Microgreens are the edible young seedlings of various vegetables and herbs, typically harvested shortly after the first true leaves emerge. Cultivating these greens indoors offers the advantage of a year-round harvest, regardless of external weather conditions. These tiny plants are highly prized for their concentrated nutritional profile, often containing significantly higher levels of vitamins, minerals, and antioxidants compared to their mature counterparts.
Gathering Necessary Supplies
A successful indoor setup requires a two-tray system. You will need one shallow 10×20 inch tray with drainage holes to hold the growing medium and a second, solid tray without holes to catch excess water and facilitate bottom watering. The choice of growing medium is flexible, with options like fine-grained soil mix, coco coir, or specialized hemp mats. Soil-based mediums tend to retain moisture well, while soilless options reduce the potential for mess and soil-borne pathogens.
The seeds themselves must be untreated, and it is important to purchase seed varieties specifically labeled for microgreen use to ensure a high germination rate at dense sowing levels. For lighting, a south-facing windowsill can suffice, but consistent results require supplemental light sources. Basic LED or T5 fluorescent grow lights are highly effective, providing the full spectrum light that promotes healthy growth without producing excessive heat. These lights should have a color temperature around 6500 Kelvin to mimic natural daylight.
Preparing the Medium and Sowing Seeds
Prepare the growing medium by moistening it thoroughly until it is uniformly damp, but not saturated. After leveling the medium in the tray, the seeds are scattered densely across the entire surface to create a thick, continuous layer, which is a departure from traditional garden spacing. The exact seeding rate varies by variety; for example, a 10×20 inch tray requires approximately 50 grams of broccoli seed but significantly more for peas or sunflowers.
The seeds are not covered with any additional growing medium; they will push their way down to anchor themselves. Following sowing, a thorough misting helps settle the seeds onto the surface and initiates the germination process. The tray is then placed in a blackout phase for two to four days by covering or stacking it. This period encourages uniform germination and stem elongation, leading to the taller, paler stems desired for microgreens.
Managing Light and Water for Growth
The blackout cover is removed once the seedlings have uniformly lifted the tray or reached a height of about one to two inches, appearing pale yellow or white. They are immediately transitioned to the light source to begin greening up and developing chlorophyll. The grow lights should be positioned approximately six to twelve inches above the emerging seedlings to provide sufficient intensity without causing heat stress or burning the delicate leaves.
Microgreens thrive under a light cycle of 12 to 16 hours per day, followed by a period of darkness. Watering is best managed using the bottom watering method, where water is poured directly into the solid tray beneath the growing medium. This technique allows the roots to wick up the moisture they need, preventing the leaves and stems from getting wet, which significantly reduces the risk of fungal growth and mold formation. The medium should remain consistently moist throughout the growth phase, but never submerged in standing water.
Harvesting and Post-Harvest Handling
Microgreens are ready for harvest once they have developed their cotyledons, the initial seed leaves, and in some cases, the first true leaves, usually around seven to fourteen days after sowing. Harvesting at this stage ensures the highest concentration of flavor and nutrient content. The best time for cutting is typically in the morning, when the greens are most hydrated and crisp from the night’s rest.
To harvest, use a clean, sharp knife or a pair of scissors to cut the stems just above the surface of the growing medium, being careful not to disturb the soil or mat. Cutting too close to the medium can introduce contaminants into the final product. After cutting, the microgreens should be gently dried thoroughly to prevent premature spoilage and maintain freshness. Storing the dried greens in an airtight container in the refrigerator, ideally between 35 and 40 degrees Fahrenheit, helps them retain their quality for up to a week.