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EmailBotanical name: Allium cepa
Plant type: Vegetable
USDA Hardiness Zones: 3, 4, 5, 6, 7, 8, 9
Soil pH: Neutral

Onions are a cold season crop, easy to grow because of their hardiness. We recommend using onion sets, which can be planted without worry of frost damage and have a higher success rate than direct seed or transplants. Onions are a basic and essential ingredient in many meals. We will focus on other onions such as garlic in another page. This page is specifically for yellow onions.
Planting
- Onion seeds are short-lived. If planting seeds indoors, start with fresh seeds each year.
- Till in aged manure or fertilizer the fall before planting.
- Start seeds indoors about 6 weeks before transplanting. Move transplants into the garden as soon as the ground can be worked.
- Plant the transplants about three inches apart.
- Plant sets directly outdoors 4 weeks before last spring frost. Make sure temperature doesn’t go below 20 degrees F.
- Think of onions as a leaf crop, not a root crop. When planting onion sets, don’t bury them completely under the soil; if more than the bottom third of the bulb is underground, growth can be restricted. Set five inches apart.
- Practice crop rotation.
Care
- Fertilize when bulbs begin to swell, and again when plants are one foot tall
- Generally, onions do not need consistent watering if mulch is used. If you want sweeter onions, water more.
- Onions will look healthy even if they are bone dry, be sure to water during drought conditions.
- Make sure soil is well-drained. Mulch will help retain moisture and stifle weeds.
- Cut or pull any onions that send up flower stalks.
Pests
- To control thrips—tiny insects about as fat as a sewing needle—take a dark piece of paper into the garden and knock the onion tops against it; if thrips are present, you will spot their tan-colored bodies on the paper. A couple of treatments with insecticidal soap kills them. Follow the package directions. Spray the plants twice, three days apart, and the thrips should disappear.
- Onion Maggots: Cover your emerging onion crop with a fine mesh netting. Seal it by mounding soil around the edges. The onion maggot likes to lay its eggs at the base of plants, so the netting should prevent that. You should also keep mulch away because the insects like decaying organic matter, and make sure you completely harvest your onions as the season progresses. Onion maggots are usually a problem in very rainy periods, so these precautions may be unnecessary if you have a dry season.
Harvest/Storage
- When onions start to mature, the tops become yellow and begin to fall over. At that point, bend the tops down or even stomp on them to speed the final ripening process.
- Loosen the soil to encourage drying, and after a few days turn them up and let them cure on dry ground. Always handle them very carefully—the slightest bruise will encourage rot to set in.
- When tops are brown, pull the onions.
- Be sure to harvest in late summer, before cool weather. Mature onions may spoil in fall weather.
- Allow onions to dry for several weeks before you store them in a root cellar or any other storage area. Spread them out on an open screen off the ground to dry.
- Store at 40 to 50 degrees F (4 to 10 degrees C) in braids or with the stems broken off.
- Mature, dry-skinned bulbs like it cool and dry, so don't store them with apples or potatoes.
Recommended Varieties
Onion varieties are classified into two categories: Long-day, best in the North, and short-day, best for the South.
- ‘Yellow Sweet Spanish’ long-day hybrid, large round shape, yellow-white.
- ‘Stuttgarter’ short-day variety sold in sets, early maturity with slightly flat shape, yellow.
Recipes
Wit & Wisdom
Onion's skin very thin,
Mild winter coming in;
Onion's skin thick and rough,
Coming winter cold and rough.
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Comments
When to harvest planting from sets?
Hi. I planted onion sets in Oct 2012. I live between Baltimore and Wilmington, DE. I also planted another round of sets in April 2013. When do you think I can stomp the greens and harvest? Thank you.
How long from bulb to ready
How long from bulb to ready to pick
Regular onions
I cant figure out when you harvest the regular onions. I dont think they really have a color and the stems on mine are tall but I don't know if the bulbs are mature enough.
wild green onions
I have wild green onions growing between the rocks in my ditch. theyre about 3ft tall. are they good to eat?
wild green onions growing in ditch 3 ft tall
This is a cattail! not a green onion, You can eat the roots.
planting onions from the grocery after they began growing.
I have store bought onions that began growing. I would like to plant them and see what happens. What can I expect at harvest time? Will I have more onions or just bulbs that grew, flowered and seeded?
You will not get an edible
You will not get an edible onion out of this, but you will get onion seeds (and green onion cuttings, I suppose).
Tiny white bugs destroying bulb. Not maggots...
A week ago I noticed my onions weren't doing so great.. My mother suggested digging one out to see what was going on. I did. They were loaded with reddish brown ants carrying around these tiny white things on their heads! I assumed they were ant larvae or something. So, I put some organic ant killer down and waited a week. I dug up another one and they are still looking sickly as ever, but now, if you peel back the first layer there is a multitude of these teeny tiny crawling white bugs! I also spotted one crystal clear super thin, like 1/2 the size of a sewing needle, worm?? Help!!! I'm pretty sure they aren't maggots. They have legs.
It sounds like you have onion
It sounds like you have onion maggots. The adult onion maggot fly lays it's eggs in the soil around onion plants in the spring and the maggots appear when the soil warms up. Yellow sticky traps will capture the flies in the early spring or you can use row covers to protect the onions. Plant a new row of onions in a different spot of your garden. Try red onions which are more resistant.
hail storm
Had a freak hail storm here in Texas the other day. It trampled the green stalks. Will this "speed up the ripening process" like if you stomped them? They still needed another 25 days or so to mature.
bent onion leaves
Garden lore tells us that bending the green leaves of onions close to maturity will help the plant to spend more energy on bulb growth. Unfortunately, this is not the case. The plant needs the leaves in working order so that they can make food for bulb growth. Bending or otherwise damaging the green leaves (such as via storm damage) will harm the growth of the bulb.
Because of hail damage, it is possible that your bulbs will be smaller this year. Harvest time might actually be delayed, depending on the percentage of leaves lost on each plant and the ability of the plant to recover. Some leaves might heal and help with bulb growth, or new leaves start to form, so we'd recommend leaving the plants alone in case they will perk up again. Wait until the leaves have yellowed and browned on their own before harvesting the bulbs.
onion blooms
my 1015 onions tops are about 10" and are setting blooms. A onion bulb has only begun to form. I planted them 62 days ago.
Is this normal?
onion flowers
Flowers on onions are not desirable (unless saving seed), as it compromises the quality of the bulb. Flowers can be triggered by temperature fluctuations (such as a period of warmth, followed by cold, followed by warmth).
A bulb uses energy to send up a flower stalk (called bolting), so once it does, the bulb will be smaller and won't be as large as an onion that does not bolt. It is still edible, but lower in quality. It is not necessary to cut off the flower stalks (some gardeners do, some don't), but you should harvest the bulb as soon as you can, and use it promptly--it will not store well.
When buying onion sets, look for those that are no thicker than a pencil, and plant them out at a time recommended for your area; larger sets tend to bolt. Also, keep in mind that 1015 onions are a short-day variety; make sure that type is recommended for your area. Short-day varieties form bulbs when daylength is between 10 and 12 hours; intermediate-day (day-neutral) onions start to form bulbs between about 12 and 14 hours of daylight; and long-day varieties form bulbs at about 14 to 16 hours daylight. If a short-day variety is planted in an area best suited for a long-day type, for example, then the bulbs might form early and not get very large. A general rule of thumb for the U.S. is that northern gardeners use a long-day type, gardeners in the mid-section use day-neutral, and southern gardeners, a short-day type.
no bulb
I live is San Diego county. I've planted several onion sets this past fall. None of them have actually formed a bulb. They're almost straight up and down. What am I doing wrong?
Onions come in
Onions come in long-daylength, medium-daylength, and short-daylength varieties, based on amount of sunlight needed. You grow long-daylength in northern latitudes and medium-daylength in central latitudes. In the southern latitudes, you need to plant short-day onions. Short-day do not come in sets. You need to seed OR plant bareroot transplants from local nurseries.
Fertilizer
Is 10-10-10 fertilizer just as good as 6-12-12 ? Thanks
For home garden use, either
For home garden use, either usually type usually meets the plant's requirements. Leafy veggies usually do better with a complete balance, and tuber/root veggies as well as flowers usually do better with 6:12:12.
fertilizer
What kind of fertilizer i need to spray to make the onion good? Thanks
Fertilizing onions is
Fertilizing onions is critical to success. Before planting, work 4 to 6 inches of well-composted organic matter and an all-purpose fertilizer (16-16-8) into the soil to a depth of 6-8 inches. Then, 4 to 6 weeks later, sidedress onions with nitrogen fertilizer (21-0-0) as directed. Do not
fertilize after mid-July as extra nutrients stimulate late season growth and reduce storage potential of dry onions.
Onions
I bought a bundle of white onion bulbs. I can not plant for 5-6 weeks. How do I store them sothey do not dry out and die.
Store sets (the tiny immature
Store sets (the tiny immature bulbs) in a cool, dry, dark environment if planting must be delayed after purchase.
leaf crop or root crop
It says to consider onions a leaf crop, not a root crop. Does that mean that I should plant onions in a waning moon?
Onions are considered a
Onions are considered a belowground crop. Plant during the dark, or waning, of the Moon: from the day after it is full to the day before it is new again.
sweet onions in Mississippi
I am about to set Georgia sweets and purple sweets. how far apart do i set them?
Georgia Sweet onions are
Georgia Sweet onions are planted 6 inches apart in rows 12 inches apart for full sized bulbs.
when to plant?
Bit old of a post but I'm still going to try. I would like to plant onions but I'm a little confused. I'm in zone 7 on north Carolina...when do I plant? Fall or spring? It says don't let temps go below 20..so if I plant them in fall the temps do sometimes go unto the teens in the winter. But summer seems to hot its been getting over 100 and that seems to hot for them so I'm not sure when to plant them. Any suggestions?
Planting dates in North
Planting dates in North Carolina for onions SEED are: Jan 15-Mar 31; Sept 1-30. Date for onion PLANTS or SETS are: Feb 1- Mar 15; Sept 1-15. Gardeners in plant hardiness Zone 7 and south will succeed best with short-day onion varieties.
Onion harvest
ok, so I'm supposed to stomp on the onions to speed the final ripening process, and in the next paragraph I'm supposed to "handle them very carefully, as the slightest bruise will cause rot" Would you please explain this????
Onion Harvest
They mean to stomp on the green tops after you have bent them over but be careful not to tramp on the onions themselves as they will bruise.
Yes, you stomp on the onion
Yes, you stomp on the onion tops, not the onions in the ground.
Harvest time
How many days are typical until harvest time?
Days to maturity for most
Days to maturity for most onions are: 100 to 120 (Mature bulbs)
Green Onions (scallions)
Plant sets deep for green onions? (scallions)
Set 1 to 2 inches apart and 1
Set 1 to 2 inches apart and 1 to 2 inches deep in the row.
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