LED Grow Light Optimization: Here’s the Solution

Are you struggling to harness the full potential of your LED lighting setup? Perhaps your plants appear somewhat leggy, or your electricity bills are unexpectedly high. While LED grow lights offer customizable light spectrums and intensities—enabling ideal conditions for plant growth—your plants may not be flourishing as anticipated.

The challenge lies in the fact that there is no consensus on LED configuration for the growth of any particular plant species. Moreover, the efficiency of lighting is also influenced by the growing environment. This lack of clarity can leave growers perplexed about how to optimally utilize their LED grow lights, complicating the process of optimization. To solve the problem, multiple experiments and research have been implemented for the optimization of LED grow lights for different plants.

In this blog, we will discuss some main factors and experiments for LED grow light optimization.

Light spectrum

Some light wavelengths have been proved to be effective in promoting plant growth and development. Red and blue light is generally recognized as the most important lights in the PAR range for photosynthesis. Red light stimulates biomass accumulation and flowering. Blue light promotes stoma opening/closing regulation mechanism, chlorophyll, and plant morphology. Green light regulates leaf expansion and stem stretching.

However, the effects of light spectrum on plants are complex. Different ratios of wavelengths can have huge different impact on plant growth and yields. A study by Filatov and Olonin investigated the optimal lighting conditions to maximize microgreen yields while minimizing energy usage and electricity costs. The researches conducted experiments testing different ratios of blue, red, and far-red LED lights on cabbage and radish microgreens. They found that the fresh and dry weights of microgreens were greater at 75% red light than at 50% and 25%. But there was little effect on increasing yields when red light about 70% regardless of microgreen variety. This showed that increasing the proportion of red light significantly increased fresh and dry weight yields for both varieties. They also found that the optimal lighting strategy was 29% blue: 58% red: 13% far-red LEDs.

Another research from the Russian Lighting Research Institute provided some insights by testing different LED light recipes on lettuce and basil plants. Across experiments, the researchers found red light (660nm) consistently produced the highest yields of fresh biomass for both lettuce and basil. While blue light (447nm) outperformed green light (518nm) for promoting lettuce growth, greenhouse light wasn’t as ineffective as assumed. At 100 μmol/m²/s, green light allowed higher productivity than both blue and red light for lettuce.

Light intensity

Light intensity refers to the amount of light that plants receive within a specific area over a given period. Similar to the light spectrum, light intensity also directly influences photosynthesis. Photosynthetic photon flux density (PPFD) is used to measure the light intensity. Existing literature often adopts light intensities from 100 to 300 μmol/m²/s.

A study conducted by researches at the University of Bologna, in collaboration with Wageningen University and Research, aimed to define the optimal PPFD for indoor cultivation of lettuce and basil under red and blue LEDs. The study found that a PPFD of 250 μmol/m²/s (Daily Light Integral of 14.4 mol/m²/d) resulted in improved fresh and dry biomass productions, as well as larger plant leaf area, compared to lower or higher light intensities. Furthermore, this light intensity led to increased antioxidant capacity, phenolics, and flavonoid concentrations in lettuce, enhancing its nutritional quality.  

Light distribution

Optimizing the distribution of LED grow lights is a critical aspect of indoor agriculture, directly influencing crop quality and yield. Uniform lighting is paramount to ensure consistent growth across all plants. However, achieving this uniformity involves careful consideration of optical design and strategic placement.

Excessive light intensity can create hot spots. This can lead to uneven growth, with plants directly under the lights flourishing at the expense of those in shadowed areas. Moreover, taller plants may cast shadows on smaller ones, exacerbating the imbalance. To mitigate these issues, interlighting is a promising technique, particularly beneficial for vine crops. By strategically placing lights within the canopy, interlighting ensures a more even distribution of light from the top to the lower sections of plants.

Beyond just placement, the distance and height between lights and plants play a crucial role in optimizing growth. During the vegetative stage, lights should be positioned closer to encourage robust growth. However, as plants transition to the flowering stage, greater distance is necessary to prevent heat damage and optimize flowering. 

Additionally, the wattage of the grow lights influences their placement. Higher-wattage lights should be positioned further away to prevent burning, while lower-wattage lights can be placed closer for optimal coverage.

Light control

Unlike the unpredictable nature of sunlight, LEDs provide consistent and customizable light spectrums and intensity levels. Dimmable LED grow lights offer a nuanced approach to lighting, allowing for tailored illumination suited to varying plant needs. By adjusting the intensity of light, growers can promote even growth throughout their crops. Additionally, dimmers and timers enable the replication of natural sunrise and sunset transitions, fostering optimal conditions for plant health and growth cycles. Furthermore, LEDs offer specific light intensities tailored to different stages of plant development, resulting in increased energy efficiency and reduced carbon emissions, contributing to a more sustainable cultivation process.

Environmental control

Environmental control is a crucial aspect of optimizing the effects of grow lights on plant growth. While factors like humidity, water, and temperature are well-known, some lesser-known elements can significantly impact plant health and yield. One such factor is the distinction between ambient room temperature and leaf surface temperature. Photosynthesis, the process that drives plant growth, occurs within the leaves themselves. Therefore, measuring the ambient air temperature alone is insufficient for an indoor grow facility.

Take the cultivation of cannabis as an example. Most temperatures of the cannabis plant are between 22°C and 30°C, typically higher than the surrounding air. LED grow lights, while energy-efficient, still generate heat during operation, which can potentially burn plants. However, optimized lighting systems can produce more usable light for photosynthesis, allowing plants to convert that energy into chemical energy rather than heat, resulting in lower leaf temperatures. By maintaining appropriate leaf temperatures, plants can achieve higher rates of photosynthesis and, consequently, better growth.

Another often overlooked factor is the concentration of carbon dioxide (CO2) in the growing environment. With ambient CO2 levels around 300 ppm and temperatures ranging from 5°C to 27°C, the rate at which plants absorb and convert CO2 into sucrose increases with rising temperatures, leading to increased net photosynthesis.