When the onion is a bulb, not a seedling or a sprout, it can take anywhere from 8 to 12 weeks from the time you plant it until it’s ready to harvest.
Sometimes earlier depending on variety and temperature.
Onions (Allium cepa) produce bulbs and grow from small plants to medium-sized plants in a single growing season.
If the weather is right, onions will establish their bulbous roots within one month of planting outdoors.
Bulbing may take up to four months or longer for specific varieties before they mature and are ready to harvest, leaving the onion root intact for replanting.
Determinate varieties such as ‘Danvers 126’ produce their flowers and develop underground bulbs all at once, maturing within 60 days after planting. This process can be observed belowground with a hint of green showing through the soil.
Onions that offer an endless production possibility keep growing and producing more leaves and stems than flowers and developing more bulbs. Onions that are indeterminate, such as ‘Copra’, will continue to grow into an enormous plants.
Onions form bulbs when the day length decreases below 16 hours and increases above eight hours. Onion bulbs will not form if planted in areas where summer temperatures do not remain between 18-20 degrees Celsius (64-68 degrees Fahrenheit).
Onions require periods of cool weather before their growth stage can begin: They must be planted four to six weeks before the final frost-free date for your area occurs, and planting should take place after all danger of frost has passed.
The amount of time it takes for onions to mature depends on the variety you choose to plant. Some varieties, such as ‘Yellow Globe’ and ‘White Bermuda’, are ready for harvest after growing to a height of between three and six inches.
Some growers have reported that the number of days it takes onions to grow depends on weather conditions during the summer months, including temperature, humidity, rainfall amounts, and sunshine hours.
However, the length of time that it takes onions to grow does not seem dependent upon these factors when compared with other agricultural products grown in similar environmental conditions.
For example, potatoes are able to be harvested around 100 days after planting, while onions will provide you with your first batch of green onions in 100-120 days.
‘Thumbelina’ type carrots take 110 days until they are mature enough for harvesting. It is possible for green onion growth to take two weeks longer than what is estimated above if your weather is especially hot.
| Family | Amaryllidaceae |
| Genus | Allium |
| Kingdom | Plantae |
| Order | Asparagales |
Steps to Growing Onions
Establish when you want to harvest your crop. Onions are ready for harvesting when the green tops begin to fall over and dieback (120 days). Although this will happen at some point, onions are usually harvested before this occurs.
This stage varies depending on the variety of onions that you have planted. Some varieties, such as ‘Roselawn’ cultivars, will produce their first blooms after 90-100 days. For other varieties, it may take up to 120 days or longer until bulbs are ready for harvesting.
Afternoon sunshine seems to cause onions to bolt more quickly than morning sunshine, so it is best not to water in the afternoon hours.
Root your chosen variety of onions by digging holes in the ground about 4-6 inches deep and place 2-3 onions per hole approximately 10 inches apart.
They should be placed with their roots pointing down into the soil, although the top of each bulb should be at or just below the soil surface. One plant can produce up to 5-7 bulbs, depending on the variety you have chosen.
If you are planting sets, they should be planted three t four sets per hole. It is important not to plant too many seedlings together as this may lead to small onions forming before the summer weather has had time to develop its full effect on growth.
This will result in smaller-sized products for you if you follow this step. Allow enough space between plants for them to grow and receive sunlight.
How do I know when my onions are ready to harvest?
In the fall, you can harvest your onions from late September through November. It is best to leave them in the ground for as long as possible.
When harvesting onions, bring a spade or fork with you and be very careful not to damage other plants or bulbs around them. To harvest an onion bulb, angle the blade of a spade under the side of the bulb and lift it clear. Do this for a number of plants until you have harvested all of your crops.
If there are green shoots coming up from the center of the onion then they will continue to grow into new plants. You must remove these shoots if you want to allow those that have been harvested to replenish themselves.
Generally speaking, an onion is ready to harvest when it has weakened and died back, its top growth has collapsed and the onion skin feels dry. The skin of the onion should be brown, paper-like in texture, and not at all green underneath.
Keep an eye on your onions until they are ready for collection – sometimes they can feel like they are dying back but the foliage recovers leaving you wondering if they were ever really ready.
Making use of some or all of your harvested onions: Before storing your harvested onions it is essential that any dirt is removed from them. To do this just rub off any loose soil with your gloved hands. Remember to never pull off the outer layer as this will damage the bulb beneath!
Now for storage. Onions must be stored in a cool, dark place with good air circulation. Onions generally keep best between 32 and 40 degrees Fahrenheit.
To prepare harvested onions for storage simply cut the foliage about one inch above the bulb and then remove any loose dirt.
If you have too much onion to store it can be hung from strings or braided together. Be sure that they are kept in the coolest part of your house – even through winter they will keep quite happily.
How Long Do You Cure Onions?
Curing, also known as pickling or fermenting, is a method of preserving food by either lactofermentation or salting where vegetables are submerged in the brine.
The main difference between Lacto-fermenting and salting is that with Lacto-fermentation the goal isn’t to achieve a specific amount of saltiness, but rather a specific flavor profile.
With fermentation, you control how much salt is present by limiting the amount of salt going into the brine so it doesn’t overpower the flavor.
Salt is used for both fermenting and salting because it draws liquid out of vegetables over time, creating brine, which creates an environment where enough friendly bacteria can grow to safely preserve the vegetables without the need for refrigeration.
The goal of curing is usually to infuse foods with salt or other seasonings that enhance or change flavors.
Curing onions will change their texture and flavor by drawing out moisture through osmosis, this also changes their density. When you cure onions they’re usually placed in a warm place so heat can speed up the process. Curing usually takes about 5 days but depends on what your goals are as well as how long you let them sit for each day.
Remember, you don’t have to cure onions, especially if you’re only using them in a recipe that calls for finely chopped fresh onions.
How Many Days to Cure Onions?
You can cure onions in a few different ways. The easiest way is to leave them in a cool dry place for 10 days. It’s recommended you slice the onions before curing them, but this isn’t necessary. Most sources say 3 – 5 days minimum without slicing, and others say the sliced method takes 1-2 days longer than not slicing.
Sliced Onions: Put your sliced onions into a bowl with 2 tablespoons of salt per 5 pounds of onion you’re using. Stir every day for 4 or 5 days until they turn somewhat translucent and limp-looking.
Then put them in a covered container in a cool dry place for another 10 days or so (the time it takes to see some color on new sprouts). At that point, they should be done, but you can also dry them artificially (see below) if you want.
Unsliced Onions: Put your unsliced onions into a bowl with 2 tablespoons of salt per 5 pounds of onion you’re using. Stir every day for 10 days or so (the time it takes to see some color on new sprouts). At that point, they should be done, but you can also dry them artificially if you want.
Artificial Drying: If the natural drying process is too slow for your schedule, artificial drying works just as well and only takes about 3 days – faster than leaving them in a cool dark place until cured.
Artificial drying is accomplished by heating the air around the batches of onions to dry them out. Doing this is a two-step process requiring the use of fans and dehumidifiers, which can be purchased at any major home improvement store.
Here’s what you need:
- Drying Chamber (airtight) about 4 feet wide and 10-12 feet long with one wall open or screen on one side for airflow
- A large fan with adjustable speed settings
- A dehumidifier
Here’s how it works: Set up your drying chamber so that the cooling device is on one end and the fan is on the other end, both facing into the drying chamber. Put your unsliced onions in baskets or just lay them directly on top of that screen or open wall so they’re not touching each other.
Turn the cooling device on and set it to 65°F and 65% humidity. Set the fan on low and put it about a foot away from the wall with the screen or open space facing into the drying chamber (the screen is there so you can’t see through to what’s behind it, but air can still flow through).
Place your dehumidifier outside of your drying chamber (on the same end as the cooling unit) and make sure it’s close enough to pull air in from its intake vent. Then adjust all settings as needed for max efficiency: turning up both devices will save time; turning down either one will slow things down.
You want a temperature setting as close to 55°F as possible without going below that, and you want the humidity as close to 50% as possible without going under that. That will ensure your onions dry out perfectly with no mold or bacterial growth.
After 3 days, turn the cooling unit off but keep the fan running for another 24 hours or so to ensure everything is fully dried out. Then just take them inside, let them rest in front of a fan for a day to get the bends out, and store them any way you like.
Cured Onions: Put your cured onions into Mason jars using this guide. Then leave them on your counter for 2 weeks before transferring them to cold storage.
How Many Onions Will One Onion Grow?
An onion will grow a new onion. An onion cannot be divided into a smaller number of onions that is, an onion can only have one layer or peel removed from it before being destroyed/dead.
Each onion is connected to another bulb through its root system and therefore it would be impossible for one single onion to produce the number of onions required in order for them all to survive. This means that they need each other to live and reproduce.
An onion will grow another onion from itself. There appears to be no limit on how many layers an onion may grow in the future, but there is a limit on how much each individual can grow in height/length/width in any given year which produces this kind of exponential growth with the number of onions grown.
Conclusion
Onions can be grown from seed or setts, and both take different lengths of time to mature and produce a crop.
Onions require a long growing season (from 90 days to 180 days) and should not be planted until the soil has warmed up in spring.
Once they reach the bulb-producing stage, onions need between three months and six months before they can be harvested, depending on the type.