Best light spectrum for plants

Before you can choose a LED grow light, you need to know what the best light spectrum for plants is. On this page you will learn everything you need to know about it. 

A light spectrum is the range of wavelengths produced by a light source. These wavelengths are expressed in nanometers (nm) and correspond with a specific color. Plants use the photon energy that light provides for photosynthesis and photomorphogenesis, or growth and development. The frequencies of light that is most important to plants lies within the range of 400-700nm, also referred to as Photosynthetically Active Radiation (PAR). 

Horticraft Holland offers LED grow lights with different types of light spectra with the highest level of PAR output. Our lights are built with high-quality Samsung diodes that promise high PPF per Watt. Our spectra include a range of frequencies from Ultraviolet, Blue to Green, Yellow, and Red and even beyond, creating a light spectrum that mimics natural sunlight. Our light spectra are optimized to provide your plants with the energy they need to grow, providing you with higher yield and higher quality crops. Comparing the best light spectra with LED technology leads to less energy consumption and thus lower operating costs. 

So what is the best light spectrum for plants? Or better said, what is the best light spectrum for me? The best light spectrum for you should be the light spectrum that is used by the type of crop you are growing, but also depends on the light intensity of the grow light, the amount of actual light (PPFD) and other conditions.

Below you will find the best light spectrum for plants of different cultivations. Read carefully but if you have any question, please don’t hesitate to contact us.

The benefits of Full Spectrum LEd

 What makes full spectrum LED the best light spectrum for plants? Full Spectrum refers to light that covers all wavelengths from infrared to near-ultraviolet. All these different wavelengths have different benefits to plants. All wavelengths affect plants growth, disease control, quality, flowering, germination, and so on. These different wavelengths are The “Blue” wavelength (from 400-490nm) is primarily used during the plant’s vegetative growth phase, while “Red” wavelengths (580-700nm) are used during flowering and fruiting.

More Photons

The number of photons (light energy) supplied by Full Spectrum LED grow lights far outnumber the number of photons from non-Full-Spectrum light sources. This means that Full Spectrum LED grow lights provide plants with more energy to grow and consequently more yield for the grower. 

Better PAR Value

While HPS and HID grow lights put out a high PAR value, a lot of this value comes from high spikes in one or two colors, and this may actually be harmful to your plants since they need a spectrum that closely resembles that of the light that the plant’s chlorophyll maximally absorb. Full Spectrum LED grow lights pump out a better (optimized) PAR value.

Healthier Plants

While it is true that Blue and Red wavelengths are the most effective, your plants need frequencies from the entire light spectrum at any stage of their growth. Providing your plants with Blue light only during the vegetative phase will not give you the best results. Plants that are given wavelengths from across the entire spectrum are generally healthier. 

Spotting Sick Crops

Using a Red and Blue combination (“Blurple”) light will make it difficult to see your crops clearly, which will also make it difficult to check your crops for diseases, pests, and fungi. Growers using full-spectrum light see their crops in natural light and can easily check up on growth and intervene when things go wrong. 

Mimic Sunlight

Plants have used sunlight to grow and evolve for millions of years, so we could say that grow lights that mimic sunlight may be most beneficial to plants. While it is true that the Red and Blue wavelengths provide the most energy for photosynthesis (growth), they will grow faster, stronger and healthier when you use the full light spectrum, including Green, Yellow, Ultraviolet and Far-Red. 

Added Benefits

Different plants respond to different wavelengths in various ways. While a Red and Blue spectrum will benefit photosynthesis, adding extra wavelengths outside of these two can actually help stem growth or increase flowering, or even make your plants flower earlier compared to using only Red and Blue. Different wavelengths promote certain plant morphology during different stages of growth

Benefits of specific wavelengths - dissecting the best light spectrum for plants

Ultraviolet (100-400nm)

Ultraviolet (UV) light lies between 280-400 nm and is harmful to all living beings, including plants. Exposing your plants to too much UV isn’t a good idea, however you can utilize your plant’s defense mechanisms to enhance them. To protect itself, a plant will initiate physical and chemical defense mechanisms and produce antioxidants to protect itself.. These compounds make your plant more colorful, and make them smell and taste better. 

What’s more, these defense mechanisms do not just protect our plants from UV damage, but can also make them more resistant against stress, pests, and fungi (Suthaparan, 2016). Read more about Ultraviolet…

Blue (440-490nm)

Blue light lies within the 440-470nm range. These light wavelengths  encourage seedling and vegetative leaf growth. Blue light produces more lush plants that have stronger stems and stronger root growth. Blue light helps to create the chlorophyll necessary for plant processes and increases the production of secondary metabolites that protect your plant against pests and herbivores. Blue wavelengths help control a plant’s respiration and thereby lessening water loss through evaporation. 

Green (490-560nm)

Chlorophyll do not absorb Green light as well as Blue or Red light. Plants generally reflect 10-50% of the Green wavelengths, making them appear green to the human eye. However, this does not mean that Green light is not important. Green light is great at penetrating through the canopy and can therefore provide the lower parts of your plant with energy. This leads to losing less lower leaves. 

Furthermore, when chlorophyll molecules reach a saturation point and can no longer absorb Red and Blue wavelengths, Green light can excite the electrons within the chlorophyll, enhancing photosynthesis and leading to increased crop yields (Kaiser, 2019). Green light also plays a role in regulating the opening and closing of the stomata (tiny openings in the leaves that allow for gas exchange) and help in the production of chlorophyll.

Yellow & Orange (560-625)

Yellow and Orange wavelengths have the lowest effect on plants, but can still be beneficial. These wavelengths increase photosynthesis, flowering, and growth. Yellow and Orange also affect your plant’s leaves growth, and can result in greater yield and higher quality crops. Yellow and Orange light do not affect chlorophyll production, but have been found to affect phycocyanin receptors.

Red (625-710nm)

Red wavelengths help plants during the flowering phase. These wavelengths encourage stem growth, flowering and fruit production, chlorophyll production, while increasing photosynthesis, leaf count, and yield. 

Plants associate Red light with a being in the shadow or a setting sun and it has therefore an effect on your plant’s resting periods. Providing your plants with too much Red light may make them think they are in the shade all the time and will make them stretch and grow tall (with thin leaves) to get themselves out of this shady spot. For this reason, it is important to not rely on one wavelength but always use a combination of different wavelengths of light to influence the plant’s development and grow healthy plants.

Far-Red (710-780)

This wavelength is associated with germination, flowering, leaf size, plant elongation and resting. Plants interpret high amounts of Far-Red as being in the shadows. The ratio of Red to Far-Red light (R:FR) influences phytochromes, a class of photoreceptors. These can reduce the time a plant takes to fall asleep, thereby reducing the overall resting time a plant needs. This leaves more time in the light, and thus for growth, resulting in a greater yield. 

Far-Red may also reduce the time a plant needs to flower, resulting in earlier harvests. Just like Green frequencies, Far-Red light can penetrate deeper into the canopy, providing energy to lower leaves. Read more about Far-Red…

Kaiser, E. et al. (2019). Partial replacement of red and blue by green light increases biomass and yield in tomato. Scientia Horticulturae 249, 271-279.

Heuvelink, E. (2020). White light boosts tomato and cucumber yields. Working under white light is much more pleasant. In Greenhouses 9, 10-11.

Suthaparan, A. et al. (2016). Suppression of Powdery Mildews by UV-B: Application Frequency and Timing, Dose, Reflectance, and Automation. Plant Dis. 100, 1643–1650.

Kalaitzoglou, P., van Ieperen, W., Harbinson, J., van der Meer, M., Martinakos, S., Weerheim, K., Nicole, C., & Marcelis, L. (2019). Effects of Continuous or End-of-Day Far-Red Light on Tomato Plant Growth, Morphology, Light Absorption, and Fruit Production. Frontiers in plant science, 10, 322.

 

 

Chart of the effects of different wavelengths on plant growth. Dissecting the best light spectrum for plants