Microgreens are the edible seedlings of vegetables and herbs, harvested when they are only a few inches tall, typically before their first true leaves emerge. These tiny greens are popular for their concentrated flavor and high nutritional content, and they offer a fast-growing, fresh food source that is simple to cultivate indoors. Growing microgreens successfully requires specific materials and controlled environmental conditions, which differ significantly from traditional gardening methods. Understanding these requirements for seeds, containers, substrate, and climate control is the first step toward a consistent harvest.
Selecting High-Quality Microgreen Seeds
The process begins with selecting seeds specifically designated for microgreen production, as these are typically sold untreated. Standard garden seeds are often coated with fungicides or other chemical treatments, which must be avoided since microgreens are harvested within a short window of seven to twenty-one days. Reputable suppliers also test for high germination rates, ensuring that a majority of the seeds you sow will successfully sprout.
Microgreen seeds are sown much more densely than garden varieties, covering the entire surface of the growing medium for a thick canopy at harvest. This dense planting requires seeds to be purchased in bulk, as standard small packets are not economical for covering a full growing tray. Larger seeds, such as peas and sunflower, have hard seed coats and require pre-treatment. This involves soaking them in cool water for about eight to twelve hours before planting to initiate germination.
Essential Containers and Trays
The physical structure needed for microgreen growth revolves around a simple and effective two-tray system. This setup uses one shallow growing tray, which includes drainage holes, nested inside a second tray that has no drainage holes. Shallow trays, typically measuring one to two inches deep, are preferred because they reduce the amount of growing medium required. They also improve air circulation around the base of the plants, which helps prevent fungal issues.
The tray without drainage serves as a water reservoir for bottom-watering, the preferred method for hydrating the crop. This second tray also plays a dual role during the initial germination phase. An inverted tray or lid is placed on top of the seeds for a “blackout period,” which forces the seedlings to stretch as they search for light. This stretching results in a taller, straighter stem and ensures a uniform crop height before the tray is moved under lights.
Choosing the Right Growing Medium
Selecting the substrate is a foundational decision in microgreen cultivation, with options falling into two main categories: soil-based and soilless. Soil-based substrates, such as fine-textured organic potting mix or a blend with coco coir, offer a natural source of nutrients for the plant’s short life cycle. However, soil is inherently messier, heavier, and can increase the risk of mold if moisture retention is not managed carefully.
Soilless options, including mats made from hemp, paper, or cellulose, provide a cleaner, more lightweight alternative. These mats are inert, meaning they contain no nutrients, which simplifies the growing process and reduces the chances of introducing pests or pathogens. While soilless mats require the roots to rely solely on the seed’s stored energy and water, they are ideal for fast-growing varieties. Coco coir, made from coconut husk fibers, represents a middle ground, offering superior water retention and a finer texture than dense potting mix. Regardless of the choice, the medium must be sterile and fine-textured to accommodate dense seeding and facilitate rapid root establishment.
Environmental Conditions: Light, Water, and Airflow
Once the seeds are sown and the blackout period is complete, managing the environmental inputs is necessary for healthy development.
Light
Microgreens require twelve to sixteen hours of light daily to optimize photosynthesis and prevent the seedlings from becoming pale and “leggy.” Most indoor growers rely on artificial light sources, such as full-spectrum LED or fluorescent fixtures. The light source should have a high color temperature, ideally between 5,000 and 6,500 Kelvin, to mimic natural daylight and promote compact, vibrant growth.
Watering and Airflow
Watering is managed primarily through the bottom-watering technique to keep the delicate stems and leaves dry. The roots absorb water via capillary action from the reservoir tray below, which prevents the surface of the medium from remaining excessively wet and minimizes the risk of mold and fungal diseases. Only during the initial seeding phase is a gentle misting bottle used to settle the seeds and ensure moisture for germination.
Adequate airflow is provided by a small, oscillating fan running for several hours daily. This gentle air movement simulates a natural breeze, which strengthens the stems and aids in transpiration. Airflow helps prevent the conditions that lead to dampening-off disease and mold growth.