Short answer: soak 25 to 35 g of onion seed for 4 to 6 hours. Spread it on a 10 × 20 inch tray of moist soil, cover it with a lightly weighted tray, and keep it dark and damp for about a week. Uncover, give bright light, and water from below. Cut at 14 to 21 days and remove clinging hulls.
What are onion microgreens?
Onion (Allium cepa) seedlings grow as thin, hollow green shoots, often with the black seed hull still attached at the tip. The flavour is sharp and fresh. Sprouting.com gives onion 10 to 14 days as sprouts and 14 to 21 as microgreens.1
How to grow onion microgreens
- Day0
Soak
Soak the seed for 4 to 6 hours. Drain.
- Day0
Sow
Spread the seed evenly over moist potting mix and press it in.
- Day0–7
Weighted blackout
Cover with a tray and a light weight. Mist daily.
- Day7
Light
Uncover once shoots stand up. Give bright light.
- Day14–21
Harvest
Mist, brush off hulls, and cut above the soil.
Onion sprouts
Onion seed can be sprouted in a jar, but it's slow: about 10 to 14 days. Most people prefer to grow it on soil as microgreens.
Problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Hulls stuck on tips | Normal | Weighted blackout, mist and pick off |
| Patchy start | Seed dried out | Keep damp during the long blackout |
| Mold | Too wet, still air | Water from below, ventilate |
Tips for growing onion microgreens
- Sow thickly. About 25 to 35 g per 10 × 20 inch tray gives a dense, grass-like tray.
- Use a weighted blackout for about a week to help shed the black seed hulls.
- Keep it damp. The long start is the riskiest time for drying out.
- Give bright light so the thin shoots stand upright.
Onion vs leek vs garlic chives
| Microgreen | Flavour | Best use |
|---|---|---|
| Onion | Sharp, like scallion | Tacos, burgers, potatoes |
| Leek | Mild and sweet | Soups, eggs, fish |
| Garlic chives | Mild garlic | Dumplings, noodles, fried rice |
How to use onion microgreens
Use onion microgreens anywhere you'd use sliced scallions or chives. They suit baked potatoes with sour cream, tacos, burgers, deviled eggs, omelettes, ramen and salads. A small pinch gives a lot of flavour.
Storing and eating
Use within 5 to 7 days. Sprinkle onion microgreens on tacos, baked potatoes, eggs, soups and burgers.
Onion FAQ
How long do onion microgreens take?
About 14 to 21 days on soil. Onion sprouts in a jar take 10 to 14 days, much slower than most sprouts.
Do onion microgreens taste like onion?
Yes. They're sharp and fresh, like a strong scallion. Use them in small amounts.
Why do onion microgreens have black tips?
Those are the seed hulls, which cling to the shoots. Mist the tray and brush or pick them off before eating.
Can I use onion microgreens instead of scallions?
Yes. They have a similar sharp onion flavour and work as a garnish wherever you'd use scallions or chives.
Written by Michael
A passionate sprouting professional sharing practical tips for growing sprouts and microgreens at home. More about Michael
Sources
- Sprouting.com (Mumm's Sprouting Seeds). Product pages: days to sprout, soak time and yield for each seed. Link
