How to Grow Onions

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In this article we will talk about how to grow onions, whose scientific name is Allium cepa, being a plant that is grown biennially, however usually onion cultivation is done annually. The edible part of this plant is the bulbs, which can be consumed raw or prepared in a wide variety of dishes, the onion leaves can also be consumed when the plant is still young as a substitute for chives.

Onion is one of the most cultivated and most demanded vegetable in the world. After tomato is the second most important vegetable with about 84 million tons produced in the world per year. Onion is widely used in most gastronomic cultures and very beneficial for health because they contain a considerable amount of nutrients and is the reason why it is used for medicinal purposes. Humans can consume onions without any problem, however it’s very toxic for many mammals such as dogs and cats.

In addition, it’s a crop that has great genetic diversity adaptable to different agroclimatic conditions, being able to establish itself successfully in many regions. Each area has it’s own shape, which depends on the circumstances and the place where it’s planted, but all must meet a series of requirements for the good cultivation of onion. Today it’s possible to plant onion at home with the development of urban gardens and thus enjoy their natural benefits directly. Within the good agronomic management the sowing method is vital since it’s possible to provide the seed with the most favorable temperature, humidity and oxygenation conditions for it’s good development.

We can sow onions throughout the year. Onions are a type of root vegetable withstand low temperatures well, so we can prepare it’s crop practically all year if we live in a mild climate. Although as we said the onion endures low temperatures, it’s ideal to start growing during spring. Onions need light and require a place that receives a good number of hours of sunshine throughout the day. So it’s convenient to avoid sites that receive shade from tress, walls or other elements.

Select your variety

The choice of onion to sow is very important; Depending on the season and region, it can be varieties of short, intermediate or long days. We will choose onions of short days when there are conditions of 12 to 13 hours of light, intermediate with 13 to 14 hours of light and long with more than 14 hours of light. It’s very important to be aware of all necessary conditions to grow onions properly.

Choose and prepare soil

Onions require very rich soils in which to sow and grow. Loamy-sandy soils and no clayey or very sandy soils are necessary, since they would not make the development and flowering of the onion possible. It has been shown that soils rich in potassium and nitrogen greatly favor the caliber of our onions. Also it’s important to check the Ph level of the soil as the appropriate range should be from 6 to 7.

Equally important is to select land that has not been planted with onion or plants of the same family (garlic, shallot, leek) at least one year before or in the previous season. If we know there has been an insect pest problem (mining worms, blind hens, etc) or diseases (purple spot, pink root, basal rot and woolly mildew) we should wait at least 4 years to grow onions.

We don’t want a heavy soil with excess moisture. As for example, waterlogging does not favor the planting of onions and their growth. It’s highly recommended to prepare the soil with sand and fresh manure to the ground a couple of months before, that way it will be rich in nutrients and ready to grow onions. In addition, a good trick is to add ashes to the ground.

If we do not have these requirements, we will have problems to harvest and also the development of the bulb will be limited.


There are 2 types of irrigation that can work to grow onions:

Gravity irrigation

The main characteristic of gravity irrigation is the way of distributing water in the soil. When the water advances over the soil surface, the distribution of the water in the plot and it’s infiltration in the soil profile occur simultaneously.

Drip irrigation

The water applied by this method of irrigation infiltrates the roots of the plants by directly irrigating the area of influence of the roots trough a system of pipes and emitters (drippers), which increase productivity and yield per unit area.

This advice on how to grow onions is very important since this plant should be watered frequently, in order for the soil to remain moist, during the plant’s growth stage. The frequency of irrigation of the bulbs should be progressively decreased while they are growing. When the harvest time of the onion is close, the irrigation must be stopped completely.

You should keep in mind that it’s very vulnerable to excess moisture and that sudden changes in temperature could cause cracking of the bulbs. It’s advisable to stop watering onions about 20 days before harvesting because we are interested that the soil is dry so that we can extract them correctly.

How to plant onions

The cultivation can be done with small onion seeds or inactive bulbs produced especially for planting. Sowing onions from their seeds is a cheap way to sow onion, however it also requires more work, while small inactive bulbs are sown directly in the garden. It’s preferable to plant bulbs than seeds, since this are the one that grow best and have the most strength. If it’s preferred to sow bulbs instead of seeds the best time to do it is in spring.

Holes are made every 15 cm along a line, 1 bulb is introduced into each hole and then the surrounding soil is squeezed so that it’s very firm.

If we’re going to plant seeds then planting is usually done in seedbeds and seedling transplantation in the place where they will grow is done between 40 and 60 days after it was sown. Seed germination usually occurs between the first and second week. The small bulbs must be planted directly in the final place, having a depth of 2 or 3 cm. The recommended space varies according to the onion crop, very often the measurements are 25.45 cm between the sowing lines and 10-15 cm between the plants.

Another top to keep in mind on how to grow onions since onions requiere regular moisture so weeds will appear frequently and it will affect directly their growth so we must eliminate those invasive plants since these can greatly affect onion crops, which is why it must be periodically removed so that the plant can grow healthy, always being careful not to damage the plants.

How to harvest onions

Once the stems protrude considerably and are also dropped to the side, it means that our onions are ready to be harvested. There comes a time when the vertices of the onion turn yellow. At this precise moment, it’s advised to twist them and break their necks. These must remain right there, remaining in contact with the earth. It will be at this time when onion ripening will begin.

To harvest the onion, the entire plant must be removed, without it’s leaves being released and then cured, this being the process where the onion loses excess water by exposing the bulb to the sun for 3 to 10 days in order to that this is sequenced, a few days should be left in warm climates with high luminosity and 10 days in regions of high altitude and with less sunshine. After this period when it’s observed that the leaves and the outer layer of the onion are completely dry it’s advisable to have them somewhere cool but not too cold. This will help in it’s conservation.

How to storage onions

Although onion is one of the vegetables that last the most, we can find a problem of now knowing how to preserve it. There are different methods for preserving onions both in a domestic and industrial level. Next we will give you the keys to keep and store onions in good conditions.

First of all the end of a season onions must be stored since those harvested in spring and summer do not hold so much and should be consumed in a few weeks after harvest. The ideal is so store the onions that are harvest in autumn since it endure all winter.

The onion variety is also important, for example spicy onions contain sulfur (which makes you cry) and helps preserve the onion in winter.

Domestic Storage

When choosing the right place for onion storage it’s very important not to place them near potatoes as the would absorb their moisture and spoil.

  • Do not use plastic bags to store them.
  • Find a dark place so they don’t spoil.
  • Choose a place that is at a constant temperature between 4C and 10C.
  • The storage space must be well ventilated and dry.

Industrial Storage

  • The bulb must have a low water content.
  • The bulb must be firm and compact.
  • It should not be fertilized with nitrogen during the last 6 weeks of cultivation.
  • It must have been harvested when it was fully mature.

Onion requires several operations before storage, one of the main ones is drying.

The objective of drying is to remove all surface moisture from the outer layers, thus sealing the onion and the stem. This process is intended to dehydrate the outermost layers. The appropriate temperature to carry out drying ranges from 25 to 30 C.

It’s storage will be carried out at constant temperature and humidity, avoiding fluctuations and in complete darkness, it must be taken into account that the bulb is still alive.

How to grow onions at home

Before starting to plant the onion we must prepare the soil that we will use in the pots; If for example, the soil is not rich in nutrients or too dry, although it’s irrigated continuously a fertilizer or natural fertilizer should be added.

An excellent advice on how to plant onion at homes is to avoid artificial fertilizers at all costs, because it’s very harmful to health, these should only be used to make the flowers beautiful. It’s for this reason that if we’re going to plant this plant for our consumption we must use natural fertilizers unless you want to use them as ornaments.

If we see that the land is poor, it must be fertilize fifteen to twenty days before we begin to cultivate. The depth of the pot should be 20 cm and 30 cm wide. Another point to consider when it comes to how to grow onions is that this plant should have a space of 15 cm between plantation. Once done the above we will start with the planting of onions.

To sow onion in pots we can use 2 methods, one is which the onion bulbs are planted directly, and another in which onion seeds are used, the latter being the method that takes the longest and in which greater care should be taken since the seeds must germinate in humid places that are warm at the same time.

If you are going to use the seeds you can put them in cotton or some toilet paper in a plastic bag with some water. This bag should be placed near a window with sun and heat, as we did in the primary to germinate seeds and can be a good experience to know how to grow onions in a pot.

Basic Tips

  1. It’s very important to keep onions free of weeds as they can stifle the plant.
  2. If the onion comes to bloom, it’s necessary to detach the floral stem. this is done to prevent premature flowering and benefit the formation of the bulbs.
  3. Onions are very sensitive to sudden changes in humidity, an abrupt change can cause cracking of the bulb.
  4. Ensure good moisture to the soil with irrigation, the recommended by drip to ensure optimal germination of seeds and plant development.

Source :

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