Grow amazing alliums and learn how to plant onion bulbs at home. Starting onions from seed is easy; learn how to plant onion seeds and the best cultivars based on your growing zone.
Our family loves cooking with onions, so we decided to try growing our own a few years ago. We purchased onion starts online and had success, but after reading about starting our own seeds, we had to try them. From there, we’ve progressed to growing more varieties, larger onions, and more significant amounts. This year, we grew about 1,000 onions that we started ourselves!
First, take heart if you’re a beginner; onions aren’t an overly tricky crop to grow. They require lots of nitrogen-rich soil and consistent water and sunshine. Our area has few onion pests, and what we do have does minimal damage. However, each location is unique, so check with other onion growers in your area for pest specifics.
Onions can be grown in high tunnels, gardens, raised beds, and containers. Build hills to plant the onions directly into the ground. If you’re planting in raised beds, this isn’t necessary. To help retain moisture and prevent weeds, add mulch, such as straw, pine needles, chopped leaves, and strips of cardboard in the middle of the rows (don’t place cardboard too close to the onions, or they may not bulb effectively).
Many varieties of onions are broken down into three categories: short-day, intermediate, and long-day. Look at a map for onions to find your general area. Long-day onions are grown in the northern half of the U.S. and require about 15 hours of sun and are ready to harvest in about 90 days; intermediate onions are grown roughly in the middle of the U.S. and require about 12 hours of sun and are ready for harvest in about 110 days; and short-day onions are grown in southern states with about 10 hours of sun and are ready to harvest in about 110 days. If you live in another country, check your onion zone!
Some onions are better suited to certain climates, such as “cool and mountainous,” so if you live in a hot, humid climate like we do, don’t grow these and expect good results.
Starting Onions from Seed
You can buy starts or start your own from seed. As with anything, starting from seed provides a greater variety of choices than buying starts does. In our Zone, we need to start onions on the first of January. If you live in a southern Zone, you may often start seeds in summer, plant in the fall, and harvest in spring. We tried this and got a minimal harvest. After research, we realized that to do this successfully, we’d need to plant short-day varieties, not intermediate varieties.
To start onion seeds, place moistened seed-starting soil into containers with drain holes. Gently pack. Sow seeds in rows or just broadcast them in the containers. Unlike many crops, you can seed onions close together. Cover with seed-starting soil and lightly spray with water to moisten (not soak) the top. Place the containers into plastic bags, put a lid on them, or keep the soil sprayed daily until the seeds sprout. In our experience, onions sprout much quicker in a warm room. We start ours on a stand near our woodstove. After the seeds sprout, remove any lids or coverings and place about 2 inches below full-spectrum growing lights.
How to Plant Onion Seeds
There are two schools of thought on pruning your onion tops. One says to do it when they reach 4 inches and then continue to prune until you set them into the garden. The other says never to prune them, and you’ll get bigger bulbs. We’ve done both and, quite honestly, achieved good results with both. One advantage of pruning is that you won’t need to keep moving your lights up as they grow, and you can also eat the prunings! Make sure your onions don’t dry out, but also don’t waterlog them. Fertilize with a weak natural fertilizer weekly (we use a fish-seaweed emulsion at 1/4 strength).
How to Plant Onion Bulbs
Onions should be planted as early as possible. In my area, this is March (if we had a high tunnel, we could plant in February) for a harvest in late June. The longer the onions have to grow before it gets too hot, the better they’ll be! Onions are incredibly hardy and can withstand frost and even some freezes. Gently separate the roots in your containers and plant your onions with all the tops out of the ground and the roots barely in; don’t bury them deeper! Plant 6 inches apart in rows and place the rows 6 to 9 inches apart – then water well. Onions require a lot of nitrogen for proper growth, so make sure your soil is nitrogen-rich. Either fertilize with a pelletized natural fertilizer with a high nitrogen content, or side-dress with aged chicken, rabbit, or goat manure.
As your onions grow, fertilize every two weeks. We dig furrows beside each row and bury the fertilizer. We also spray ours with a mixture called “Chicken Soup for the Soil” and a fish-seaweed emulsion. Keep onions watered; they may require daily watering during dry weather. Weeding is essential for onions, as they intensely dislike competing with weeds. In our experience, loose soils and full sun make the biggest onions.
Onion tops will eventually make your bulbs, so don’t clip the tops once you plant them in your garden. Keep an eye out for pests and treat them promptly. We use a few natural pesticides in our garden: Bacillus thuringiensis (Bt), diatomaceous earth, neem, and spinosad. Hand-picking pests is often effective for minimal problems.
Once your onions start bulbing (where the bottom or root swells), stop fertilizing but continue to water well. Some people recommend loosening the dirt around the bulbs as they grow, but this isn’t necessary, as the bulbs will naturally push back the soil.
Harvesting
You’ll know your onions are about ready for harvest when the tops start falling over. Stop watering at this point. After 50 percent of the onions have fallen over, bend the rest over. Pull the onions when the outer tops have browned. Grasp the onions at the bottom of the stem and firmly tug upward. If the stem is too dry, it’ll most likely break off, so pulling them before they get too browned is best. Brush off any dirt, don’t remove the skin layer on the outside of the onions, and leave the tops on.
Storing Options
You’ll need to let your onions sit in a breathable area for several weeks to cure them for long-term storage. There are several different options for this. We take a long board and nail heavy nails partway into it every 6 inches. Then, we take a handful of onions, bind them together with twine, and then hang the bundle on the nail. The size and weight of the onions determine how many are in each bundle. We generally put 8 to 12 onions together. This board is fastened under a protected side of a shed where they get air but no rain. Another method that works well but requires more room is a series of screened frames where you can lay the onions out flat (side by side, not on top of each other). Still others cure theirs in the garden, but only do this if you have dry weather!
Once the tops have dried or the stem right above the bulb is dried, cut them off about 1 to 2 inches above the bulb, place them in netted bags, and store them in a cool, dry place. Different cultivars have different storage times, so keep a close eye on them. We store ours in netted bags under the house hanging from nails on the floor rafters. Any bulbs that are tiny or damaged should be used or preserved promptly. A few options for preserving are chopping and freezing, dehydrating, and pickling.
Onion Seeds and Cultivars
There are a multitude of wonderful onion varieties and many suppliers. We bought our seeds from Southern Exposure Seed Exchange and were more than pleased with the quality. They sprouted well, and we had an excellent crop. The cultivars we tried this year were ‘Walla Walla,’ ‘Red Wethersfield,’ and ‘Texas Super-Sweet’ (a hybrid from another company).
Of those three, our favorite was ‘Walla Walla.’ They were a big, beautiful, sweet yellow onion. The ‘Red Wethersfield’ grew well but weren’t as large and turned out quite spicy. The ‘Texas Super-Sweet,’ a short-day cultivar, was our least favorite because the onions didn’t grow as large (but were delicious), and in hindsight, I think we were just too far north for their preferred climate. Remember to read the description of each onion cultivar before you purchase!
Here are some cultivars I recommend:
Short-day:
- ‘Texas Early Grano’
- ‘Texas Super-Sweet’
- ‘Red Creole’
Intermediate:
- ‘Candy’
- ‘Red Candy Apple’
- ‘Walla Walla’
Long-day:
- Red ‘Wethersfield’
- ‘Rossa di Milano’
- ‘Yellow Sweet Spanish Utah’
Growing onions is a great way to become more sustainable on your homestead or farm. I encourage you to try it and see if those homegrown onions aren’t a flavorful, healthy addition to your meals!
Resources:
- Annie’s Heirloom Seeds
- Baker Creek Heirloom Seeds
- Berlin Seeds
- Brown’s Omaha Plant Farms
- Burrell Seed Growers
- Dixondale Farms
- Fedco Seeds
- Filaree Farm
- Harris Seeds
- Irish Eyes
- Johnny’s Selected Seeds
- J.W. Jung Seed Company
- Keene Garlic
- Meadowlark Hearth
- New England Seed
- Seed Savers Exchange
- Southern Exposure Seed Exchange
- Territorial Seed Company
- Turtle Tree Seed
Originally published as “Amazing Alliums” in the December 2024/January 2025 issue of MOTHER EARTH NEWS magazine and regularly vetted for accuracy.
Jenny Underwood is a homeschooling mom to four blessings. She lives on a fifth-generation homestead with her husband of 24 years. You’ll often find her in the garden or curled up with a good book and a great cup of coffee.
