How to Grow Red Onion: Complete Planting and Growing Guide

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Culinary enthusiasts love red onions for their sweet taste and attractive dark color. If you like cooking and experimenting in your kitchen garden, red onions can be the perfect crop for you to grow.

They are relatively low maintenance and do not take a lot of space to plant. You can even grow red onions in pots if you are short on space.

We have provided an extensive yet easy to follow, step-by-step tutorial on how to grow red onions at home, with some additional tips and tricks to help you acquire a healthy yield.

How to Grow Red Onion’s?

How to Grow Red Onion's

#1. Planning Your Crop

Onions are biennial crops. In other words, they have a life cycle of two years. During the first year, the seeds grow into small bulbs and develop roots. In the second year, these bulbs grow into a full-sized onion.

You can grow your onions using any of the following methods:

  • Using onion seeds
  • Using onion sets (onion bulbs that have completed the first year of their biennial cycle)
  • Using another fully grown onion

No matter how you choose to grow your onions, the first step is to prepare the soil.

#2. Prepare The Soil

To ensure your onions grow into healthy and large bulbs, you need to have the proper growing medium. Follow the below-mentioned steps for creating the most nourishing growing medium:

  • Use only well-drained and loose soil as clay soil can cause your roots to rot.
  • Use soil with a neutral pH of around 6.0 to 6.8.
  • Mix organic compost into your soil before planting.
  • Feel free to add cow manure or chicken manure to your soil.

Before and after you mix compost and manure, loosen your soil with a garden rake. This will aid in creating a nutritious blend of its components and assist in soil aeration.

Also, make sure that there are no rocks or weeds in your planting medium before you plant.

Once your growing medium is prepared, you can decide which method of planting you want to use. To help you choose the best approach, we have provided a detailed guide for all commonly used methods below.

In contrast, you may want to consider growing red onions in raised beds in a humid climate.

Bonus Read: Maggots in Compost: Are They Good or Bad?

#3. Climate Requirements

Onions are hardy crops and can grow in almost all types of climate, except overly humid regions. So, if you are a beginner DIY gardener, you will not have to worry about constantly monitoring your crops.

Climate Requirements

Onions love sunshine, so choose a spot that gets a lot of direct sunlight throughout the day. Additionally, apart from being frost-tolerant crops, they also grow best in regions with a cool, dry winter.

#4. Growing Red Onion From Seeds

You can easily find onion seeds in a garden supply store. Although, you should know that starting your own seeds requires plenty of patience and care.

Growing Red Onion From Seeds

If you want to start your seeds, you need to follow these instructions:

  1. Sow your onion seeds in an indoor container. You can even use empty egg cartons to plant your seeds.
  2. If you are using a container, space your seeds about one centimeter apart.
  3. Make ¼ inch or 1-inch holes with the end of your garden trowel.
  4. After that, cover the seeds in a thin layer of compost and nitrogen-rich potting soil.
  5. Soak your soil after planting.

After you plant the seeds, water them at least one to three times a week. An easy way of understanding how to water your seeds is to water until your soil is saturated. After that, please wait for it to dry completely before watering again.

If you are growing your seeds indoors, germination may take a few weeks. Be patient, and you will soon witness your seeds germinate into springy little seedlings.

Once your seeds have germinated into around six-inch seedlings, they are ready for transplantation.

#5. Transplantation

Remember, once you plant your seedlings, you cannot move them at all for the next two years. We have provided the best steps for the successful transplantation of your red onion saplings.

  1. The best time for transplantation is around late March or early April.
  2. Choose a sunny spot with loose and aerated soil.
  3. Space your seedlings four to six inches apart to provide adequate space for the growing bulbs.
  4. If multiple rows are being planted, they should be at least six to twelve inches apart.
  5. Soak the soil after planting for the first time and wait till it’s dry again before watering.

Caution: Over-watering can lead to your bulbs rotting. Keep your soil moist, not soaked, and only water when you observe the soil is becoming dry.


If you want larger bulbs, you can place the rows farther from each other. In this manner, your harvest will yield fewer onions, but they will be more prominent in size. In contrast, if you want a larger quantity of onions but smaller buds, space the sapling closer to each other.

Once planted, your seedlings will grow rapidly. After just a month of planting, they will grow up to 18 to 24 inches in height, which is their maximum possible length,

After this, the bulbs will grow till harvest time.

#6. Growing Red Onions From Sets

Sets are the most commonly used method of growing onions. They are small, dormant onion bulbs that are ready to germinate.

Sets are more suitable for amateur gardeners or those who simply want to eliminate the extra steps involved in setting their seeds. Moreover, many kitchen garden enthusiasts prefer sets as they reduce the time of harvest.

The steps for growing onions from sets are:

  1. Pick the larger and firmer seeds instead of the small, soft ones, as they have a better chance of growing into large bulbs.

  2. Spacing for sets is the same as that of seeds mentioned above.

  3. Using a digging tool such as a trowel, make a one-inch hole for each seed.

  4. Carefully place the root end of your bulb facing the ground.

  5. Water thoroughly and wait for your soil to dry before watering again.

#7. Growing Red Onion From Another Onion

Growing red onions from another onion can be a cheaper alternative to both seeds and sets. You can start from the comfort of your home, as no visits to the gardening supply store are required.

Growing Red Onion From Another Onion

Use our guidelines for successfully growing your red onions through this method.

  1. Peel the outermost papery layer of the onion.
  2. Make a lengthwise cut using a sharp knife while ensuring you don’t slice through the bulb.
  3. Separate the two halves of your onion and remove the bulb.
  4. Submerge the bulb in a glass of water until it sprouts.
  5. Place your sprouted bulb in your growing medium just as you would do with a seedling.
  6. Saturate the soil with water and wait until it is dry again before watering.

Additional Instructions For Growing Red Onions

Here are a bunch of additional instructions that will prove instrumental in growing a nutritiously rich harvest:

  • We suggest planting your onions at least six weeks before your last frost date, as onions grow best when the temperature is around 20ºC.
  • Onions have shallow roots and require a lot of water. However, overwatering can read to rot, which will destroy your crops.
  • No matter what method of planting you choose, you must remember never to overwater your onions and ensure they are in direct sunlight throughout the day.
  • It is best to plant your onions in a separate area with no large trees nearby, so they are not under shade any time of the day.
  • You can spread mulch around your seeds or bulbs but never cover the opening as too much moisture can kill the mulch.
  • Cover your seeds with a thin layer of compost and potting soil mixture for added nutrition.
  • Depending on the climate, you should only water the onions every three to four days at most.
  • Always remove weeds as soon as you spot them and frequently check for any signs of weed growth.
  • If you are worried about bolting, consider using seedlings rather than sets, as they are less likely to bolt.


Growing onions is a long process, but it can be incredibly rewarding. If you planted your onions around February-March, they should be ready to harvest around late October or November. You can predict if your onions are ready to harvest by spotting any of the following signs:

  • If you are looking for scallions only, you can simply pull them out a few weeks after planting.
  • If you are looking for full-grown onion bulbs, keep an eye on the green tips drying up and turning yellow.
  • You can stop watering if you see that around 10 percent of the tips have turned yellow.
  • When the leaves have tipped and fallen over, it is a sign that your onions have grown the largest they can get.
  • It is straightforward to harvest your onions once they have attained full maturity. You can do it with a spade or simply by using your hands.
  • Dig around the onion while avoiding the bulb and pull it out.
  • To get a cleaner result, try twisting the onion until the roots are loose and most of the soil has fallen off.
  • Once you have all your onions, store them in a warm, dry place with good air circulation to cure with the tops attached.
  • Fresh onions usually take around ten days to cure, after which the roots dry off, and the outer layer becomes paper-like and flaky.

Additionally, at this point, you may remove the top with shears or just store them as it is, depending on your preference. Always choose a cool, dry space for storage to keep your onions rot-free, as some pests may affect cured onions in storage as well.

Companion Crops

If you want to reap the maximum benefits from your soil, you may want to consider companion cropping when you grow red onions.

Companion Crops

In companion cropping, two or more crops are grown close to each other to enhance the flavor of the individual crops and as a preventative measure against pests.

Here are some companion plants suitable for growing with red onions:

  • Lettuce
  • Cabbage
  • Strawberries
  • Swiss Chard
  • Beets
  • Leeks
  • Carrots

Bonus Read: How to Grow and Care for Swiss Chard?

Pests and Diseases Commonly Affecting Red Onions

Pests and Diseases Commonly Affecting Red Onions

No matter what crop you choose to grow, there is always a risk of diseases or pests wreaking havoc on your beloved plants. Keep an eye out for these crop diseases and pest attacks to keep your red onions in the pink of health.

Onion Maggots

Onion maggots are one of the most common vegetable pests. The females can lay eggs at the base of the seedling, and the offspring grow up feasting on the prized bulbs.

The damage spreads throughout the crop as the maggots move from one plant to the other in search of food and to lay more eggs. It often becomes difficult to control these pests once an infestation has already taken place.

To prevent onion maggots, you need to maintain excellent crop sanitation. Always remove weeds and throw away any remaining culls to prevent attracting maggots and other pests.

If you see signs such as wilting leaves or fuzzy growth on onions, use pesticides immediately and dig up the infected onions with a gardening spade.

Downey Mildew

Downey mildew is a fungus that usually attacks the onion leaves and gradually spreads lower to the bulbs. It is also seen in leeks and garlic.

Your onions may have Downey mildew if you notice the leaves growing a pale green color before slowly turning yellow and collapsing entirely.

If you use a sprinkler irrigation system, your crops are more susceptible to Downey mildew as the fungi require wet leaves. Cold climatic conditions with high humidity are the ideal environment for a Downey mildew infection.

If your leaves are affected, immediately use a pesticide to kill the fungi and stop spores from spreading to other plants.

Onion Pink Root

Onion pink root is another fungal infection that can be a result of contaminated soil or gardening equipment. The roots turn into a pink-red color before darkening to black and dying.

Although pink root usually does not kill the plant, it can cause the bulbs to be smaller as they will be deprived of adequate nutrition.

Preventive measures are the best way to avoid a pink root infestation. Crop rotation, soil fumigation before planting, and using resistant varieties of onions are the best forms of protection against pink roots.


Leafminers are minuscule insects that attack the leaves of onions. They usually do not cause any serious harm to the crops and do not affect the bulb at all.

However, if you plan on harvesting scallions along with your red onions or have any other leafy vegetables growing nearby, leafminers can be a severe problem.

The best way to get rid of these pests is through the use of pesticides. You may want to use a rotating variety of pesticides to avoid pesticide resistance.

Apart from that, preventive measures such as thoroughly checking the field for larvae before planting and working the soil with tools like hoes can prevent future leafminer attacks.

Bonus Read: How to Get Rid of Aphids in Your Garden


Red onions are a beginner-friendly crop with low investment and rewarding results for gardeners around the globe.

If you have recently started home gardening or are looking for an easy crop for your crop rotation purposes, red onions can be a blessing in disguise!

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