Microgreens are the immature seedlings of edible vegetables and herbs, harvested just after the cotyledon leaves have developed. Broccoli microgreens are among the most popular varieties for home growers because they are exceptionally easy to cultivate and reach harvest readiness quickly. These tiny greens deliver a concentrated nutritional payload, offering up to 40 times the nutrients of their mature counterparts. They contain high levels of vitamins A, C, E, and K, along with minerals like iron and calcium.
Essential Supplies and Setup
Before planting, collect the necessary supplies. You will need at least two shallow growing trays: one with drainage holes for the growing medium and a second, solid tray to act as a water reservoir and blackout dome. The quality of your high-germination broccoli microgreen seeds is important for a dense, uniform harvest.
The growing medium should be a fine-textured substrate like coco coir, a seed-starting mix, or fine potting soil. This provides a stable, moisture-retaining base for the shallow root systems. While some growers use hydroponic mats, a soil-based medium is generally more forgiving for beginners. You will also need a simple spray bottle for initial misting and a small weight, such as a brick or a heavy book, for the germination phase.
Seeding and the Germination Phase
Fill the drainage tray with about one to one-and-a-half inches of growing medium, leveling and gently firming the surface to prevent dips where water can pool. Broccoli seeds are small enough that pre-soaking is not necessary, so you can proceed directly to sowing. The goal is to create a dense, carpet-like layer of seeds across the entire surface of the medium.
Spread the seeds as evenly as possible, aiming to cover the medium without creating excessive piles. Once sown, lightly mist the seeds and the surface of the medium with the spray bottle until everything is evenly damp. Place the second, solid tray directly on top of the seeded tray, and then place your small weight on top of the inverted cover.
This blackout period should last for two to four days. The darkness and the slight pressure encourage the seedlings to push their roots down into the soil while forcing the emerging sprouts to grow uniformly tall as they search for light. This process, called etiolation, promotes long, straight stems and a high-yield density. Remove the weight and cover once the seedlings have noticeably lifted the top tray, indicating they are ready for light exposure.
Providing Light and Ongoing Care
After the blackout phase, the pale, yellowish seedlings must be moved into a source of light to initiate photosynthesis and develop their characteristic green color. A sunny windowsill with indirect light is suitable, but for faster, more consistent growth, a simple fluorescent or LED grow light is preferred. Aim to provide the microgreens with between 12 and 18 hours of light each day.
The preferred method for watering shifts to bottom watering, or sub-irrigation, to prevent fungal issues like damping off. Place the drainage tray inside the solid reservoir tray and pour water into the bottom tray, allowing the medium to soak up moisture from below. This technique keeps the delicate stems and leaves dry, which is important for preventing mold growth, while ensuring the roots have access to water.
Remove the growing tray after about 15 to 30 minutes, once the surface of the medium feels moist, to prevent the roots from sitting in standing water. Re-water only when the growing medium begins to feel light or slightly dry to the touch. Maintaining good airflow around the tray is also recommended to help manage humidity and reduce the risk of mold.
Knowing When and How to Harvest
Broccoli microgreens are typically ready for harvest between seven and fourteen days after planting, depending on the growing conditions. The optimal time to cut them is when the cotyledons, which are the first small, rounded leaves, are fully expanded and vibrant green. Harvesting before the emergence of the first true leaves ensures the best flavor and highest concentration of nutrients.
Stop all watering about 12 hours before you plan to harvest to reduce the moisture content of the greens, which helps improve their shelf life after cutting. Use a clean, sharp knife or a pair of scissors to cut the stems just above the soil line. Avoid cutting into the soil itself to prevent contamination.
Once harvested, gently dry the microgreens of any surface moisture, either by patting them lightly or using a salad spinner. Store the dried microgreens in an airtight container in the refrigerator. Since broccoli microgreens will not successfully re-grow after being cut, the spent growing medium can be composted.