How Long Do Onion Sets Last
Onion sets can last for up to 3 weeks or a month if they are stored in a cool, dry, and dark place like a cool pantry or basement such in a place with no direct sunlight. To keep the onion sets healthy, follow the rules to store them properly.
Onions sets are typically grown during onion planting season, and therefore, you will need to keep them appropriately stored until the planting season. To maintain onion sets health, always practice good storage practices to ensure they can thrive well when the season comes, which is from March through April. The later-growing onion sets will more easily bud left in a greenhouse, and they are far away from birds, which could otherwise knock them from the ground, should you be planting directly in a garden bed outside.
Planting second-season onion sets produces a first-ever crop of onion bulbs in long-season regions – far before the first-ever harvest, and in short-season regions, onion sets yield larger onions than would naturally occur. In the long-day regions, they can grow to full size, but are susceptible to ibolti, meaning that they produce seed pods. If planted in a short day or midday region, onions that are established will produce green onions, as they never get sufficient daylight hours to initiate the process of bulbing.
You can plant onions nearly anytime of year (especially if growing green onions), but the time you choose to grow them will affect how big of onions you will get and when you will harvest them. In addition to deciding whether you need longer-day onions versus shorter-day onions, and then making a decision about seeds, sets, or transplants, now you will have to decide what type of onions you want to grow. A big part of this has to do with how you keep your onion plants, but also a critical component is what type of onions you are growing. Fortunately, you have plenty of options to choose from when choosing the best onions for storage.
Keep in mind that when choosing the best onions for storing, there are a number of different varieties of onions that the seed companies carry. Generally, there are only two or three onion varieties that are typically available in sets, but there are dozens upon dozens of onion varieties that are available in seeds and are more likely to perform well in your garden. Onion sets are easily found in garden centers, big-box stores, and even in the produce section of your supermarket, but just because they are easier to find does not make them the best onions to grow.
I love growing onions from sets, as they are easier than having to fumble around trying to germinate seeds in a frozen winter, and I can generally get sets for cheap if I wait until late spring (or get them from Poundland). A set that is around 3/4-inch (2-centimeter) diameter is perfect; this will produce spring onions rapidly if planted the following season; left in the ground through the late summer, this will produce nice-sized bulbs. Plant sets 1-to-1 1/2 inches deep and 2-to-3 inches apart for growing bulb onions; sets grown for green onions may be planted closer together. Try planting seed onions rather than sets this year, and you will have a productive crop of these fine bulbs.
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Onion seeds should be planted early in spring, when temperatures are cool, and they will follow a traditional, 2-year lifecycle, starting with seed, then blooming in the following season. This means that seeds need to be started several weeks before moving plants outdoors to a garden. Because of this lengthy growing season requirement, and onions preference for cool weather, planting onions seeds straight into the garden in spring makes it hard to get the bulbs to reach good size before warmer temperatures arrive. If you plant your onion seeds indoors under a grow light and keep the lights on that long, this triggers early bulb sets and results in smaller onions.
| Facts | |
| When Should Be Planted | In a cool temperature and several weeks before moving plants outdoors to a garden. |
| Traditional Life Cycle | 2 years |
What this means is even if your greenhouse stays at a warm 80F throughout the winter, you cannot grow onion bulbs there unless you add grow lights to get to similar amounts of daylight hours as in summer. To produce the correct bulbs, onions require a specific number of hours of daylight during a growing season.
Your goal is to have as many leaves growing on an onion plant as possible before your areas signal for forming bulbs begins. By mid-summer, when bulbs begin fattening, you can begin picking individual onions if needed. Starting means that you can start planting your onion sets as late as May 18th and still have 100 days of optimal onion bulbing. We recommend planting onions that are started (replanted) or planted into soil a month or so before the last freeze to be planted for the spring.
If it is a dry weather year with no risk of frost, you can pull your onion plants out gently from the ground and leave them in their gardens for one to two days. Growful Pro Tip We prefer direct planting for winter, but for planting onion sets or transplants for winter, start them 4-6 weeks before the first fall freeze. This humidity can come from rainfall and soil moisture, easily, but if you would like to speed up the process, you can soak the onion sets overnight in compost tea or non-chlorinated water prior to planting.
Onions do not need much extra watering, unless you are experiencing extended periods of drought. In July, you should add some extra water to onions, as onions will store up and use that water during the fall and winter. This will prolong the lifespan of your garden onions, and will enable you to continue using your own garden grown onions, until hopefully, you get some young, green, tender onions that you can harvest from your own garden.
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Enjoy eating the harvest from the garden through the winter months, knowing what varieties are best to save onions. Choose vegetable and onion varieties according to how much light is available in the growing seasons you have at the height. Sweet onions are not very good for storage because of their sugar content, so I concentrate on planting my own storage onions from seed or saving them, while I grab a bag of Walla Wallas from my local nursery if I am not planting some myself from seed.
You can buy transplant onions at Topeka, Kansas Plant Nursery, and grow them in a garden in your house, producing larger bulbs than what you will get from sets. I just purchased six gallon buckets of red onion bulbs for planting, as a plant store was getting rid of them for 50c//gallon. At an allotment, you have undoubtedly seen people planting onions at the end of March or the beginning to middle of April (which is a recommended timing), but if you wanted to continue to grow them, I never had any problems with them being planted at mid-May (I have just been transplanting a few over the weekend).
How do you know if onion sets are still good?
Regularly inspect the onion sets in the bag for any decay or damage. Remove any sets you notice starting to decay from the bag immediately since they might spread the rot to the remaining sets. It is advised to keep the onion sets in a cool, dry, and dark place such as a basement or cool pantry for up to three weeks
How do you overwinter onion sets?
As they grow underground, onions can withstand freezing temperatures. In colder northern areas, a covering of mulch is beneficial for overwintering onions. Winter onions can also be cultivated in containers. Harvest the onions and store them in the container next to the kitchen door so you may utilize them all winter.
How deep do I plant onion sets?
The plant starts to grow in the early spring as soon as the ground can support it. Sets need to be planted at a depth of 1 to 1 1/2 inches, in rows that are 12 to 15 inches apart. For dry onions, space the sets 2 to 3 inches apart. You can grow green onion sets closer together.