Microgreen Fact Sheets, Urban Farming

Maximizing Microgreen Growth: The Value of LED Grow Lights for Indoor Cultivation

led grow lights

Introduction

Indoor gardening has become increasingly popular, particularly for cultivating microgreens, due to the convenience and control it offers. One crucial factor in successful indoor microgreen cultivation is lighting. In recent years, LED (Light Emitting Diode) grow lights have emerged as a highly efficient and effective lighting option for indoor gardening. This article explores the value of using LED grow lights for indoor growing of microgreens, backed by studies comparing the use of lights versus natural light, and provides insights into the ideal light levels for optimal growth.

Advantages of LED Grow Lights

  1. Enhanced Photosynthesis: LED grow lights provide specific light wavelengths that closely match the photosynthetic spectrum, promoting efficient photosynthesis in plants. Unlike traditional lighting sources, LEDs emit light in narrow bands, allowing growers to customize the light spectrum based on the specific growth stage of microgreens.
  2. Energy Efficiency: LED grow lights are known for their remarkable energy efficiency. They produce more light per watt compared to traditional lighting systems, resulting in reduced energy consumption and lower electricity costs. This efficiency enables growers to sustain longer light cycles without excessive energy consumption, supporting optimal growth.
  3. Heat Management: LED grow lights produce minimal heat compared to conventional lighting options. This allows growers to position the lights closer to the plants without the risk of heat damage, ensuring consistent light distribution and minimizing energy wastage.

Studies Comparing Lighting Methods

Several studies have compared the use of LED grow lights with natural light or other artificial lighting methods for microgreen cultivation:

  1. A study published in the journal HortScience (Barnes et al., 2016) compared the growth of microgreens under natural sunlight, fluorescent lights, and LED grow lights. The results demonstrated that microgreens grown under LED lights exhibited higher biomass, increased nutrient content, and improved color intensity compared to those grown under other light sources.
  2. Another study published in the journal PLOS ONE (Bantis et al., 2018) compared the growth of basil microgreens under different lighting conditions, including LEDs and high-pressure sodium (HPS) lights. The findings indicated that microgreens grown under LED lights exhibited superior growth rates, increased biomass, and higher concentrations of health-promoting compounds.

Ideal Light Levels for Microgreens

The ideal light levels for microgreen cultivation can vary based on the specific plant variety and growth stage. However, as a general guideline, microgreens typically require a light intensity of around 200 to 400 μmol/m²/s (micromoles per square meter per second) during the germination and growth stages. During the later stages, light levels can be increased to approximately 300 to 600 μmol/m²/s to promote optimal growth and development.

How many hours a day should plants get light?

The duration of LED lights being on in a 24-hour period for microgreen cultivation depends on the growth stage of the plants. Generally, microgreens require a balance between light and darkness to mimic natural day-night cycles and ensure healthy growth. Here are some guidelines for the duration of LED light exposure:

  1. Germination Stage: During the initial germination stage, microgreens benefit from continuous darkness for proper sprouting. Keep the LED lights off or provide minimal lighting for around 48 to 72 hours until the seeds have sprouted and the cotyledons (seed leaves) are visible.
  2. Growth Stage: Once the microgreens have sprouted, you can introduce light to promote growth. The recommended light cycle for the growth stage is typically around 12 to 16 hours of light exposure per day.
  3. Rest/Dark Period: Microgreens, like most plants, require a period of darkness for physiological processes such as respiration and recovery. Provide a rest period of 8 to 12 hours of darkness during the remaining 24-hour period. This allows the plants to rejuvenate and prevents potential issues like overexposure or stress.

It’s important to note that different microgreen varieties may have specific light requirements. Some may thrive with slightly longer or shorter light exposure, depending on their growth characteristics. Monitoring the growth and response of your specific microgreens is key to fine-tuning the light cycle for optimal results.

Additionally, it’s advisable to use a timer to automate the light cycle and maintain consistency. This ensures that the microgreens receive the appropriate amount of light and darkness consistently, promoting healthy growth and development.

Remember, while providing sufficient light is essential, avoiding excessive exposure or extended light periods is equally important. Always refer to the specific guidelines for the microgreen varieties you are cultivating and adjust the light cycle accordingly for the best results.

The difference between Lumens and PPFD

Lumens and PPFD (Photosynthetic Photon Flux Density) are two different ways to measure light, and they serve distinct purposes when it comes to understanding the characteristics of light for plant growth. Here’s a breakdown of each measurement:

Lumens: Lumens are a unit of measurement that quantifies the total amount of visible light emitted by a light source as perceived by the human eye. It is a measure of light intensity weighted according to the sensitivity of human vision. Lumens are commonly used to measure light output for general lighting applications, such as in homes, offices, or outdoor areas. However, when it comes to assessing light for plant growth, lumens have limitations.

Plants do not respond to all wavelengths of visible light in the same way as the human eye does. They have specific light absorption peaks in the blue (400-500nm) and red (600-700nm) regions of the spectrum, which are crucial for photosynthesis and growth. Lumens do not consider these specific wavelengths and, therefore, may not accurately reflect the effectiveness of light for plant growth.

PPFD (Photosynthetic Photon Flux Density): PPFD measures the quantity of photosynthetically active photons (light in the 400-700nm range) that reach a specific area per unit of time. It quantifies the light intensity relevant to photosynthesis and plant growth. PPFD is expressed in micromoles per square meter per second (µmol/m²/s). This measurement provides a more accurate representation of the light available for plant photosynthesis.

PPFD takes into account the distribution of light across the spectrum and its relevance to plant physiology. It considers the light energy that plants can absorb and convert into chemical energy through photosynthesis. PPFD values help growers understand the intensity and quality of light in a given area, enabling them to optimize light distribution and determine the ideal light levels for specific plants or growth stages.

When evaluating light sources for indoor growing, such as LED grow lights, PPFD is a crucial metric to consider. It helps determine if the light source can provide sufficient photosynthetically active light for healthy plant growth.

In summary, lumens measure the total visible light output as perceived by the human eye, while PPFD quantifies the specific light energy available for photosynthesis. For accurate assessment of light suitability for plant growth, PPFD is the preferred measurement as it focuses on the light wavelengths relevant to plants and their photosynthetic processes.

Conclusion

LED grow lights have revolutionized indoor gardening by offering numerous advantages for cultivating microgreens. They provide tailored light spectra, promote energy efficiency, and allow precise control over light cycles. Studies comparing LED grow lights with natural light or other lighting methods consistently demonstrate the superior growth, increased biomass, and nutrient content of microgreens grown under LEDs. For indoor growers seeking optimal yields and excellent microgreen quality, investing in LED grow lights is a worthwhile endeavour.