What colours should an LED grow light have?

colours that plants require for photosynthesis

What colours should an LED grow light have?

It can be pretty confusing when you first look at buying LED grow lights because there are so many shapes and sizes with different combinations of colours and intensities. Some people who have bought cheap, imported LED grow lights have seen poor results which has jaded their opinion of LED grow lights. Other people, who have bought higher quality LED grow lights have seen much more positive results.

To start analysing the best type of LED grow lights on the market, we should first start with the goal in mind and examine what it is that plants are actually looking for.

What light waves do plants prefer?

Sunlight growing plants

Plants need sunlight to grow

Sunlight, which is key to a plants survival, consists of light which contains a rainbow of different colours. These different colours are called wavelengths. Plants will use this light to grow and survive. Plants will use more of one colour light than the other. By understanding which wavelengths plants will use at which stage of their development will help you grow healthier plants with a bigger yield of fruit / flowers.

The right light spectrum, light intensity and light duration all work together to trigger plant flowering, growth and reproduction.

You can actually start to trick plants into growing into various stages by using LED grow lights and the different types of wavelength colours that you focus on.

colours that plants require for photosynthesis

Plants use lots of blue / red light

The light which we can see (called the visible light spectrum) emits light in red, orange, yellow, green, blue, indigo and violet colours. It is the colours on either end of this spectrum which play the greatest role in plant growth and flowering, while the colours in the middle (yellow and green) wavelengths play a lesser role.

Sunlight is a great light source for plants and naturally provides all of these wavelengths. Plants have evolved over years to use this light. Different wavelengths are used for specific plant functions, but all colour wavelengths in this range are absorbed in varying amounts. Wavelengths in the red and blue spectrum are absorbed in greater amounts while more green and yellow light is reflected, giving the leaves their characteristic green colour.

It is for this reason that LED grow lights have a greater emphasis on the blue and red parts of the spectrum. It is these colours that help plants grow best.

Colour spectrum for plant growth

Plants require different colours at different stages of growth. Blue for early vegetative (growth) stages and red for later (flowering) stages.

The importance of blue light on plant growth

The most important blue wavelengths are from 430 to 450 nm (nanometers). This is known as cool light. In nature, there is lots of blue light in the spring time so when the plant detects blue light, it encourages vegetative growth through strong root growth and intense photosynthesis.

Blue light is often used alone with LED grow lights during the early phases of plant growth, such as starting seedlings, when flowering is not desired.

The importance of red light on plant growth

The longer wavelengths of light are red in colour. They travel further than many other wavelengths. The is known as warm light. In nature, there is lots of red light in the end of summer/autumn time so when the plant detects red light, it encourages stem growth, flowering and fruit production.

Red light is often used alone with LED grow lights during the late phases of plant growth, such as flowering and yielding the plants crops. LED grow lights that emit red light are normally used right at the end of the plant growth phase.

The importance of green and yellow light on plant growth

The middle part of the wavelengths are generally green and yellow light. Not all light emitted by nature or an LED grow light is absorbed. Most green light is reflected which gives plant leaves their green colour. Most of the colours absorbed and used by the plant from nature or LED grow lights are blue and red. That said, it is important to have some green

Light intensity on plant growth

Flowers require sunlight

PLants require sunlight to photosynthesis

Different plants require different levels of light intensity. In nature, some plants thrive in direct sunlight whereas others thrive in shade. The level of light intensity is completely dependant upon the type of plant you are growing.

LED grow lights / lamps can replicate light intensity of the sun by placing further away or closer to the plant. Because LED grow lights do not get hot, unlike conventional grow lights, there is no danger of damage to the plants.

Light duration on plant growth

The amount of light that your plant receives everyday is important, especially when it comes to the flowering / fruiting period. For indoor plant growth under LED grow lights, a minimum 12 to 14 hours of light per day is usually needed. This is where LED grow lights come into their own. They do not get hot and use much less energy than conventional grow lights.

Again, if you are growing plants which tend to grow over a period of months and you want to increase your yield, you can adapt your light duration by replicating light exposure in nature. To replicate shorter days in the spring, you use less LED light and slowly increase it to replicate the longer days of summer before again reducing the light exposure to replicate the shorter days of autumn/fall.

LED grow lights offers everything

LED grow lights are the future of horticulture. They are cheap to run and offer massive benefits. You can grow a plant / crop in the fraction of the time and even help manipulate the beneficial growth of that plant using science. Although grow lights have been around for a number of years now, the market for LED grow lights is growing massively. It is safe to say, the future is here now.

How to choose the best LED grow lights

About the Author

I first got into LED grow lights when a close friend started suffering from multiple sclerosis and needed medicinal solutions to help manage their condition.

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