Choosing lighting for growing Microgreens

Microgreens are an excellent source of vitamins, minerals and antioxidants, and they are easy to grow. However, the quality of Microgreens depends to a large extent on the type of lighting you use to grow them. In today’s article, we’ll explain how to choose an LED grow light for Microgreens and recommend some tried-and-tested options from our range.

A sufficient amount of light is essential for healthy plant growth and development. It drives photosynthesis, during which plants convert light into energy. While outdoors we can rely on sunlight, indoor growing often requires us to provide plants with supplementary lighting. This applies both to larger fruiting plants, such as tomatoes or chili peppers, and to Microgreens, which have slightly different lighting requirements from other plants.

This article deals only with lighting. For instructions on how to sow Microgreens, when to put them under lights, how to water them and when to harvest them, see our main guide How to grow Microgreens.

Microgreens go through several growth stages during their growing cycle, and their light requirements change accordingly. It all begins with the germination stage, when seeds absorb water and begin to grow. Seeds do not need light to germinate, but they do need a warm, moist environment. Once the seeds have germinated, Microgreens enter the growth stage, when they need bright light. The amount and intensity of light required vary, but in general, Microgreens need light in the PAR (photosynthetically active) spectrum, with wavelengths of 400–700 nanometres. After a few days to a few weeks, Microgreens are ready to harvest and no longer need light. They can be stored in the dark, where their growth will stop.

You might also be interested in: The light spectrum and its effect on plant growth: outdoors vs. greenhouse vs. indoors

Choosing suitable lighting for Microgreens

Unsuitable or insufficient lighting can easily thwart your plans for juicy, healthy sprouts. Insufficient light intensity will cause plants to develop elongated, thin stems and stunted leaves. An unsuitable light spectrum can result in distorted growth, yellowing leaves or even a poor taste in Microgreens.

Light spectrum

The light spectrum is the range of electromagnetic radiation visible to the human eye, and consists of light with different wavelengths. The visible spectrum consists of the colours seen in a rainbow: red, orange, yellow, green, blue, indigo and purple. Light with different wavelengths has different levels of energy: red light has a longer wavelength and lower energy, while purple light has a shorter wavelength and higher energy. In addition to visible light, there is also an invisible part of the spectrum, such as infrared radiation (with longer wavelengths) and ultraviolet radiation (with shorter wavelengths).

The spectrum emitted by modern grow lights generally corresponds approximately to PAR wavelengths, but the proportion of each colour in the spectrum will vary depending on the colour temperature, which is measured in kelvins (K). The “temperature” of the light emitted by a grow light indicates which types of plants and growth stages it is suitable for.

• 9000–11000 K (cool white) for germination and rooting cuttings.
• 5600–6500 K (blue) for growth and the vegetative stage.
• 2000-3000 K (red) for flowering, fruit production and ripening

The ideal spectrum for Microgreens is light with a predominance of blue, corresponding to 5600-6500 K, which supports rapid growth while also containing enough red light, which is important for young plants too.

Light intensity

Another metric that affects your choice of lighting for growing Microgreens is light intensity. The PPFD (photosynthetic photon flux density) value indicates how many photosynthetically active photons (in the PAR spectrum) reach the plants from the light. Together with the duration of lighting, intensity is a measurement that allows us to estimate how much energy the plants receive from light. The optimum light intensity for growing Microgreens is between 200 and 400 µmol/m²/s, with a recommended lighting duration of 12-16 hours per day.

In a study conducted by researchers at the University of Florida, Microgreens grown at low light intensity (around 50 µmol/m²/s) had lower yields and lower antioxidant activity than Microgreens grown at high light intensity (200 µmol/m²/s). At the same time, Microgreens grown under blue light had higher antioxidant activity than those grown under light with a predominance of red.

Higarden recommendations for Microgreens grow lights

GENT G-LED grow lights are energy-efficient LED lights specially designed for indoor growing of Microgreens. They offer a spectrum optimised for plant growth, particularly during the vegetative stage. GENT G-LED lights emit a white-blue spectrum with a colour temperature of 6500 K, making them ideal for growing Microgreens and other plants in the early stages of growth.

Would you like to learn more about indoor growing of Microgreens and other modern gardening techniques? Visit our Higarden blog!