Microgreens are young, edible seedlings of vegetables and herbs, typically harvested when one to three inches tall, shortly after the first set of cotyledon leaves develop. They offer a concentrated burst of flavor and nutrients, often containing higher levels of vitamins and antioxidants than their mature counterparts. Cultivating these greens outdoors allows them to benefit from natural sunlight and air circulation, which enhances their flavor profile and reduces the risk of mold common in indoor setups. Growing microgreens outside is an easy, cost-effective way to produce fresh, nutrient-dense additions for salads, sandwiches, and garnishes.
Selecting the Ideal Outdoor Environment
The success of outdoor microgreen cultivation depends heavily on selecting the correct location. Microgreens thrive in moderate temperatures, ideally between 59°F and 77°F (15°C to 25°C), and must be protected from extreme heat or cold. This means growing them outdoors only during the milder spring, summer, and fall months, or bringing the trays inside if nighttime temperatures drop below 40°F.
While microgreens need abundant light for robust growth, intense, direct midday sun can be too harsh and cause scorching. Positioning trays where they receive full sun in the morning and partial shade in the afternoon is the best compromise. Placing trays near a wall or under a light shade cloth provides a simple windbreak and shields the delicate seedlings from heavy rain, which can damage the plants and lead to soil splash. A physical barrier, such as a wire mesh or small enclosure, is necessary to protect the crop from common outdoor pests like slugs, birds, and rodents.
Preparing Containers and Growing Medium
Microgreens do not develop extensive root systems, making them ideal for growing in shallow containers rather than deep pots. Trays should be approximately one to three inches deep and must feature adequate drainage holes to prevent waterlogging, a common cause of failure. Use a second, solid tray without holes underneath the growing tray to facilitate bottom watering and collect excess runoff.
The growing medium needs to be light, sterile, and well-draining, as the seedlings rely on the nutrients stored within the seed itself. A sterile seed-starting mix, fine-textured potting mix, or a soilless blend of peat moss or coconut coir is recommended. Avoid rich garden soil or heavy potting soil, as it can be too dense and may introduce pathogens. Fill the container nearly to the top with the medium and lightly tamp it down to create a flat, even surface for sowing.
Sowing, Watering, and Ongoing Care
Seed density is crucial: cover the medium densely with a single, uniform layer of seeds without significant overlap. This high density maximizes yield and encourages seedlings to grow straight upward as they compete for light. After sowing, lightly mist the seeds with water to settle them in, ensuring the medium is moist but not saturated.
Many microgreen varieties benefit from an initial “blackout” period immediately after seeding. The tray is covered and kept in the dark for three to five days to encourage uniform germination and strong stem development. Some growers place a small weight on top of the cover for a day or two to strengthen roots and stems. Once the seeds have germinated and the seedlings push against the cover, remove it and move the tray to its selected outdoor location.
Watering is best done using the bottom-watering method, pouring water into the solid tray beneath the growing tray. This allows the medium to wick up moisture from below, preventing wetting of the delicate foliage. Bottom watering minimizes the risk of fungal issues like damping-off and mold, a concern in humid outdoor conditions. Keep the medium consistently damp, like a wrung-out sponge, and water only when the growing tray feels noticeably lighter. Good airflow is important for preventing stagnant moisture around the plants.
Harvesting and Storage Techniques
Microgreens are typically ready for harvest between one and three weeks after sowing, depending on the variety. The main indicator is the development of the first set of true leaves. Harvesting should occur when the plants are about two inches tall and before they become leggy or crowded, which diminishes their quality.
To harvest, use a clean, sharp knife or scissors to cut the stems just above the soil line, ensuring no growing medium is collected. Since microgreens are highly perishable, harvest them immediately before use. If storage is necessary, gently rinse the cut greens with cool water and dry them thoroughly using a salad spinner or clean paper towels, as excess moisture quickly leads to spoilage. Store the fully dried microgreens in a sealed, food-grade container lined with a paper towel in the refrigerator.