I have grown microgreens under a kitchen window, under cheap fluorescent shop lights, and under full-spectrum LEDs. The difference in yield and quality is not subtle. Microgreens need 200 to 400 µmol/m²/s of photosynthetic photon flux density, 12 to 16 hours of light per day, and a light source positioned 6 to 12 inches above the tray. Get those three numbers right, and most lighting problems disappear.

Most home growers get into trouble with one of two mistakes: not enough light intensity or lights placed too far away. Both produce the same result: leggy, pale stems that stretch toward the source. I documented what proper versus improper lighting does to a crop in my book, Children of the Soil. The difference shows up fast, often within the first three days.

Blue light at 440 to 470nm drives leafy growth and chlorophyll production. Red light at 640 to 680nm matters more for flowering crops. Microgreens are harvested before they flower, so a blue-dominant spectrum is the priority. For indoor growers, a full-spectrum LED at 5000 to 6500 Kelvin covers both ranges without needing separate fixtures.

This post covers the science behind each lighting variable, how light affects nutrition and flavor, how to set up and monitor your grow lights, and what the latest LED technology offers for home and commercial operations.

What Light Do Microgreens Actually Need to Grow Well?

Microgreens are the children of the soil, between the infant sprouts and the young greens of all kinds of vegetables and herbs. They are on every main restaurant course it seems.

Only after the first true leaves are grown and packed with nutrients, which brings an explosion of flavour and color to various dishes, are microgreens harvested (see my post on how they grow, “The Easy Guide® To Growing Microgreens at Home”). However, it is crucial to understand their light requirements so that these miniature power plants can be successfully grown.

Light plays a pivotal role in the life of any plant, and microgreens are no exception. This is a significant driver of photosynthesis, the process whereby plants convert sunlight to chemical energy to fuel their growth. Without adequate light, photosynthesis is hindered, leading to leggy, pale, and underdeveloped microgreens. On the other hand, too much light can cause scorching and stunted growth. Striking the right balance is key.

The concept of using light to grow plants is not new. For centuries, farmers have relied on the sun to nourish their crops. However, artificial lighting has become increasingly popular with the advent of technology and the rise of indoor gardening. Today, various light sources, including fluorescent, LED, and even specialized grow lights, are used to grow microgreens indoors.

But it’s not just about turning on a light and letting it shine. The type of light, its intensity, its color spectrum, and the duration of exposure all influence how well your microgreens will grow. For instance, blue light promotes leafy growth, while red light encourages flowering and fruiting. For microgreens harvested before they flower, a light with a higher proportion of blue is often recommended.

The duration of light exposure, often referred to as the photoperiod, also matters. While mature plants often require periods of darkness to trigger certain growth stages, microgreens can generally tolerate more extended periods of light. However, they still need some darkness, as specific essential growth processes only occur during these ‘rest’ periods.

Understanding these principles and how to apply them to your microgreen cultivation can seem daunting, especially if you’re new to indoor gardening or farming. But don’t worry, we’re here to illuminate the subject.

In the following sections, we’ll delve into the specifics of microgreens lighting requirements, helping you optimize your setup for a bountiful harvest.

How Does the Light Spectrum Affect Microgreen Growth?

Light is a fundamental aspect of life on Earth. It fuels photosynthesis, the process by which plants, including microgreens, convert light energy into chemical energy to fuel their growth. Without adequate light, your microgreens will struggle to grow, leading to weak, leggy plants with poor nutritional content. But what exactly constitutes ‘adequate light’? Let’s delve into the science of light and its impact on microgreens.

Understanding the Light Spectrum

Light is not a single entity but a spectrum of different colors, each with its unique wavelength. These colors range from violet, the shortest wavelength, to red, the longest. Plants, including microgreens, respond differently to various colors of light. Blue light, for instance, promotes leafy growth, while red light encourages flowering and fruiting.

For microgreens, harvested before they flower, a light source rich in blue light is ideal.

The Role of Blue Light

Blue light, with a wavelength of approximately 400-500 nanometers, is particularly beneficial for leafy growth. This promotes the production of chlorophyll, which is a pigment that helps plants produce green color and plays an important role in photosynthesis. More chlorophyll means more energy production, leading to robust, healthy microgreens. Blue light also regulates plant growth by controlling the opening of stomata, tiny pores on the plant’s leaves that allow gas exchange.

Natural vs. Artificial Light

Microgreens can be grown under natural sunlight or artificial lights. While sunlight is the best light source for most plants, it’s only sometimes available, especially for indoor growers. Artificial lights, such as fluorescent lights or LEDs, can provide a consistent and controllable light source for your microgreens.

The Benefits of Artificial Light

Artificial lights offer several advantages for indoor growers. First, they provide a consistent light source, unaffected by weather or seasonal changes. Second, they allow for control over the light spectrum, intensity, and duration. This control enables growers to optimize the light conditions for their specific microgreens.

Choosing the Right Light for Your Microgreens

When selecting artificial lights for your microgreens, consider the light’s color spectrum, intensity, and duration. As mentioned earlier, microgreens prefer blue light, so look for lights with a high color temperature (5000 to 6500 Kelvin). The light intensity should be high enough to promote healthy growth but not so intense that it burns the plants. As for duration, microgreens generally need about 12 to 16 hours of light per day.

Positioning Your Lights

The distance between your lights and your microgreens is another crucial factor. If the lights are too far away, your microgreens may become leggy as they stretch toward the light. If the lights are too close, they could burn the plants.

A general rule of thumb is to keep the grow lights about 6-12 inches above your microgreens.

Monitoring and Adjusting Your Lighting

Once you’ve set up your lights, monitoring your microgreens and adjusting the lighting as needed is essential. If your microgreens are pale and leggy, they may need more light. If they show signs of burning, they may get too much light. Growing microgreens is a learning process; finding the perfect lighting conditions may take trial and error.

Light plays a pivotal role in the growth and development of plants, including microgreens. But it also significantly influences their nutritional content. Let’s take a look at light and its impact on microgreen nutrition.

How Does Light Change the Nutritional Content of Microgreens?

Light doesn’t just affect the growth of your microgreens; it also influences their nutritional content. Studies have shown that light’s type, intensity, and duration can affect microgreens’ concentration of vitamins, minerals, and antioxidants.[1][2] For example, red light has been found to increase the concentration of antioxidants in some microgreens, while blue light can enhance the levels of specific vitamins. By manipulating the light conditions, growers can potentially boost the nutritional value of their microgreens.

The process of photosynthesis, whereby plants can convert light energy into chemical energy, is well known. However, light does more than just fuel growth. Different wavelengths of light, represented in the light spectrum, can enhance or suppress the production of specific nutrients in plants.

Lighting for Different Microgreen Varieties

Different microgreen varieties may have slightly different light requirements. For instance, some microgreens may prefer a higher light intensity, while others may do better with less light. Some microgreens may also respond more positively to specific colors of light. It’s essential to research the specific light requirements of each microgreen variety you plan to grow.

Blue light, for instance, is crucial for promoting vegetative growth and the production of specific antioxidants. Microgreens exposed to a higher proportion of blue light tend to have higher levels of vitamins C, E, and K. They also show increased levels of carotenoids, which are beneficial for eye health.

On the other hand, red light stimulates the production of phenolic compounds, which have antioxidant properties and can protect the body against harmful free radicals. Red light also encourages the production of specific flavonoids, compounds known for their anti-inflammatory and immune-boosting properties.

Interestingly, the effects of light on microgreen nutrition aren’t limited to the growth phase. Post-harvest light exposure can also influence nutrient levels. For example, microgreens exposed to light after harvest can continue to produce nutrients, enhancing their nutritional value even further.

However, it’s important to note that manipulating light conditions can enhance certain nutrients and reduce others. Therefore, a balanced light spectrum ensures a well-rounded nutritional profile.

Light Intensity for Different Microgreen Varieties

In addition to the light spectrum, the intensity and duration of light exposure also play a role in nutrient production. Too little light can stunt growth and reduce nutrient levels, while too much light can cause stress and damage plants. Therefore, finding the right balance is key to optimizing microgreen nutrition.

Furthermore, the type of light source can also affect nutrient levels. While natural sunlight provides a full spectrum of light, artificial light sources such as LED lights can be tailored to provide specific wavelengths, allowing for more precise control over nutrient production.

Light plays a crucial role in determining their nutritional value by influencing the production of various nutrients. So, the next time you savor a handful of microgreens, remember you’re not just tasting the plant but also the light it has absorbed.

After exploring the intricate relationship between light and plant nutrition, let’s now look at how light affects the flavor and taste of microgreens.

 Does Light Affect the Flavor of Microgreens?

Light plays a crucial role in the development of microgreens, not just in terms of growth but also in influencing their taste and flavor. The type, intensity, and duration of light exposure can significantly affect the flavor profile of these tiny, nutrient-packed greens.

Blue light, in particular, has been found to enhance the flavor of microgreens. It promotes the production of plant compounds that contribute to taste. For instance, it can increase the concentration of glucosinolates in broccoli microgreens, giving them a more intense, spicy flavor.

Red light, on the other hand, can make microgreens taste sweeter. This is because red light stimulates the production of sugars in the plant, leading to a sweeter taste. For example, red light can enhance the sweetness of pea shoots and sunflower microgreens.

The duration of light exposure also matters. Longer light exposure can intensify the flavors of microgreens, while shorter exposure can result in milder flavors. However, it’s essential to strike a balance, as too much light can cause stress to the plants and negatively affect their flavor.

In addition to influencing taste, light can also affect the color and texture of microgreens. For example, microgreens grown under blue light often have a darker color and a more robust texture than those grown under red light. This is because blue light promotes the production of anthocyanins, plant pigments that give microgreens their vibrant colors.

By understanding the impact of light on microgreen flavor, color, texture, and nutrition, you can tailor your growing conditions to produce microgreens that suit your taste preferences and nutritional needs. You can take your indoor gardening to the next level by harnessing the power of microgreens lighting.

Explore microgreens taste and flavor in my post, “What Do Microgreens Taste Like?”

Now that we’ve explored the science of light and its impact on microgreens let’s discuss how you can apply this knowledge to your own microgreen cultivation.

How Do You Set Up Grow Lights for Microgreens Step by Step?

Whether you’re a home gardener, an urban dweller with a windowsill garden, a gourmet chef growing your own fresh garnishes, or an entrepreneur running a microgreen business, these practical tips and strategies will help you optimize your lighting conditions for robust, nutritious microgreens.

Choosing Your Light Source

The first step is to choose your light source. If you have access to plenty of natural sunlight, this can be an excellent light source for your microgreens. However, remember that the intensity and duration of sunlight can vary with the weather and seasons, and you may need to supplement with artificial light during darker months.

Artificial lights are the way to go if you’re growing microgreens indoors or in a location with limited sunlight. Fluorescent lights and LEDs are both excellent options for microgreens. They provide a consistent, controllable light source and can be adjusted to provide the optimal light spectrum, intensity, and duration for your microgreens.

Setting Up Your Lights

Once you’ve chosen your lights, the next step is to set them up correctly. The lights should be positioned about 6 to 12 inches above the microgreens. This distance provides intense light without the risk of burning the plants. As your microgreens grow, you may need to adjust the height of the lights to maintain this distance.

Monitoring and Adjusting Your Lighting Conditions

After setting up your lights, monitoring your microgreens and adjusting the lighting conditions is crucial. If your microgreens are pale and leggy, they may need more light. If they show signs of burning, they may get too much light. Growing microgreens is a learning process; finding the perfect lighting conditions may take trial and error.

Investing in a Light Meter

It may be worth investing in a light meter if you’re serious about growing microgreens. This device measures the light intensity in your growing area, helping you ensure your microgreens are getting the right amount of light.

For the latest in lighting innovations, explore my post, “247 Patents Certain to Influence Your Microgreens Business,” and explore more.

Understanding and optimizing the light conditions for your microgreens is not just a science – it’s an art. With the right knowledge, tools, and a bit of experimentation, you can master this art and grow microgreens that are not only robust and healthy but also packed with nutrition.

What Is the Latest in Microgreen Lighting Technology?

The future of microgreen lighting is bright, with advancements in lighting technology promising to revolutionize how we grow these nutritious greens. One such advancement is the development of tunable LED lights, which allow growers to adjust the light spectrum to match the specific needs of their microgreens. These lights can be tuned to emit more blue light for leafy growth or more red light for flowering, giving growers unprecedented control over their microgreens’ growth and development.[10]

Another promising development is using machine learning algorithms to optimize lighting conditions. These algorithms can analyze data from the growing environment, including light intensity, duration, and spectrum, and adjust the lighting conditions in real-time to maximize growth and nutrition. This technology could make it easier for growers to produce high-quality, nutritious microgreens.[11]

You can find more information in my post, “Harnessing Technology for a Greener Future: A Guide for Microgreens Entrepreneurs.”

Remember, having the right tools and knowledge is the key to successful microgreen gardening. With these products and services, you’ll be well on your way to growing your own fresh, nutritious microgreens.

Microgreens Lighting: Frequently Asked Questions

How far should grow lights be from microgreens?

Position grow lights 6 to 12 inches above the tray surface. Too far and seedlings stretch toward the light, producing weak, leggy stems. Too close and you risk light burn, particularly with high-intensity LEDs. As the tray grows taller, adjust the light height to maintain the same distance. A simple way to check: if your microgreens are pale and reaching upward, move the light closer by two inches and observe the next growth cycle.

How many hours of light do microgreens need per day?

Most varieties grow well with 12 to 16 hours of light and 8 to 12 hours of darkness per day. Darkness is not optional — specific metabolic processes only happen during rest periods. A programmable 24-hour timer takes the guesswork out of managing the photoperiod and prevents the common mistake of leaving lights running continuously. Continuous light does not accelerate growth and can stress the plants.

What type of grow light works best for microgreens?

Full-spectrum LEDs at 5000 to 6500 Kelvin are the most practical choice for home and small commercial growers. They run cool, consume less energy than fluorescent equivalents, and provide the blue-dominant spectrum microgreens need before harvest. Blue light at 440 to 470nm promotes chlorophyll production and leafy growth. Red light matters more for flowering crops — since microgreens are harvested at the cotyledon stage, blue-dominant spectrum is the priority.

Can you grow microgreens under regular household lights?

You can, but results will be inconsistent. Standard household bulbs lack the blue-spectrum intensity microgreens need for compact, nutritious growth. They work as a supplement to natural light but not as a primary source. If natural light is limited and you are relying on artificial sources, invest in a dedicated grow light rated at the correct color temperature and PPFD range. The cost difference between a basic grow light and a regular bulb is small relative to the improvement in yield.

Does light intensity affect the nutritional value of microgreens?

Yes. Research by Samuolienė et al. (2017) found that blue light exposure increases carotenoid and tocopherol levels in microgreens. Liu et al. (2022) confirmed that light intensity and photoperiod both affect vitamin concentrations in brassica microgreens. Blue light-grown microgreens show higher levels of vitamins C, E, and K. Post-harvest light exposure can also continue to influence nutrient levels after cutting.

What does PPFD mean and why does it matter for microgreens?

PPFD stands for photosynthetic photon flux density, measured in µmol/m²/s. It tells you how many light particles useful for photosynthesis are hitting the grow surface per second. For microgreens, the target range is 200 to 400 µmol/m²/s. Below that range, growth slows and stems get leggy. A basic light meter measures PPFD directly and removes the guesswork from light setup. For home growers, the ST6813 Portable Digital LCD Illuminance Meter covers the range needed.

Wrap-up: Microgreens Lighting Requirements

Understanding and optimizing the light conditions for your microgreens is crucial for their growth and nutrition.

In this comprehensive guide, we’ve shed light on the critical role lighting plays in microgreens cultivation.

We’ve discovered that while sunlight is the most natural plant light source, artificial lighting provides a controllable and consistent alternative, especially for indoor growers. Fluorescent lights and LEDs have emerged as the top choices for microgreen cultivation, offering the right balance of light spectrum, intensity, and duration.

But the importance of light in microgreen cultivation goes beyond just growth. The type, intensity, and duration of light can also influence the nutritional content of your microgreens, potentially boosting their levels of vitamins, minerals, and antioxidants. By manipulating the light conditions, you can grow healthier and more nutritious and flavorful microgreens.

As the popularity of microgreens continues to rise, so does the research into their optimal growing conditions. The future of microgreen lighting looks bright, with advancements in lighting technology and machine learning promising to revolutionize how we grow these nutritious greens. You can get the most out of your microgreens by staying informed about these advancements and incorporating them into your growing practices.

Remember, every great gardener was once a beginner who dared to sow that first seed. So, sow your seeds under the right light, and watch them grow into a lush, nutritious microgreen garden. Happy growing!

References

1. Samuolienė, G. et al. “THE IMPACT of SUPPLEMENTARY SHORT-TERM RED LED LIGHTING on the ANTIOXIDANT PROPERTIES of MICROGREENS.” Acta Horticulturae, no. 956, Oct. 2012, pp. 649–656, https://doi.org/10.17660/actahortic.2012.956.78. Accessed 13 Oct. 2021.
2. Liu, Kaizhe, et al. “Light Intensity and Photoperiod Affect Growth and Nutritional Quality of Brassica Microgreens.” Molecules, vol. 27, no. 3, 28 Jan. 2022, p. 883, https://doi.org/10.3390/molecules27030883. Accessed 10 Feb. 2022.
3. Samuolienė, Giedrė, et al. “Blue Light Dosage Affects Carotenoids and Tocopherols in Microgreens.” Food Chemistry, vol. 228, Aug. 2017, pp. 50–56, https://doi.org/10.1016/j.foodchem.2017.01.144. Accessed 7 Mar. 2021.
4. Kopsell, Dean A., et al. “Shoot Tissue Pigment Levels Increase in “Florida Broadleaf” Mustard (Brassica Juncea L.) Microgreens Following High Light Treatment.” Scientia Horticulturae, vol. 140, June 2012, pp. 96–99, https://doi.org/10.1016/j.scienta.2012.04.004. Accessed 24 Apr. 2022.
5. Zhang, Xiaoyan, et al. “Enhanced Anthocyanin Accumulation of Immature Radish Microgreens by Hydrogen-Rich Water under Short Wavelength Light.” Scientia Horticulturae, vol. 247, Mar. 2019, pp. 75–85, https://doi.org/10.1016/j.scienta.2018.11.060. Accessed 11 May 2023.
6. Xiao, Zhenlei, et al. “Assessment of Vitamin and Carotenoid Concentrations of Emerging Food Products: Edible Microgreens.” Journal of Agricultural and Food Chemistry, vol. 60, no. 31, 30 July 2012, pp. 7644–7651, pubs.acs.org/doi/abs/10.1021/jf300459b, https://doi.org/10.1021/jf300459b.
7. Brazaitytė, Aušra, et al. “The Effects of LED Illumination Spectra and Intensity on Carotenoid Content in Brassicaceae Microgreens.” Food Chemistry, vol. 173, Apr. 2015, pp. 600–606, https://doi.org/10.1016/j.foodchem.2014.10.077. Accessed 25 Mar. 2019.
8. Neo, Darren Chi Jin, et al. “Shaping and Tuning Lighting Conditions in Controlled Environment Agriculture: A Review.” ACS Agricultural Science & Technology, vol. 2, no. 1, 3 Jan. 2022, pp. 3–16, https://doi.org/10.1021/acsagscitech.1c00241.
9. Fylladitakis, Emmanouil D. “Controlled LED Lighting for Horticulture: A Review.” Open Journal of Applied Sciences, vol. 13, no. 02, 2023, pp. 175–188, https://doi.org/10.4236/ojapps.2023.132014. Accessed 9 Mar. 2023.
10. Zhu, Nanyang, et al. “Deep Learning for Smart Agriculture: Concepts, Tools, Applications, and Opportunities.” International Journal of Agricultural and Biological Engineering, vol. 11, no. 4, 8 Aug. 2018, pp. 32–44, https://doi.org/10.25165/ijabe.v11i4.4475. Accessed 16 Dec. 2020.
11. Altalak, Maha, et al. “Smart Agriculture Applications Using Deep Learning Technologies: A Survey.” Applied Sciences, vol. 12, no. 12, 10 June 2022, p. 5919, https://doi.org/10.3390/app12125919.
12. Bhaswant, Maharshi, et al. “Microgreens-A Comprehensive Review of Bioactive Molecules and Health Benefits.” Molecules (Basel, Switzerland), vol. 28, no. 2, 15 Jan. 2023, p. 867, pubmed.ncbi.nlm.nih.gov/36677933/, https://doi.org/10.3390/molecules28020867.
13. Report, Anne, and Hendriks. Producing a More Valuable Crop: Improving Nutritional Value, Shelf Life, Taste, and Appearance in Microgreens Using Pre-Harvest Light Treatments. 2021, studenttheses.uu.nl, https://studenttheses.uu.nl/bitstream/handle/20.500.12932/116/Research%20report%20final%20version%20pdf.pdf?sequence=1