Onions, they might make us cry occasionally, but we can all agree that without onions, we’d be crying even more, and here’s how to grow your own bulbous onions from home for that almost never ending supply of deliciousness!
Climate for growing onions
Onions are as hardy as they come and are regarded as a cool season plant but will grow well in a wide range of temperatures.
Even young plants don’t mind frosts or snow; although -5°C (21°F) temperatures for months on end will more than slow their growth… it will kill exposed onion plants.
The best temperatures for growing onions are from 13-25°C (55-75°F). They produce higher quality bulbs if the weather is cool during their early growth stage, then they like increased temperatures for optimum maturity.
When in full growth, onions like 6 hours or more sunlight most days.
The cultivation of onions is very interesting due to the technicalities involved. The bulb of the onion is formed of fleshy and enlarged leaf bases or scales. The hollow green leaves develop in a sequence from the meristem, which is the innermost portion of the base of the bulb.
Sow or plant onions to avoid frost so that they grow without any setbacks. Planting onions is best done when the last frost in your area has (hopefully) been sent packing by spring.
Growing onions over summer means you will harvest as summer closes. In mild and warm areas you can plant onions in late summer and autumn/fall for a spring harvest.
Choosing different types when growing onions, determines when to plant them. The bulbs start to form once a certain number of daylight hours are reached. The different day-length sensitive types are:
• The traditional garden onion is referred to as “long-day” and needs at least 15 hours of daylight with good sun. The long day onion varieties are best grown in colder growing areas.
• There are “intermediate-day” onion types needing only 12-13 good daylight hours to stimulate the formation of bulbs.
• More recently “short-day” onions are happy to form bulbs after 9 hours of bright daylight. These types are good for hotter growing areas with mild winters and can be planted in late summer and harvested the following spring.
Growing onions — seeds, seedlings and sets
When it comes to choices we tend to go with the easiest, but with gardening it often proves better to put in a bit more effort up front to get superior results.
You can buy a packet of onion seeds and sprinkle them down a few rows, thin out the seedlings and eat as green shoots, then let the rest bulb up and hey presto — nice, fat onions about 5 months later.
Or, a little more work, but speeding up the process, you can buy seedlings which are sometimes called onion transplants, and plant them carefully, or…
Buy onion ‘sets’ which are small onions, and you plant each bulb nicely spaced from each other. Of course this method is the hardest, most expensive but produces onions the fastest.
Planting onions with seeds is easy once the groundwork is done;
Inside: Planting the seedlings into seed trays, in a hothouse, sunny windowsill or a heat lamp/ pad will give you a 2 month head start on nature, just make sure to keep them damp. Exposing them to outside weather will harden them, getting them ready for life outside, just watch out for frost!
Outside: It takes about 2 weeks for the seeds to germinate when the temperature of the soil is 10 degrees Celsius. They need to be sowed at around 2.5cm deep with the same distance between each seed, and at least 50cm space between the rows.
It’s best to wait until the shoots are pencil thickness, and before they bulb, before you start picking out the ones you want to use, but bare in mind, that depending on the variety of onion, you’ll need at least 7.5cm spacing (for the average garden onion), 2.5cm spacing for the pearl onion and for the really large ones, up to 15cm is best.
Seedlings or transplants, what to choose…
The best onions are, of course, grown from seedlings, but make sure the frost has gone. Take good care of them and the only tears you’ll have, will be of joy throughout winter!
Growing onion sets.. game and match!
Sets are onions that were planted from seed last year, you can save them yourself, or you can buy them if yours were too irresistible to save.
However, if you’d like to learn how to make your own sets, then read on!
Planting them close together will limit growth on the bulb.. much like people in a crowded bus or train, these can be harvested and stored for the next years plantings.. the onions, not the people.
For a more in-depth explanation on the ins and outs of making your own sets, click the link below.. it’s a long read, but definitely worth it!
Soil preparation before growing onions
Onions have soft roots so dislike heavy soils. The soil has to be well drained, friable and fertile for growing onions. Soil pH should be 6-6.8.
Onions love lots of old manure and compost mixed in for several weeks before planting.
Because onions have slender leaves and don’t block much light, the surrounding space between each onion plant receives lots of sunshine which encourages weed growth and allows weed seeds to blow in and thrive.
Keep the area as weed free as possible and don’t disturb the onion roots when weeding.
Also don’t grow plants with aggressive roots nearby.
Nutrient requirements for best onion growing
When growing onions they need uniform moisture throughout the season, otherwise fully formed bulbs will not be produced.
If you have heavy soil and let it dry out, it could crack and damage the onion bulbs causing distortion.
Feed an organic fertiliser every 3-4 weeks during growing and bulbing stage.
Once the bulbs are mature, hold off any irrigation or feeding to allow the bulbs to dry and harden ready for use and storage.
As well as growing different onions for their yields and usage, there’s also a range of shapes and sizes. The bulbing or dry onion varieties can also be roughly categorised into spring/summer types and autumn/winter types.
- Red onion: A sweet, short storage onion, often eaten raw.
- Vidalia onions: A large, sweet and mild onion. Really a Yellow Granex variety, but onions grown in the low-sulphured soils of Vidalia US are particularly sweet and are allowed to be called Vidalia onions.
- Red pearl and White pearl onions: Small, sweet and great for pickling and boiling.
- Maui onion: A large, sweet and mild onion.
- Cipollini onion: A mid-sized, flat onion, good for cooking.
- Yellow/brown onions: The most common onion for cooking and great long storer.
- White onions: A popular cooking and storing onion, slightly milder than yellow onions.
- Egyptian walking onion: A weirdo but popular. Has underground bulbs which have a strong, unpleasant taste so only the clusters produced on the end of the stems are used. Often the tops bow over with the weight of the bulbs which take root in the soil to grow more onions, thus ‘walking’ over the garden.
Harvesting and storing onions
For long storage onions the onion tops should be manually broken over to speed up with drying the necks before harvesting. The back of a rake is a handy garden tool for doing this.Your growing onions are nice and fat and raised slightly out of the soil… then you notice the leaves starting to turn yellow and even some fall over. That’s a sign the onions are mature and almost ready to harvest.
Basically, by bending the leaves you’re stopping the leaves growing further by cutting off the flowing sap and instead diverting all the plant’s energy into the maturing bulb.
At least fifty percent of the tops must be broken over before harvesting storage onions. When growing onions for immediate consumption, they can be harvested with about 20% of the tops broken over.
It takes roughly one week after the tops are bent over before they have withered and turned brown enough so you can lift out your onions.
Here’s a bit of a run-down of the storage technical specifications:
Before storing onions, a process of curing needs to be undertaken. The precise purpose of curing is to ensure drying and dormancy.
Fully mature onions are cured by exposure to approximately 35°C, with less than 50% humidity. At curing stage, the air movement should be allowed at the rate of 1 cubic foot/minute/cubic foot of onions.
Immature onions necessitate twice the rate of air exchange. After curing, the temperature should be lowered to 0°C gradually. The relative humidity should be 60-70%.
To prevent condensation on the bulbs, air exchange is very important. When the bulbs are removed from storage, they should be conditioned for several days at 20-50% relative humidity.
Depending on the onion cultivar used, the freshly harvested onions remain dormant and do not sprout. At storage stage, sprouting occurs, when the storage temperature goes above 4.4°C, and recedes after the temperature exceeds 25°C.
Read the quite heavy article over at www.no-dig-vegetablegarden.com/growing-onions.html