It’s generally accepted that more light = more growth and to a point that’s completely true. What it doesn’t tell you is that there are lots of different types of light and your plant only uses certain spectrums.

The visible spectrum

Think of a rainbow - the colours that you see in a rainbow make up the visible spectrum. When you see a rainbow, what you are actually seeing is normal sunlight refracted into its separate wavelengths by the raindrops in the air. This effect separates the white light into all the colors we can see. Red, orange, yellow, green, blue, indigo, and violet make up the color spectrum. The visible spectrum contains light that can be seen by humans, yet there is other light that we cannot see. The light that cannot be seen with the unaided eye includes far-red and ultraviolet rays, both of which can affect plant growth.

What does the visible spectrum have to do with plants?

Plants must have light to grow and survive in their environment. The plants specifically use light to make their food in a process called photosynthesis. The light is absorbed by the green pigment chlorophyll, which is located in the leaves of the plant. The actual colours in the visible spectrum that the plant absorbs and uses for photosynthesis are red and blue. The plant reflects green light, and that is what we see when we look at a green plant. Green light is not the only reflected light. For instance, far-red light is also reflected. Far-red is just outside the visible light spectrum. It is not visible to the human eye, but can be sensed by the plant. Far-red wavelengths are important to the plant because of the competition factor in nature. A plant can 'SEE' when there are other plants close by because of the increase of far-red wavelengths the other plants reflect. This will then signal the plant to make the necessary adjustments within their system to try to outgrow the others around them since they are competing for sunlight and other resources.

Why should I care?

All sounds very interesting huh? But why should you care? The reason that you need to know this is that because as an indoor gardener you are trying to recreate the power of the sun with your grow lights – and if you’ve got the wrong light then your plants aren’t going to do very well at all. For example, the effect of far red light (above) is not always a good thing – yes it will stimulate the plants to attempt to outgrow each other, put in a practical application this leads to leggy plants – not something you want in a grow room with limited headroom. With this in mind, the importance of plant spacing suddenly becomes much clearer – plants that are crowded will have very little side growth and will stretch towards your lamp because of reflected far red light. Space them properly and you will have less of a problem.

Creating the “right types” of light

As we said earlier, the actual wavelengths that are used by your plants fall into the blue and red spectrums. Blue light for vegetative growth and red light for flowering growth. There is ongoing development by NASA into creating pure forms of the exact wavelengths of light required for growth using LEDs, but as yet these technologies are prohibitively expensive and are still under development. This leaves us with a few options to use for our grow lamps.

HID Lighting

HID or High Intensity Discharge Lights are the lamp of choice for most indoor gardeners. There are three main types: Metal Halide, High Pressure Sodium and finally Spectrum Adjusted High Pressure Sodium (Sodium Grolux). Each type requires a ballast to ignite and power them.

Metal Halide (MH) Lighting - Metal Halide lamps are used for vegetative growth as they give off light in the blue spectrum. They give off a high level of heat which can cause problems in some grow rooms that do not have sufficient ventilation or air exchange.

High Pressure Sodium (HPS) Lighting - HPS lamps are used primarily in flowering as they give off light mainly in the red spectrum. That said, it is possible to use them throughout your grow (for vegetative growth too) as they will still produce a result.

Spectrum Adjusted High Pressure Sodium Lighting (Sodium Grolux)

The lamps that we recommend to most growers and those which give the best possible “one lamp per grow” result are Sodium Grolux Lamps. These lamps are effectively the same in design and operation to a standard HPS lamp but have been adapted to provide more blue light. This means that they perform much better when blue light is required (vegetative growth) whilst the loss in red light (flowering) is negligible.

Fluorescent Lighting

Fluorescent lights give of considerably less heat and use a lot less power than HID lights but also produce a lot less usable light for your plants. There are generally two type of fluorescent light, each one available in cool white/blue or warm white/red varieties. These two varieties allow you to give your plants the correct red or blue spectrum light dependant upon whether they are vegetative or flowering growth. The two types available are standard fluorescent tubes (as used in the BrightWing Propagation light) or compact fluorescent lamps (CFL) such as the Eco-Light.

In general, we would advise against using fluorescent lights as your main grow lights as they produce significantly less yield than HID lights. That said though, there are many times where it is impractical to use anything but a fluorescent light due to limited space or heat problems in your grow room. In these cases Fluorescents can provide a viable way to grow where none existed before – although if you can manage it a small HID light will almost always perform better.

For more information about your lighting requirements or if you need any advice, please do not hesitate to call our technical team on 0845 345 5176.