" Blue light and the effect on plant growth | Herbal House NZ

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What is blue light and how does it affect plant growth

Whether you’re a new grower, or a seasoned hobbyist, you’ll likely already know that a major part of your plant’s growth potential is dependent on the light spectrum. And in this post,  we’re going to discuss the wavelength of blue light in particular. 

What is the wavelength of blue light? 

The wavelength of blue light is around 400-500nm and is a visible part of the light spectrum that has high energy and a profound effect on the flowering phase of the growth cycle.

As it is quite a short wavelength, the light can seem quite dim to the human eye. But for plants, it’s quite the opposite.

The effect of blue light on plants 

Blue photons (the cells your plant will receive from blue light) drives a photosynthetic reaction within the plant. For normal – or enhanced – plant growth, you should always be using a grow light that incorporates blue wavelengths.

What does stomata do in photosynthesis

Getting a little more technical, blue light helps to regulate the opening of stomata. Stomata are tiny doors on the leaves that allow the plant to remove excess water and take in carbon dioxide. Higher ratios of blue light can also help to improve plant quality through promoting root development and boosting nutrition.

It’s worth noting however, that high ratios of blue light can also reduce the PPFD of the crop, so it’s worth doing some intensive research into light recipes for your specific plant to ensure you don’t overdo it as too much blue light can cause harm to your plants.

Blue light vs red light plants 

Combining a mixture of both red and blue light for plants is always recommended. But how does blue and red light affect plant growth?

If plants are exposed to only red light, they will grow tall and have long branches with stretched out leaves. Although tall might sound great, the plants are usually pretty thin too.

For plants growing under mostly blue light, their growth can be suppressed. Plants will be shorter and have smaller leaves which are thick and dark. Neither scenario is particularly ideal. However, it’s helpful to understand the differences in order to manage how your plants grow.

Blue light is ideal for plants that are ornamental, as it can help to regulate growth and stop the plant from stretching out or growing too tall.

Putting red and blue together will help you to create tall, thick and leafy plants that are still healthy and strong.

Blue light is a supplementary wavelength and should not just be used on its own, combining this with red and green wavelengths will improve not only the health of your plants, but the rate at which they grow.