Lighting for microgreens is one of the most misunderstood parts of microgreen growing, and it’s also one of the easiest places to overspend, overcomplicate, or get distracted by numbers that don’t actually improve results. We’ve written this guide to clear the air. The aim isn’t to turn you into a lighting engineer, but to help you make informed decisions about what is often the single biggest equipment expense in a microgreens setup.
For microgreens, lighting is not about maximising yield at all costs. It’s about consistent colour, predictable growth speed, and repeatable results across shelves, while keeping heat, electricity use, and labour under control. If your lighting helps you harvest on time, week after week, without fighting the environment, it’s doing its job.
What light actually does in microgreens production
It helps to start by understanding what light is actually doing for microgreens. These crops are harvested very young. They don’t need the intense light levels required by fruiting crops, full-size leafy greens, or long-cycle herbs.
For microgreens, light mainly influences:
- Leaf colour and chlorophyll development
- Stem thickness and strength
- Growth speed and harvest timing
- Post-harvest appearance and shelf life
Once a minimum threshold is reached, adding more light brings diminishing returns. In some cases, it actively works against you by increasing heat load, water demand, stress, or drying.
More light is rarely the goal. Even, sufficient light is.
Types of lighting used for microgreens
Sunlight
Sunlight is excellent in theory, but inconsistent in practice. Indoors, it’s hard to rely on due to seasonal variation, low winter light levels, and uneven distribution across racks. Sunlight works best in greenhouses, mixed systems with supplemental LEDs, or non-commercial and seasonal setups.
Fluorescent lighting
Fluorescent lighting was once the standard for microgreens and still produces acceptable results, but it’s largely outdated. Lower energy efficiency, shorter lifespan, bulkier fixtures, and dwindling replacement availability mean it’s rarely the best choice for new systems.
LED grow lights for microgreens
LEDs have become the default for good reason. They offer high efficiency, low heat output, long lifespan, compact form factors, and predictable performance. For rack-based growing, LED bars or tubes are particularly practical because they distribute light evenly across trays and integrate cleanly into shelving systems.
For most commercial growers, microgreens LED lighting is the clear long-term choice.
Understanding PPFD and light intensity for microgreens
Where many growers get stuck is in the specifications. Lighting listings are full of numbers, and most of them are either confusing or irrelevant.
PAR describes the range of light plants can use. Almost all grow lights produce PAR, so this number alone doesn’t tell you much.
PPF tells you how much usable light a fixture emits in total, but not how that light is distributed.
PPFD is the number that actually matters. PPFD tells you how much usable light reaches the crop surface. Plants respond to light at the leaf, not at the fixture. PPFD accounts for distance and spread, which makes it the most meaningful metric for growers.
When possible, think in terms of PPFD at canopy height, not wattage or marketing claims.
How much light do microgreens need?
Across research trials and commercial practice, most microgreens perform well within a relatively low to moderate range.
100–200 µmol·m⁻²·s⁻¹ PPFD is a reliable starting point for most systems.
- Below 100: crops may stretch or colour poorly
- Above 200: gains are often marginal and increase heat or stress
Different crops respond differently, but this range keeps things predictable without pushing the system.
Light distance and uniformity
Distance from the canopy matters just as much as light output. Small height changes can cause large swings in PPFD.
For LED bars over racks, lights are commonly mounted 20–40 cm above the crop. Uniformity matters more than peak intensity.
It’s almost always better to run slightly lower intensity evenly than high intensity unevenly.
Photoperiod for microgreens
Most growers run lights between 12 and 18 hours per day. Shorter photoperiods can work perfectly well if production schedules are adjusted.
Longer days allow lower intensity to achieve the same total daily light, while shorter days require higher intensity to maintain growth speed.
Moderate intensity paired with a moderate photoperiod tends to give the most consistent commercial results.
Spectrum and colour temperature
Most modern “grow” LEDs are white LEDs with a balanced spectrum. For microgreens, white LEDs work extremely well.
Colour temperature (Kelvin) describes how warm or cool light looks. Mid to cool white performs reliably.
CRI affects how colours appear to humans, not how plants grow. It matters for presentation and photography, not yield.
“Full spectrum” is largely marketing language. Focus on PPFD and uniformity instead.
Electricity cost and scaling lighting systems
Electricity cost is often misunderstood. A simple calculation keeps it grounded.
If a light draws 40 watts and runs 16 hours per day, that’s 0.64 kWh daily. At £0.30 per kWh, that’s about 19 pence per day — roughly £5.70 per month per light.
Multiply by the number of fixtures and you have a realistic monthly operating figure. This clarity makes scaling decisions rational rather than emotional.
Troubleshooting lighting issues
- Stretching: light too weak or too far
- Pale colour: insufficient PPFD or photoperiod
- Uneven growth: poor distribution
- Leaf bleaching: excessive intensity too close
- Algae: stray light hitting water surfaces
Change one variable at a time so you can see what actually helped.
The commercial mindset
Lighting for microgreens is about consistency, not intensity. Once you meet the crop’s basic needs, your job is to make that light even, repeatable, and affordable to run.
If your lighting helps you hit harvest days reliably without adding heat, stress, or unnecessary cost, it’s doing exactly what it should.
FAQ
What is the best PPFD for microgreens?
Most perform well between 100–200 µmol·m⁻²·s⁻¹ at canopy height.
How many hours of light do microgreens need?
Typically 12–18 hours, depending on intensity and production timing.
Are red and blue grow lights necessary?
No. White LED lighting works extremely well for most microgreens.
References
- Kyriacou, M. C. et al. (2019). Microgreens as a component of space life support systems: A review. Frontiers in Plant Science.
- Samuolienė, G. et al. (2012). The impact of LED illumination on antioxidant properties of microgreens. Journal of Agricultural and Food Chemistry.
- Pennisi, G. et al. (2020). Optimal light intensity for indoor cultivation of microgreens. Scientia Horticulturae.
- U.S. Department of Agriculture (USDA). Light and plant growth fundamentals.
- University extension publications on controlled environment agriculture and microgreen production.
- Commercial microgreen production manuals (UK, EU, USA).