Short answer: microgreens need 12 to 16 hours of bright light a day after blackout. A sunny, south-facing window can be enough in summer. For winter, north-facing rooms or shelves, use a white LED shop light (5000 to 6500K) about 2 to 6 inches above the tray on a timer.
Do microgreens need a grow light?
Microgreens grow in the dark for the first 2 to 4 days. After that, they need light to turn green and grow sturdy stems. Without enough light, they stretch toward the window, turn pale yellow and fall over.
Whether you need a grow light depends on your window:
| Light source | Works? | Notes |
|---|---|---|
| South-facing window, summer | Usually yes | Turn the tray daily so it doesn't lean |
| East or west window | Sometimes | Fine for fast crops in summer |
| North window or winter light | Rarely | Expect leggy greens |
| Shelf, counter or basement | No | Needs a grow light |
| LED shop light | Yes | The easiest, most reliable option |
Choosing a microgreens grow light
You don't need an expensive grow light. Microgreens are only grown for a week or two and are harvested before they need strong light.
- Type: a full-spectrum white LED shop light or LED panel.
- Colour temperature: about 5000 to 6500K (marked "daylight").
- Size: about the length of your tray. A 2 ft (60 cm) light covers one 10 × 20 inch tray.
- Heat: LEDs run cool, so they can sit close.
How to set up a grow light
- Hang it 2 to 6 inches (5 to 15 cm) above the tops of the microgreens.
- Use a timer for 12 to 16 hours on, the rest off.
- Raise it as the greens grow, or if leaves look bleached.
- Add reflectors if you like. White card or foil around the shelf bounces more light.
A simple wire shelf with one light per shelf makes a compact home setup. See DIY vertical microgreen rack.
Signs your microgreens need more light
- Tall, thin, pale stems
- Greens leaning hard toward a window
- Yellow leaves a day or more after uncovering
- Weak stems that flop over
Signs of too much light or heat
- Bleached or crispy leaf edges
- Soil drying out very fast
Raise the light or move the tray a little farther from a hot window.
Light and colour
Red and purple microgreens, like red cabbage, red kale and Triton radish, develop stronger colour under bright light. A dim window gives greener, paler results.
More than a microgreens grow light
Light is just one factor. Warmth (65 to 75°F), airflow and bottom watering matter too. If your greens still struggle, read microgreen mistakes. For a full walkthrough, see the step-by-step microgreens guide.
Frequently asked questions
Do microgreens need a grow light?
Not always. A bright, south-facing window can work, especially in summer. If your microgreens grow tall, pale and floppy, they need more light, and an LED is the easiest fix.
How many hours of light do microgreens need?
About 12 to 16 hours a day after blackout. A cheap outlet timer makes this easy. They don't need light during the blackout stage.
How far should a grow light be from microgreens?
For a typical LED shop light, about 2 to 6 inches (5 to 15 cm) above the tops. Check the light's own guidance, and raise it if leaves look bleached.
Can I use a regular LED bulb for microgreens?
A bright LED shop light or panel works well. A single household bulb is usually too weak and too far away. Look for white light marked 5000 to 6500K.
Written by Michael
A passionate sprouting professional sharing practical tips for growing sprouts and microgreens at home. More about Michael
