When you have fresh green onions in your kitchen, the cooking possibilities from each harvest are endless. Used raw, the crisp stems add a robust garnish to salads and dips. Cooked, the stems can add a refreshing kick to omelets, casseroles, and baked potatoes. Now, your inner chef is wondering how to grow green onions indoors. We’ve researched the best growing methods for green onions to give you the answer.
- Select a planter (pot, window box, up-cycled egg carton, etc.), and fill with permeable soil.
- Plant onion seeds, bulb sets, or root scraps.
- Keep soil moist, and put the planter in a sunny location.
- Harvest stems at 6” tall.
Green onions grow heartily indoors all year-round as long as you provide the right conditions. These vegetables not only freshen-up recipes but will brighten your kitchen with a vibrant burst of color. Keep reading, and we’ll show you how to grow and care for green onions indoors by planting in either soil or water.
How To Plant Green Onions
Green onions (Allium cepa) are in fact just immature onions. You might also hear these onions referred to as scallions, spring onions, and bunch onions. The young plants produce lush, flavorful stems that can be harvested before the bulb is fully developed.
Grown indoors, green onions thrive throughout the year. These bunching onions produce firm, green stems and pure, white bulbs. The entire plant can be eaten, either raw or cooked.
Although there are several varieties of green onions, some of the most common bunching types include Evergreen Long White, Parade, and Lisbon. You can grow green onions from seeds, bulb sets, or leftover bare roots.
Seeds
Sow seeds by planting them 1/2” deep in permeable soil. If using one planter, sow seeds between 2” and 6” apart. Keep soil moist, and put the planter in a warm, sunny location. You should see sprouts emerge within 7 to 14 days.
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Bulb Sets
Onion sets are packaged bundles of small bulbs. You will typically find sets at garden centers during the spring, ready for seasonal planting. The bulbs come from various types of onions, having been harvested within the plant’s first year and kept dormant over winter.
To plant sets, just press the bulb into the soil leaving the top exposed. If using one planter or window box, keep the bulbs between 3 and 4 inches apart. You should see green shoots begin to emerge within 7 days.
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Bare Roots
Start with fresh, mature green onions and cut off the top green stem portion of the onion to leave only the white stem, bulb, and roots.
Plant the bulb and roots, by pressing the bulb deeply enough into the soil to completely cover the roots, and just leave the top of the bulb exposed. You should see green shoots begin to emerge within 5 days.
Green onions make a great addition to an indoor herb garden. Check out our post How to Make an Indoor Vertical Herb Garden to get ideas on how to maximize your indoor garden space.
How To Care For Green Onions Indoors?
Keep the soil moist by providing about 1” of water per week and watering 2 to 3 times per week. Green onions have shallow root systems, so it is important to avoid getting the top of the bulb (or stem base) too wet or the roots can rot.
Use permeable soil, and select a planter or pot that allows drainage at the bottom. Providing a balanced fertilizer can stimulate growth. Green onions prefer slightly acidic soil, with a pH of 6 or 7.
Put the planter in a warm, sunny location. Green onions prefer full sun and warm to cool temperatures between 55°F and 65°F.
Harvest Stems & Bulbs
You can harvest the green stems at 6” to 8” tall. Cut the stem for immediate use. Leave approximately 3” of the stem so the plant will stay healthy and continue to grow.
When the tops of the stems become yellowed (approximately 90 days after planting), the onion bulb has fully matured. Bend the stems down, and loosen the soil around the bulb. Allow the bulb to dry, remaining in the soil until the stem tops have browned. Pull the bulbs to either use immediately, or to store in a cool (40-50°F) dry location.
Do Green Onions Grow Better In Water or Soil?
Surprisingly, green onions actually grow more quickly in water than in soil. Check out this experiment to see the results captured on film.
You can grow green onions hydroponically by using a container as simplistic as a mason jar. Alternatively, you can add a hydroponic planter to your home so you can enjoy a bountiful onion harvest during any season.
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How Long Does It Take Green Onions To Grow Indoors?
When you germinate green onions from seeds, you can expect to see sprouts within 7 to 14 days after sowing. Successful sprouts will grow quickly, and the bulbs will fully mature within 14-weeks (100 days).
You can harvest the tops of green onions, or scallions, when the plants reach 6” tall. The plant will continue to grow and remain healthy as long as you leave 3” to 4” of top greenery between harvests.
How Do You Regrow Green Onions?
Regrowing green onions is an economical way to make sure you’ll never need to buy these tasty veggies again. Not only will you always have fresh green onions to add to your favorite recipes, but you will also reduce waste from your kitchen.
Follow these simple steps to regrow green onions in water:
- Cut off the top green portion of the onion and leave approximately 1” of the stem along with the white, bulb portion and roots.
- Place the bulb and roots into a translucent glass jar.
- Add water to the jar to submerge the root ends.
- Place the jar in a warm location that receives full sunlight.
- Watch the onions grow! Within 3 to 5 days green shoots will emerge. You can harvest the greenery at 6” to 8” tall.
Hydroponic green onions will thrive for about 4 or 5 harvests, and then the root system will begin to weaken. If you want to extend the life of your green onions, transplant the root system into soil. The soil will provide nutrients so the plant can continue to grow.
You can transplant green onions from water into soil when the stems reach between 6” and 8” tall. As the bulb matures, you can continue to harvest green stems. Harvest mature bulbs after between 90 to 100 days of planting, depending on the onion variety.
Do Green Onions Need Sun?
Green onions do prefer full sun. But, if you are growing green onions indoors, you can substitute sunlight by using a fluorescent plant light.
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Adjust the height of the fluorescent light to be approximately 5-inches above the plant. Do not leave the light on for 24-hours because plants need a rest period just like we do. Provide at least 12 to 16 hours of fluorescent light per day for optimal growth.
Now that you know how to plant and grow green onions indoors, you might want to add other types of vegetables to the mix. Check out our post Can You Grow Vegetables Indoors All Year Round?
I live in Zone 7 and so far my onions are doing well with hard freezes. They are in containers on my patio and receive a lot of direct sunlight in the morning. I harvested the tops when it first got cold, mulched the pot, and they have sprung right back to life. During the summer, I found that overwatering is a sure way to impair their growth, even when living in the high desert and temps at 100° for several days. As for pests, I’ve had no problems with thrips or aphids even though my potato plants right next to them did. I wish I had as much success with garlic which seems way more susceptible to overwatering. I’m happy to have a winter crop. The potato tops are gone now, killed by the freeze, but I know the potatoes themselves are thriving since I have grown them in a container in the past. Maybe winter gardening will become a new hobby for me since I don’t have to worry about thrips and aphids. For some reason, thrips have always been my biggest issue with tomatoes, potatoes, peppers, and herbs. The thrips also target weeds. Looking forward to seeing the results of my experimentation.