“Sprouts grown in soil” refers to the cultivation of plants harvested at an early stage, scientifically known as microgreens. Growing them in a specialized soil mix or soilless medium allows the plants to develop cotyledon leaves and sometimes the first true leaves, concentrating flavor and nutrients. This soil-based approach is favored for producing cleaner, fuller-flavored greens and for its ease of scaling up small, indoor growing operations.
Essential Materials and Seed Selection
Shallow containers, typically 10×20 inches, are ideal for microgreens. They do not require significant soil depth, with one to two inches being sufficient for their short growth cycle. These trays should be paired with a solid tray underneath to facilitate bottom watering and prevent spills. A fine-textured, sterile seed starting mix or coconut coir is highly recommended due to its excellent water retention and drainage properties. Heavy garden soil should be avoided because it often retains too much moisture and can compact easily, inhibiting delicate root systems.
Selecting the right seeds is crucial. Fast-growing and beginner-friendly varieties include broccoli, radish, and pea shoots, offering a range of flavors from mild to spicy. Larger seeds, such as sunflowers and peas, benefit from a pre-soak, while smaller seeds like broccoli and radish can be sown directly. Always source seeds specifically intended for microgreen production, as they often have higher germination rates and have not been treated with chemicals.
The Step-by-Step Sowing and Growth Process
The growing cycle begins with seed preparation. Larger seeds like peas or sunflowers should be soaked in cool water for 8 to 12 hours to break down their hard seed coats and initiate germination. After soaking, rinse these seeds thoroughly and allow them to drain before spreading them onto the growing medium. Fill the shallow tray with the prepared medium, level it, and lightly firm it down to create an even surface. Moisten the medium thoroughly until it is uniformly damp, but not waterlogged, prior to sowing.
A dense sowing technique is necessary to achieve a full tray of microgreens. Scatter the seeds so they cover the entire surface, touching one another but not heavily clumped or layered. This high seed density maximizes yield but requires careful management to prevent mold. For most varieties, gently press the seeds into the surface without covering them with additional soil. Once sown, mist the seeds and medium again with a spray bottle to ensure surface moisture without disturbing the seeds.
The crucial next phase is the “blackout” period, where the planted tray is covered with an opaque lid or another tray to simulate darkness. This encourages uniform germination and prompts seedlings to stretch for light, resulting in taller, more uniform stems. This period typically lasts for two to four days. During this time, the seeds must remain moist, which can be maintained by the enclosed humidity or by lightly misting the surface if it appears dry. Transition the tray to light once the sprouts have anchored their roots and the stems begin to push against the cover.
Seedlings require six to eight hours of direct light daily to develop chlorophyll and turn a vibrant green. Ideally, use a dedicated grow light positioned a few inches above the tray. If relying on a windowsill, supplemental lighting is often necessary to prevent the plants from becoming “leggy” or weak. Switch from misting to bottom watering at this stage. Add about a quarter-inch of water to the solid bottom tray, allowing the medium to wick up moisture for 10 to 15 minutes, which minimizes the risk of fungal issues by keeping the leaves dry.
Harvesting Techniques and Troubleshooting
Microgreens are ready for harvest when they have fully developed their cotyledons and often when the first set of true leaves begins to appear. This stage typically occurs between 7 and 21 days after sowing, depending on the specific variety. Fast-growing types like radish and broccoli are usually ready around the 10 to 14-day mark. Delaying the harvest allows for greater nutrient concentration and flavor development, but waiting too long can lead to a less tender texture.
Harvesting involves using a sharp knife or clean scissors to make a single, clean cut just above the soil line. Cutting too low risks incorporating planting medium into the harvest, while cutting too high leaves usable stem material behind. Once harvested, gently rinse the greens in cool water and thoroughly pat or spin them dry, as excess moisture dramatically reduces shelf life. For storage, place the dried microgreens in an airtight container lined with a paper towel and refrigerate, where they can remain fresh for up to a week.
Preventing Mold and Fungus
One of the most common issues when growing microgreens is the appearance of mold or fungus, often caused by overwatering, poor air circulation, or excessive seeding density. True mold appears as fuzzy, cobweb-like growth on the soil surface or stems. This should not be confused with the fine, white root hairs that naturally form at the base of the seedlings. Increasing airflow with a small fan and ensuring the growing medium is only damp, not saturated, are the best preventative measures.
Addressing Growth Issues
Uneven germination is a frequent problem that can often be resolved by ensuring a consistent blackout period and maintaining even moisture across the entire tray surface before the seeds sprout. If the seedlings appear wilted or floppy, they are likely suffering from a lack of water. They will often perk up quickly after a thorough bottom watering.