Microgreens are the young seedlings of edible vegetables and herbs, harvested just after the cotyledon leaves have fully developed, typically before the first true leaves appear. This brief growth stage, lasting one to three weeks, concentrates vitamins, minerals, and antioxidants, yielding a product significantly more nutrient-dense than its mature counterpart. Unlike sprouts, which are grown solely in water, microgreens require a growing medium and light for photosynthesis. Cultivating these miniature greens indoors is a simple way to add concentrated flavor and nutrition to your diet year-round.
Gathering the Essential Supplies
The foundation of a successful indoor microgreen setup begins with the correct containers and medium. You will need a set of shallow growing trays, ideally measuring 10 by 20 inches. One tray should feature drainage holes to hold the growing medium and allow excess water to escape, and a second tray should be completely solid for bottom watering later in the process.
For the growing medium, choose a light, soilless material like coco coir, peat moss, or a sterile seed-starting mix. Traditional potting soil is often too dense and holds excessive moisture, creating an environment for mold and fungal issues like damping off. Since the microgreens are harvested quickly, they draw sufficient nutrients from the seed itself, making added fertilizer unnecessary.
Finally, secure high-quality, untreated seeds specifically labeled for microgreen production to ensure a high germination rate. Beginners often find success with fast-growing varieties like radish, broccoli, and pea shoots, which germinate reliably and offer distinct flavors. A simple spray bottle or mister is necessary for the initial wetting of the seeds without disturbing their placement.
Sowing the Seeds and Initial Germination
The first step involves preparing the growing medium by adding water until it is evenly moist, resembling a wrung-out sponge. This pre-dampening ensures the seeds have immediate access to moisture. For larger seeds like peas and sunflowers, a pre-soak of 8 to 12 hours can accelerate germination. Next, broadcast the seeds thickly and evenly across the surface of the medium in a technique known as high-density seeding.
The seeding density is far greater than traditional planting, with smaller seeds requiring 10 to 15 seeds per square centimeter for a dense final crop. After seeding, the tray enters the blackout phase, covered with a solid lid or inverted tray to exclude all light. This period, typically lasting two to five days, forces the emerging seedlings to stretch upward in search of light, resulting in the long, straight stems desired for harvest.
Providing Light and Water for Continued Growth
Once the seedlings have lifted the cover and grown to about an inch tall, they are ready for bright light exposure. The greens require 12 to 16 hours of light daily to develop their cotyledon leaves and begin photosynthesis. Full-spectrum LED shop lights or T5 fluorescent fixtures are inexpensive options that provide the necessary light spectrum, ideally ranging from 4,000K to 6,500K to mimic natural daylight.
The light source should be positioned close to the plants, typically 6 to 12 inches above the canopy, to prevent the seedlings from becoming thin and “leggy”. At this stage, watering transitions entirely to bottom watering using the solid tray beneath the growing tray. Adding water to the bottom tray allows the medium to wick moisture upward, keeping the foliage dry to prevent mold growth and the fungal disease known as damping off.
Maintaining good air circulation is important to prevent a humid, stagnant environment that encourages fungal issues. A small, oscillating fan set to create a gentle breeze across the surface of the greens will help dry the medium’s surface and strengthen the stems.
Harvesting and Preparation for the Next Batch
Microgreens are ready for harvest when their cotyledon leaves are fully expanded and vibrant. Some varieties are harvested just as the first pair of true leaves begins to appear. This peak window, usually 7 to 21 days after planting, maximizes both the flavor profile and the concentrated nutrient content. Harvest should be done with sharp, clean scissors or a knife, making a single, swift cut just above the surface of the growing medium.
Cutting slightly above the soil line ensures that the final product is clean and free of any growing medium, roots, or seed hulls. For optimal freshness, harvest only what you plan to use immediately, as the greens remain freshest while still rooted in the tray. To store any excess, ensure the microgreens are completely dry and place them unwashed in an airtight container lined with a dry paper towel in the refrigerator. Since most microgreen varieties do not successfully regrow after being cut, discard the spent root mat and medium into a compost bin before starting a new batch.