How to Grow Onion Microgreens Fast and Easy

From winter to bunching to green, there are tons of cool onion varieties. They may be different colors and have different flavors, but all have one thing in common: onions make great microgreens! Onion microgreens are low-maintenance, tasty, and the perfect new garden project.

If you haven’t tried growing microgreens yet, it’s definitely worth a shot. A microgreen, like a sprout, is a young plant that’s harvested early for its tender flavor and surplus of nutrients. Unlike sprouts though, microgreens are grown until they develop their first leaves (cotyledons), which optimizes its culinary characteristics.

Onion microgreens are one of the more unique-looking choices. These long, skinny greens hang onto their black seed husks, which gives them a polka-dotted look. The husks are edible and said to have a garlic taste. The onion microgreens themselves are savory and have a stronger onion flavor than you’d think. They taste delicious when prepared like chives or chopped green onions.

Onion microgreens are very easy to grow, but they grow slowly (you may want a faster plant if this is your first time growing microgreens). It’ll be anywhere from 12-21 days until these fresh greens are ready to harvest. Once the time comes, these onions will definitely be worth it!

Good Products At Amazon For Growing Onion Microgreens:

• Hydrofarm Agrobrite T5 Grow Light
• 10″x20″ Growing Trays
• Plant Misting Bottle

Onion Microgreens Quick Info

Growing Onion Microgreens

Onion microgreens need the same materials as any microgreen to grow. Most of these can be reused so you can experiment with other microgreen types later on.

Materials

• Seeds: any type of onion seed (we especially like the quality seed from True Leaf Market)
• Container: at least two shallow containers that can have holes poked in them, like these
• Growing medium: Espoma seed starter mix or coconut coir
• Light: we’ve had success with the Agrobrite T5 grow light, but you can definitely check out our other favorites
• Spray bottle
• Kitchen shears

And because we mentioned True Leaf Market’s onion seed before, let’s share some of our favorites:

• Crystal White Wax onion microgreens seeds
• Organic Evergreen Bunching onion microgreens seeds
• Red Burgundy onion microgreens seeds
• Southport Red Globe onion microgreens seeds
• Tokyo Long White Bunching onion microgreens seeds
• Utah Yellow Sweet Spanish onion microgreens seeds
• White Sweet Spanish onion microgreens seeds

You might be wondering: don’t onions grow from bulbs, not seeds? It turns out that these plants can do either one, but seeds are the most efficient for onion microgreens – especially since we want to grow them close together. Since the seeds are so small and they’ll be densely planted in the soil, you may want to buy them in bulk. You’ll need at least half an ounce of seeds per 10×20” tray of soil.

Although seeds are the norm, you can still plant bulb sets instead for larger onions. Be aware that bulbs will not produce grass-thin microgreens as seeds do. If you want to give this a try, we recommend checking out our article on planting onions.

Seed-starting soil is usually the best for micro greens growing. However, onion microgreens will also grow well in coconut coir. This medium will retain moisture better than soil so you don’t have to water as often.

Soaking

Onion seeds are teeny and don’t have to be soaked before planting. But, a couple hours submerged in water may help them germinate faster, so it’s up to you.

Planting

We want to grow onion microgreens like a dense mat of grass. This saves space and optimizes our harvest. To start, punch some water-drainage holes in a growing tray and fill it almost to the brim with soil. Pack the soil down and wet it with the spray bottle. We’re now ready to start planting seeds!

Spread your microgreens seeds all over the soil surface, including the corners of the tray (you may want to use a shaker bottle). The seeds should be close together. However, you have to ensure that they aren’t actually touching each other. When they grow too closely, onion seeds create the perfect habitat for fungal growth in the soil. Leave the seeds exposed instead of covering them with soil.

After planting, give your onion seeds a good spritz of water for germination and then place the second tray directly on top of them (right side up). This creates a blackout for the onion seeds to germinate in while also pressing them into the soil. You can even add up to 5 pounds of weight to the cover to ensure no light gets through to the seeds. After germination, when the onion microgreens start growing, they’ll collectively push up the cover and weight.

Growing

Keep your planted seeds in the dark for at least 3-4 days. They likely won’t need watering during this time. When the seeds grow into seedlings and have yellow coloring, you can remove the seed cover. The sprouts may seem squished down at first, but they’ll quickly stand up (and turn green) in the light.

Place your onion microgreens directly under the grow light. We prefer artificial light for indoors microgreen growing because the shoots grow towards the light. If the trays are simply placed on a windowsill, the microgreens will grow unevenly. With a grow light, you’ll also be able to control exactly how much light the trays get each day (we recommend 8-12 hours).

Remember how we’re trying to prevent fungus growth? Perhaps the most important precaution we can take is bottom-watering the tray. This keeps the microgreens dry and less inviting to fungi spread.

To water from the bottom, grab your second tray. Fill it with a couple inches of water and set the growing tray inside it. Let the soil drink up the water for about 10 minutes and then remove it. Repeat this watering process whenever the soil starts to dry out. 

Harvesting

Onion microgreens have a larger window than most for harvesting. You’ll be able to harvest bit by bit instead of all at once (though you can certainly do just one big harvest). However, take note that the microgreen flavor will change as they mature so you don’t want to wait too long. Sometimes, the onion microgreens also dry out on the tips as they keep growing.

Begin harvesting your onion microgreens when they’re 4 inches tall and start leaning over (they’ll look like un-mowed grass). Using clean kitchen shears (or something similar) clip the onion microgreens in bunches at least ½ inch above the soil surface.

Onions grow from the bottom of the stem instead of the top. This means we can squeeze a second harvest out of the trays. Just keep caring for the microgreens until they regrow and can be harvested again.

Storing

After the harvest, hold off on washing the onion microgreens until you’re about to use them. As mentioned earlier, you can keep the seed husks on or remove them from the onions. Whichever you choose, each delicious green will provide an excellent, no-hassle, onion flavor (they won’t even make you cry when you chop them!).

Keep your microgreens, onion or other, in a sealed container in the fridge. They should stay fresh for up to a week – especially if you put a paper towel in the bag to absorb extra water.

Frequently Asked Questions

Q: What are onion sprouts good for?

A: Both onion microgreens and sprouts are full of nutrients. They can be added to green salads, sandwiches, casseroles, stir fry, and anything else that benefits from the flavor of onions.

Q: Which is healthier, sprouts or microgreens?

A: We’ll have to go with microgreens. They’re significantly larger than sprouts so you’ll get more nutrients, health benefits, and flavor from them (especially with onions!).

Q: Can microgreens make you sick?

A: As long as you follow the instructions well, your microgreens should be safe to eat. Getting sick from any home-grown food is typically due to pesticide spray or diseased plants.