How to Grow Microgreens Indoors (7-Day Harvest)

Microgreens are the fastest crop in gardening: seed to harvest in 7–14 days, on a kitchen counter, with almost no equipment. These tiny seedlings of vegetables and herbs concentrate flavor — arugula microgreens taste intensely peppery, radish greens add a sharp bite, and sunflower shoots are nutty and crunchy. Because you harvest the whole seedling just above the soil line, a single 1020 tray can yield a pound or more of greens from a tablespoon or two of seed. Here is the simple 7-day system that works indoors, year-round, with no grow tent required.

What You Will Need

• Microgreen seeds (radish, broccoli, arugula, sunflower, pea — or a mix)
• Shallow trays with drainage holes plus a solid tray underneath
• A lightweight growing medium — seed-starting mix, coco coir, or a soil-free mix
• A spray bottle for gentle watering
• A small grow light (optional but recommended for winter)

Step 1: Choose Your Seeds and Soak if Needed

Not all seeds are equal for microgreens. Radish, broccoli, cabbage, and arugula germinate fast and need no pre-soaking. Sunflower and pea seeds have hard coats and benefit from a 6–12 hour soak before planting. Buy seed labeled for sprouting or microgreens when you can — it is tested for clean germination. Start with a fast, forgiving crop like radish or broccoli mix for your first tray.

Step 2: Set Up the Tray

Fill a tray with drainage holes to about 1–1.5 inches deep with moistened growing medium. Press it down gently to level it — microgreen roots are shallow, so a firm, even surface gives uniform growth. Do not compress it into concrete; a gentle pat is enough.

Step 3: Sow Thickly, Not Deeply

This is the biggest mental shift from regular gardening: microgreens are sown so densely that the seeds nearly touch. Scatter seed evenly across the surface — roughly 1 to 2 tablespoons for a standard 10×20 tray, more for large seeds like peas and sunflowers. Press the seeds gently into the surface so they make full contact with the medium, then mist well with your spray bottle. Do not bury them; most microgreen seed germinates on the surface or under a light dusting.

Step 4: The Blackout Phase (Days 1–3)

For the first few days, seeds want darkness, warmth, and moisture — not light. Cover the tray with an inverted solid tray or a dark lid, or stack trays, to create a dark, humid microclimate. Check daily and mist if the surface looks dry. Most seeds germinate within 24–72 hours, and you will see a carpet of white and pale-green seedlings pushing up.

Step 5: Bring on the Light (Days 3–7)

Once most seeds have sprouted, remove the cover and move the tray into bright light. A sunny windowsill works in spring and summer; in winter, a basic LED grow light a few inches above the tray makes the difference between pale, leggy microgreens and sturdy, colorful ones. Keep the light on 12–16 hours a day. Water from the bottom by adding water to the solid tray underneath, so the medium wicks moisture up without knocking seedlings over.

Step 6: Harvest at the Right Height

Most microgreens are ready in 7–14 days, when the first true leaves appear (or, for peas and sunflowers, when the shoots are 2–3 inches tall). Harvest with clean scissors, cutting just above the soil line. Rinse gently and pat dry, then use immediately — they are best fresh. One tray gives a single harvest; after cutting, compost the spent medium and roots and start again. That spent medium is a perfect addition to a compost pile, which you can learn to manage in our compost pile guide.

Common Mistakes to Avoid

• Sowing too thin. Microgreens look sparse at one seed per inch; sow densely for a full carpet.
• Letting the tray dry out. Seedlings die fast without moisture. Check twice daily during the blackout phase.
• Leaving the cover on too long. Once sprouted, seedlings stretch for light and fall over. Remove the cover on day 2–3.
• Watering from above after sprouting. Top watering mats the delicate stems down. Switch to bottom watering.

FAQ

Do microgreens need sunlight or grow lights?

Bright sunlight works in the growing season, but a basic LED grow light gives consistent, predictable results all year. Even a low-cost panel a few inches above the tray is enough.

Can I grow microgreens without soil?

Yes. Coco coir, hemp mats, and other soil-free media work well and are less messy indoors. The method is the same: moist medium, dense sowing, dark start, then light.

Are microgreens the same as sprouts?

No. Sprouts are eaten whole, seed and all, grown in water with no light and no soil. Microgreens are grown in a medium, harvested above the soil line with scissors, and have only the seed leaves or first true leaves.

How many times can I harvest a microgreen tray?

Once. Cut the tray at soil level and compost the rest. Because they are so fast (a new tray every 7–14 days), continuous production is easy with two or three trays in rotation.

Bottom Line

Microgreens are the perfect gateway crop for indoor growing: cheap, fast, and genuinely delicious. Soak the big seeds, sow densely on moist medium, keep them dark for two to three days, then flood them with light and harvest in about a week. Start with a microgreen seed variety pack, drainable 1020 trays, and a bag of coco coir, and you will be snipping your first harvest before the seed packet even leaves the counter.

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