Lighting & Lumens: Understanding Microgreens Light Requirements

Oct 15

3 min read

They Say It Is Darkest Just Before Dawn 🌅🌱

4:30 AM: "0 dark 30" as my dad used to say. Sunrise or dawn is typically between 6:00 AM and 7:30 AM depending on where you call home. So when the microgreens start their workday here at Tasty Little Leaves Microgreens at 5:00 AM, it is still pitch black dark outside.

As you may or may not know, plants work by converting sunlight, water, and carbon dioxide into oxygen and energy-rich sugars. This process is called photosynthesis. Without all of the elements, plants cannot grow. So we need to keep the lights on around here. But what type of light, how much light, and for how long? What are the light requirements?

The Power Setup: 6500K & 2,200 Lumens 💡

Sunlight is unpredictable. Weather is fickle. Sunny, overcast, rain. It is a gamble what you are going to get. Just ask the weather forecaster for a prediction, and they get it wrong half the time. Plus, the filtered light that comes through the window is not enough to get the microgreens to grow consistently. They will not be straight because they are reaching toward the window across the room.

Enter a controlled grow environment! Light, air, and temperature are all controlled in our grow room. Plants grow on racks as pictured above. (Oh, by the way. See that tray on the bottom rack that has yellow stems. It was taken out of germination the morning this picture was taken. While they are in the dark cycle, plants cannot produce chlorophyll, which is how they get their vibrant green coloring.) Each tier on our wire racks have fans, timers, and lights.

The lights include three 4-foot LED T5 light strips:

6500K (Daylight Spectrum): This crisp, cool-white light mimics peak midday sun. It tells the plants, "It’s prime time to photosynthesize!"
2,200 Lumens Per Bulb: That’s a serious punch of brightness! Microgreens take anywhere from 7 to 24 days from seed to harvest. Once out of germination, our crops stay under these intense lights for 4 to 18 days to build maximum nutrients and vibrant color quickly. All of our crops need intense light to build up maximum nutrients and vibrant color quickly.

No "Leggy" Greens: Without strong overhead lighting, seedlings stretch out tall, thin, and pale searching for light. Heavy light keeps them compact and sturdy.

The 17/7 Sleep Schedule: Microgreens Light Requirements

Believe it or not, plants need their beauty sleep just like we do!

17 Hours ON: The lights run for 17 straight hours, giving the seedlings all the light energy they can process in a day. And I thought my 8-10 hour corporate work hours were long!
7 Hours OFF: When the lights turn off, the microgreens shift gears. During these 7 hours of darkness, they rest, process the energy they made during the day, and build strong cell walls and roots.

Our Secret Weapon: Timers! ⏰

Could we flip the switches manually at 5:00 AM every morning and turn them off at 10:00 PM every night? Sure thing! And I did when I first started growing... but I was never consistent. One day I got them on at 9:00 AM, then another at 6:00 AM. Then I had an early appointment and didn't get the lights turned out before I headed out the door!

At night, I'd stay up until 10:00 PM one night, and the next three I was exhausted and heading to bed by 8:45 PM. The lights went out early. I didn't have it in me to keep the lights on! The results were uneven growth, hot spots, leggy stems and bland flavor.

Microgreens light requirements matter. Consistent hours of light/dark are essential for even growth, appropriate crop yields, and flavor intensity. I had to find a way to control the on/off switch and take me out of the equation. Upgrading the grow racks with automated timers was the answer.

Those timers now keep our 17/7 schedule running smoothly 365 days a year so every batch gets the exact same premium treatment.