How to Grow Microgreens Indoors in Winter

Grow radish, broccoli, pea shoots, and other microgreens on a windowsill or under a shop light in 7 to 28 days. Trays, mix, light, watering, and harvest.

Published 2026-10-19 by ThriveThyme

microgreens indoor gardening winter pea shoots radish

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How to Grow Microgreens Indoors in Winter

Microgreens are young seedlings cut when the seed leaves open, usually 1 to 3 inches tall. Mississippi State University Extension groups them by speed: pea shoots and radish in about 7 to 10 days, brassicas like kale and cabbage in 10 to 15 days, and beets, chard, and cilantro in 16 to 25 days. They grow indoors, so your zone and frost date do not matter.

Use the Microgreens Desk to pick crops and a harvest date and get soak dates, sow dates, and seed weights.

What You Need

• A tray with drainage holes, plus a solid tray under it for bottom watering. A 10 x 20 inch tray is the standard size. A takeout clamshell with holes poked in the base works for a small batch.
• Seed-starting mix or coco coir, about 1 to 1.5 inches deep.
• Seed sold for sprouting or microgreens. Do not use treated garden seed with a colored coating.
• A bright window or a basic LED shop light.
• Clean scissors.

Steps

1. Moisten the mix, fill the tray, and press it flat.
2. Weigh seed for your tray. See how much microgreen seed per tray.
3. Soak large seed first if the crop calls for it. Peas take about 6 hours and sunflower about 12 hours in Utah State University Extension trials.
4. Scatter seed thickly and evenly. Press it into the surface. Do not bury small seed.
5. Mist, then cover with a second tray or lid. Keep it dark for the cover days listed on the Microgreens Desk. Add light weight on peas and sunflower so roots grip the mix.
6. Uncover when roots hold the mix and shoots push up. Move to light.
7. Bottom water from here on. Keep the mix damp, not soggy.
8. Harvest with scissors just above the mix. Rinse, store in the fridge, and eat within about a week.

Light in Winter

Winter window light is weak and short. A south window can work for fast crops. Under weak light, seedlings stretch, lean, and stay pale. Utah State keeps lights on 18 hours a day in its trials. A simple LED shop light a few inches above the tray for about 16 hours a day gives straighter, greener stems.

Temperature

Penn State Extension lists about 60 to 75 F for germination and 60 to 70 F air for growing. A normal heated room is fine. Avoid cold window glass at night and the top of a hot radiator.

Keep a Steady Supply

Most microgreens are a one-cut crop. Sow a new tray every week for a steady supply. The Microgreens Desk repeats sow dates weekly or every two weeks and totals the seed for the whole plan.

If a tray turns fuzzy or floppy, read why microgreens get moldy or leggy.