Follow the planting instructions for each variety of seeds. For instance, some seeds prefer to be sown on the surface of the soil, while others need to be covered. We recommend using sterilized seed starting soil in shallow trays that have drainage holes at the bottom. You could try growing microgreens in 12-cell plug inserts that have been inserted into seedling germination trays. You can also grow microgreens in recycled plastic containers or clamshell packaging, as long as you poke some drainage holes in the bottom. Using a seedling warmer will increase the speed of germination, but it is not strictly necessary.
Spread the sterilized soil to a depth of only 2-3 inches. You’ll be harvesting the baby seedlings, so they don’t need a lot of room to grow roots.
Sow microgreen seeds fairly densely, a little less dense for large seeds like sunflowers or Swiss chard. Once your microgreen seeds have been planted, mist the whole area. You want to keep the soil moist like a wrung out sponge, but not sitting in water. Keep your mist sprayer handy, and spritz the soil regularly. The nice thing about using seedling germination trays is that you can take a second tray and invert it over the planted tray. This traps moisture inside, and prevents rapid evaporation.
As soon as the first sprout is visible above the soil, remove the tray from the seedling warmer (if using), and remove the cover (if using). Bright light is essential for growing microgreens. From late spring to early autumn, microgreens can be grown outdoors under daylight conditions. But indoors, you will need to provide some kind of supplemental light, particularly in the short, dim days of winter. The Growlight Garden is one of the best microgreen growing systems we have found. It even has a self-watering mechanism, which makes the whole process much easier. But any way you can provide light from T5 fluourescent tubes or other grow lights will work. Aim for full spectrum lights.
This bright light will help keep your microgreens short and stout. When light is insufficient, the sprouts will grow long and spindly.
Microgreens can be pulled from the soil and rinsed until all the soil particles have washed away. They can be enjoyed whole, roots and all. Or simply trim them with scissors and dispose of the used soil in your compost.
Microgreens are intended to be harvested when the first leaf pair (the cotyledon, or seed leaf) opens fully and turns green. This is the point at which your microgreens will be richest in nutrients. However, you can also let the seedlings continue to grow and harvest them as needed. Be aware that the longer they are left to grow the more roots will also develop in the soil.