One of the most common questions new microgreen growers ask is: "Do I need special grow lights to grow microgreens, or will my windowsill work?" The simple answer is that while microgreens do need plenty of light to grow healthy, you don't necessarily need expensive specialty grow lamps. Many home growers successfully use sunlight or basic indoor lights. However, understanding microgreens' light requirements will help you choose the best setup for consistent, robust growth. This beginner's lighting guide will explain how much light microgreens need, what types of lights work, and how to use lighting to avoid leggy or weak sprouts.
By the end, you'll know how to provide optimal lighting for your microgreen garden - whether it's by a sunny window or under LED lamps - and we'll clear up the "special grow light" myth.
Natural Light vs. Artificial Light
Natural Sunlight: If you have a bright window or sunroom, congratulations - you have a free grow light! Microgreens can be grown under natural daylight, especially from late spring to early autumn when days are long. A south-facing window that gets a few hours of direct sun is often sufficient. For instance, many people can grow microgreens on a kitchen windowsill that receives ~4+ hours of direct sun and bright indirect light the rest of the day. Sunlight provides the full spectrum of light (all colors) and is intense enough to produce sturdy, flavorful microgreens.
However, there are some considerations with window growing. First, light from a window is directional - microgreens will tend to bend toward it, resulting in a slight lean or "leggy" growth if not enough intensity. You can counteract this by rotating your trays daily. Second, windowsill light is weaker in winter or in consistently overcast weather. Microgreens grown in insufficient light may become pale (yellowish) and thin as they stretch for more light. If you notice your microgreens growing very tall with small leaves and a yellow tint, it's a sign they aren't getting enough light. Lastly, near a window the temperature can fluctuate (chilly nights, hot midday sun behind glass). Most microgreens prefer stable room temperatures, so you may need to move trays a bit if they get too cold or hot in the window.
Despite these nuances, many beginners start with sunlight and do just fine. Pros: It's free and full-spectrum, no setup needed. Cons: It's variable (seasonal, weather-dependent) and sometimes not strong enough in winter, leading to slower growth. Also, if you want to grow more than a tray or two, windowsill space can be a limiting factor.
Artificial Light: Using artificial lighting gives you more control and consistency. But do you need a "special" grow light? - Not necessarily. Microgreens have a short growth cycle and don't require the intensity or particular color spectrum that fruiting plants (like tomatoes or orchids) might need. In fact, a variety of light sources can work:
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LED or Fluorescent Shop Lights: A basic LED shop light (the kind used in garages, typically 4-foot/120 cm tubes) or a fluorescent fixture (T5/T8 tubes) can grow microgreens well. Aim for cool white or daylight spectrum (around 5000K-6500K color temperature). This is because that range mimics natural daylight and has a good balance of blue and red light for vegetative growth. Many growers have found that inexpensive LED bulbs or tubes labeled "daylight" do just as fine a job as costly plant-specific lights. Ensure the fixture is placed close enough (more on distance in a moment). Modern LED shop lights are preferred over old fluorescents because LEDs use less power, run cooler, and last longer. If you only have fluorescent lights, they can still work - just be mindful of heat and replace bulbs as they dim over time.
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Dedicated Grow Lights: These include LED grow panels, high-output T5 fluorescent grow lights, etc. They often advertise specific spectral outputs (lots of blue and red for plant growth). These are effective, but often their advantage is more crucial for long-term or fruiting plants. Microgreens will be perfectly happy under full-spectrum white light. That said, if you plan to stack shelves of microgreens, investing in slim LED grow lights that can daisy-chain (connect in series) might be worthwhile for convenience. For example, there are T5 LED bar lights that can link 6-8 bars on one plug, which is neat for multi-tier setups. If you already own a grow light, by all means use it. Just know it's not an absolute requirement.
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Household Lamps and Bulbs: In a pinch, you can use a strong desktop lamp or clamp light with a cool-white LED or CFL bulb. The key is to have enough brightness. A typical 9W LED bulb (60W incandescent equivalent) may not cover much area or intensity for microgreens - it could work for one small tray if placed very close. If you go this route, use multiple bulbs or a high-lumen bulb. Some people use screw-in LED "grow bulbs" which fit standard lamps; these often have a reflector design to focus light. They can work for a small growing area. Just keep expectations reasonable - if light is weak, microgreens will grow slowly and thinner.
Do microgreens prefer any particular light color (spectrum)? Not critically at this stage. They mostly need the blue and red parts of the spectrum for photosynthesis. White lights have those covered. Some growers experiment with pure red/blue "blurple" grow lights, but results show microgreens do just fine under broad-spectrum white and it's easier on the eyes too. Researchers have found that while certain spectra can slightly affect microgreen color or nutrient content, for basic growth, any adequate light will do.
Heat considerations: Traditional lights like incandescent or some fluorescents emit a lot of heat. This can dry out your microgreens or even "cook" them if too close. LEDs run much cooler. Keep this in mind if using, say, a high-power halogen work lamp (not recommended) - the heat could be detrimental. Always allow some airflow around lights and plants.
In summary, you do not need specialized plant lights for a few trays of microgreens. Many cost-effective lighting options exist. The primary goal is to ensure they get enough brightness for enough hours each day. Let's quantify that next.
How Many Hours and How Strong?
Microgreens, like most seedlings, thrive with long day lengths. They aren't grown long enough to be sensitive to photoperiod for flowering, so you don't need any dark-to-trigger blooms or such. Instead, more light generally equals better growth. Here are some guidelines:
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Minimum 6 hours, Ideal ~12-16 hours of light per day: While microgreens can survive on shorter light periods, they will grow slower and taller (stretching for light). A common recommendation is 12-16 hours of light daily for optimal growth. Many growers use 16 hours on, 8 hours off as a convenient cycle. Even 12 hours on/12 off can produce good results and some growers prefer it to give plants rest. It's been noted that microgreens can do fine with even 6-8 hours if that light is very strong (like direct sun or powerful lamp), but if using moderate artificial lights, aim toward the higher end. Plants do need some darkness - continuous 24-hour light is not necessary and can stress plants (they actually do a lot of growth processes in the dark). So give them at least a short night period.
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Light Intensity: We don't need precise PAR values here, but as a reference, microgreens will be happy with a light intensity of around 100-200 μmol/m²/s at canopy level (this is a measure used for plants). Practically, a 20W cool-white LED per 30×30 cm area, placed 20-30 cm above, will usually suffice. If using fluorescent tubes, two 24W tubes over a standard 10×20 inch tray is a common setup. If your microgreens are growing pale or extremely thin under your lights, it might indicate the lights aren't strong enough or are too far. Distance matters: light intensity drops off with the square of distance. So keep lights fairly close - typically 15-30 cm (6-12 inches) above the top of the microgreens is recommended. As they grow, you may need to adjust height. A good test: if you can clearly read by the light at tray level and it feels like bright daylight to your eyes, it's probably sufficient for plants.
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Avoiding Legginess: Leggy microgreens (tall, weak stems) result from low light. If you see this, increase either the duration or the intensity of light. Also check that they aren't too warm and crowded with not enough light, which exacerbates stretching. Proper lighting will produce shorter, sturdier stems and well-formed leaves. Leggy microgreens are not the end of the world - you can still eat them - but they might flop over or have less substance. Using a simple reflective surface (like placing a white poster board or foil behind your microgreens opposite a window) can help redirect more light onto plants if using sunlight.
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Signs of Too Much Light: It's rare with microgreens, but if using a very strong grow light extremely close, you might see drying out or even a slight bleaching of leaves (pale patches) - this could be light burn or heat from the lamp. Microgreens don't typically require such intense light that burning is an issue. If you suspect this, raise the light a bit or reduce the hours.
In short, treat microgreens similar to garden seedlings that need "full sun." Give them as much light as you reasonably can during their short life, and they will reward you with vibrant color and flavor.
Types of Lights - Which to Choose?
To answer the original question: Do you need a special plant light? If you have a sunny window, probably not. If you lack natural light, you have options:
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LED Shop Lights or T5 Fixtures: Highly recommended for beginners setting up more than one tray. They are energy-efficient and provide good coverage. Look for 5000-6500K ("daylight") specification. Position 20-30 cm above plants. These lights are relatively inexpensive and widely available. Connect to a timer for convenience.
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Household LED Bulbs with Clamp Lamp: If you're growing just a tiny batch on your desk, a 10-15W LED bulb in a reflector clamp lamp can do the trick. Use a cool-white bulb. You might need two lamps angled from different sides for even coverage. This is a very DIY approach but can work.
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Premium LED Grow Lights: If you already own one or plan to invest, you can certainly use it. Overkill won't harm (as long as you manage heat), and some growers like using high-end lights to possibly boost nutrient content or pigmentation slightly. Just remember, your microgreens will be harvested so soon that they won't use the far-red or UV diodes that some grow lights include to trigger flowering or such. But they will happily soak up the light anyway.
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Fluorescent Lights: T5 fluorescents were a staple for seedlings and microgreens for years. They still work well. Just mind that bulbs degrade (replace annually if used heavily) and they produce more heat. Keep a few inches distance from top of greens.
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Sunlight + Supplement: You can combine approaches. For example, set trays by a window and on dark days or evening hours use a lamp to hit your target light hours. This hybrid method can ensure your micros never lack light even if the sun is shy.
One more consideration: If you intend to scale up your microgreen growing (multiple shelves etc.), you might choose lighting based on efficiency and space. Many indoor growers use 4-foot LED strip lights attached under shelving. Some use multi-tier grow racks with each shelf lit. In such cases, thin LED bars that can daisy-chain are very handy. They minimize wiring clutter. Brands like Barrina (mentioned by some UK microgreen farmers) or others can connect 6-8 lights together in one run. This is more a convenience and aesthetic choice, but worth noting if you expand.
For now, if you're just starting: use what you have, and upgrade if you see the need. Many beginners are surprised at how well microgreens do with a basic light setup.
Managing Light for Healthy Growth (Tips & Tricks)
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Use a Timer: We mentioned it earlier, but it's worth repeating. A cheap outlet timer will ensure your microgreens get a consistent day/night cycle. You won't have to remember to turn lights on every morning. Set and forget - the consistency will yield consistent crops.
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Reflective Surfaces: If using artificial lights, consider lining the area with something white or reflective. Even a sheet of white poster board behind the trays can reflect light back onto plants. Mylar or foil can work too (though foil can create hot spots, white is often better). This maximizes the light use efficiency, especially in a small indoor setup.
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Distance Management: As microgreens grow, keep the lights at an appropriate distance. If they grow up close to a fluorescent tube, they might get a bit warm - raise the light. If they seem to be stretching (growing tall thin stems with a gap between soil and leaves), they might be too far - lower the light. A rule of thumb for LED bars: ~25 cm above canopy is usually good. For fluorescents, ~15 cm (but watch heat). For window light, ensure the tray is directly in the brightest spot, not set back in the room.
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Temperature & Light: Light and temperature often go hand in hand. Under strong lights, your growing area might be a couple degrees warmer. Generally fine (microgreens like ~20°C). But if you use an enclosure or grow tent with lights, monitor that it doesn't overheat. Conversely, if you turn lights off in a cool room, temp drops at night - typically also fine and can even intensify some colors in microgreens (some purple varieties get more vivid with cooler nights). Just avoid extremes.
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Watch for Color Cues: Healthy microgreens under proper light should be richly colored - green leaves should be green, purple varieties like red cabbage or purple radish should be deep purple. If colors are washed out or yellowish, that's a sign of not enough light (or possibly nutrient issues if you reused soil without any fertilizer, but usually light). Adjust lighting and they often green up within a day or two.
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Avoid Direct Sun Through Glass in Summer: One caution - while sunlight is great, through a closed window on a hot summer day it can get very hot (the glass creates a greenhouse effect). Microgreens can scorch or dry out quickly in such conditions. If you notice wilting on a sunny afternoon, it might be heat stress. Provide ventilation (open the window if possible) or move them a bit further from the glass during peak sun, or use a thin curtain to diffuse the intensity. They need light, but not 40°C heat in the tray.
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Dark Period Benefits: We've touched on giving a dark period. Some growers even do a second "blackout" just before harvest (putting the tray in darkness for 12-24 hours) to stimulate the plants to stretch slightly and potentially increase yield. This is optional - you can experiment once you're comfortable. Generally, continuous light beyond 18 hours doesn't yield much benefit and may waste electricity, so give them a rest at night.
To sum up, microgreens do need good light, but special lights are not a strict requirement. You can absolutely start with a sunny window or simple LEDs you have. The key is ensuring they get enough light each day. If your home setup can't provide that, then considering an affordable grow light is worthwhile - it can be as simple as a $20 LED shop light which will pay off in stronger, greener microgreens.
For a beginner, it's encouraging to know that microgreens are quite "flexible" with their lighting needs. They will grow under various light sources - maybe a bit taller here or there, but you will get a crop. As you refine your process, you might optimize lighting to improve yields or nutrition (for example, some studies suggest exposing microgreens to strong light can boost certain vitamins). But at the start, focus on the basics: give them lots of light hours, moderate intensity, and watch their response.
If you find that your space just doesn't get enough natural light, invest in a simple grow light setup - your microgreens will thank you with faster growth and a lush harvest. For detailed recommendations on specific lights and a deeper dive, you might check forums or our resources; however, for most home gardeners, the solutions above will suffice.
Lastly, keep in mind that other factors like water and airflow interact with lighting. Strong lights can dry out your growing medium faster, so be ready to water a bit more often (see our watering guide for tips on maintaining moisture). Good light also works in tandem with good air circulation to prevent issues like mold - light keeps plants vigorous, and a small fan will prevent excess humidity under intense light.
With this knowledge, you can confidently answer the question when someone asks "Do I need special lights for these?" - you'll know that any bright, cool-white light source can do the job for microgreens, and the real key is providing sufficient duration and positioning the lights properly. Now, go forth and let your microgreens bask in that light!