency), nor do they emit a spectrum of light that’s good for plant growth. Just by looking at this chart, you can see the difference in efficiency compared to other types:
Is LED or HID better?
Both types of light are great if you want to grow an indoor garden. While Metal Halide light is on the blue part of the spectrum, like fluorescent, HPS is on the red/orange part. An LED grow light also achieves both ends of the spectrum, whether it’s an RGB grow light, or you’re putting filters on your LED grow light. If you have a small indoor grow area, consider LED, which produces less heat. If you have a larger indoor grow area, you can choose LED, or a grow light combination of MH and HPS bulbs.
Which hydroponic grow lights are best?
Each type of grow light has advantages and disadvantages, as well as stages of plant growth they’re good for. If you want to avoid changing your lighting system as your plants mature, opt for HID or LED lights. To learn more about lighting in different growth stages, read this guide.