Tag: how to grow onions

How to Grow Onions: All You Need to Know

How to Grow Onions: All You Need to Know

bowl with fresh onions on marble table
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If your are interested in learning how to grow onions I have good news for you! This cold season crop is hardy and easy to grow for gardeners of all skill levels. Some people may recommend that you plant your onions in the fall but its not too late, you can plant and have a successful harvest even if your start in the spring.

How to Grow Onions From Sets

Step 1: Choose your Onions

To start you need to know what kind of onions you want to plant. We like to plant a mix of yellow and red onions. Now that you know what kind to plant you have to decide whether or not you want to grow onions from seeds or from sets. We recommend that you plant onion sets. Onion sets make the process easier, faster, and increase the likelihood of a successful crop. Sets are small onion bulbs that you can buy from your local gardening center or farm store. Onion sets can also be planted without worrying about frost damage!

Step 2: When to Plant your Onions

Fall Planting:

If you plan on planting your onions in the fall it is important that your onions have around 4-6 weeks of warm weather. If you plant too late into the season they may not have the time they need to establish themselves in the soil. The crop will remain dormant during the winter and then continue to grow in the spring. One benefit of planting in the fall is that it increases the size and improves the flavor of the onions you plant. If your region experiences cold winters it will be best if you plant in the spring.

Spring Planting:

If you are planting in the spring (and using onion sets not seeds) plant when the weather is cool but not cold. You don’t want to plant your onions if the temperatures reach below freezing.

Step 3: Deciding Where to Grow your Onions

The first step in growing great onions is make sure you have great soil. It should drain well and be lose as well as fertile. To increase the fertility of the soil add compost to your soil as onions require lots of nutrients as they grow. Onions require full sun (at least 6 hours a day) so picky a sunny spot in your garden.

  • Pro Tip: Add an inch or two of compost to the base of each row prior to planting.

Step 4: Plant your Onion Sets

Plant your Onion sets around 1 to 1/2 an inch deep and 4 to 6 inches apart depending on the size of your bulb. Make sure the rounded end is pointing down and the pointy end is facing upward. Next you should cover the onions with about 1 inch of soil. After this put a layer of mulch 1/2 an inch thick on top to lock the moisture in and restrict weeds.

Step 5: Care for your Onions

If you want large onions it is important that you fertilize every couple weeks with nitrogen. Make sure to stop fertilizing once the onions start to push the soil away and the bulbing process has begun. leave the pushed back soil where it is. The onions have to emerge above the soil.

When it comes to watering, onions are a breeze. They do not require constant watering. You should be giving your onions around 1 inch of water per week.

  • Pro Tip: If you want your onions to be sweeter, give them extra water

Step 6: Harvest

Similar to growing potatoes and growing garlic, when onions begin to mature the foliage will become yellow and start to wilt/fall over. At this point you can bend the tops to speed up ripening. When the foliage has turned brown it is time to pull up your onions. The harvesting should be done by late summer or you risk having your onions spoil in the cooler fall weather.

  • Pro Tip: Loosening the soil surrounding the bulbs can encourage drying.
Garlic on cutting board
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How to Grow Onions From Seeds

If you are going to grow onions from seeds you should be aware that it is a much longer process. You will have to begin by growing your seeds indoors in January or February depending on the region you live in.

Step One: Select your Onion Seeds

It is important to know that your onion seeds will not last long in storage so purchase your seeds the year you plan on growing onions. You should also select onion varieties that will grow well in your area. The types are; short-day onions (triggered when sunlight reaches 10 hours a day), day-neutral onions (12 hours of sunlight a day), and long-day onions (14 hours of sunlight a day)

Step Two: Begin Indoors

For this step you can use pretty much any container you can get your hands on. You could use empty egg cartons, berry containers etc. You will want to fill the containers of your choosing with seed starting mix. Sprinkle the seeds evenly on top of the soil and then mist with water. Afterwards cover the seeds with more soil. An eighth of an inch should do the trick.

Next label your containers appropriately if you’re starting more than one kind of seed inside. Put your containers in a water proof container and place in a warm area to increase humidity and encourage seed growth.

After the seeds have sprouted remove your little containers from the water proof container and place under growing lights if your area doesn’t get enough sun during the winter.

Keeping the soil evenly moist is vital at this stage. You can also fertilize with some compost tea.

Make sure to trim the tops of the onion seedling to keep them around 3 inches tall. This will prevent the stalks from stealing nutrients that the bulbs need.

Step Three: Hardening

Never heard of hardening? Or are you a hardening pro? Either way sometimes a refresher is nice. Hardening is the process of adapting your indoor plants to the outdoor environment. Place your seedlings outside, preferably in a covered location, for a few hours the first day. Then increase the amount of hours daily until they can manage being left outside overnight.

Step Four: Transplanting

Onions are not plants that grow well in limited sunlight. They need full sun, which is at least 6 hours of direct sunlight everyday.

Start the transplant by removing the seedlings. Do this carefully. You may need to turn the container over and slowly works the seedlings out.

Plant the seedlings 4 inches apart. Don’t plant them very deep, 1 inch should do it. Cover the roots with soil and water them. Seedlings will require more water than sets when they are first starting out. Make sure to cover with mulch or straw after watering to lock moisture in and keep weeds out,

brown shovel
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There are two pests you need to watch out for while growing your onions.


Thrips are small insects that might be hard to spot. To check if your onions are infested, simply smack dark fabric or paper against the onion tops. The thrips tan-colored bodies should show up on the paper or fabric. If you find thrips don’t panic. Simply spray your plants twice, three days apart with insecticidal soap.

Onion Maggots:

Dealing with onion maggots is a little more difficult than with thrips. To prevent and deal with onion maggots you can cover you emerging crop with fine mesh netting. Onion maggots like to lay eggs at the base of plants so this will prevent them from doing so. It will also help to remove any mulch you may have covered your onions with.

Tips for Growing Onions

  • Crop rotation is important if you plan on growing onions more than one year in a row.
  • You can sow leafy greens between your rows of onions to help suppress weeds.