How to Plant Onion Sets

There are basically two ways you can grow onions in your vegetable garden – starting them from seed or planting onion sets.

Think of onion sets as transplants.

Bundle of Onion SetsOften the term “sets” is used for any onion bulb that is ready for planting.

These sets can be just the small bulb of the onion plant, or it can be complete immature onion plants.

Planting onion sets is pretty straightforward and simple enough.

Here’s how to plant onion sets in the vegetable garden.

How to Plant Onion Sets

The first thing you should do when planting onion sets is to amend the soil well with compost and organic matter where you intend to grow the onions. Onions enjoy fertile soil with very good drainage. Soil drainage is important for onions because if they stay too moist they could rot or mold could form on them.

Amend the Soil Well With Compost

Once you have the soil ready for planting remove the onion sets from the bundle or bag, and lay them out on top of the garden bed in the location where they will be planted. Onions do not need much spacing (depending on the variety) and can be planted fairly close together – about six inches apart.

Here, I am laying these ‘Exhibition‘ onions out with six inches of spacing in all directions. If you want to grow the large onion bulbs then space them at least six inches apart. If you are interested in using these as green onions, then space them as close as three inches apart.

Space the Onion Sets Out In the Garden Bed

Spacing them out like this will help to speed up the time it takes to plant. You will not need to measure the spacing out for each onion because it will be already in its spot.

I hope that makes sense…

So, with the onions spaced it is time to plant them. These ‘Exhibition’ onions need to be planted about one inch deep. Make sure to read the instructions that should be provided with your onion sets for proper planting dimension for your particular variety.

Simply take your finger and poke a hole in the soil about an inch deep and place the onion into the hole. If you are using the sets that are just bulbs make sure the pointy tip is facing up when planting.

Plant the Onion Set About an Inch Deep

With the onion in the hole work some soil around it and gently firm the soil up with the palm of your hand. Don’t mound too much soil up around the onion. Just enough to “fill” the hole and stabilize the onion set.

Finish Planting the Onion Set

Continue these same steps throughout the bed until you have all the onion sets planted.

Continue Planting the Onion Sets Throughout the Garden Bed

Once you have all the onions planted make sure to water them well. Give them a good soaking each day until they begin growing new green tops, then you can cut back the watering to every other day (depending on how much rainfall you receive).

It’s also a good idea to mulch around your onions to help suppress weeds, preserve soil moisture, and keep the onions cool during those very hot summer days.

If you don’t have an extra bed for growing onions, you can interplant them with lettuce, kohlrabi, and tomatoes. Avoid planting onions with peas and asparagus.

9 Comments on How to Plant Onion Sets

  1. Clarence Teague // May 6, 2011 at 8:00 am // Reply

    Whats happening Tee?, love the illustration on planting onions. Want to share with you something I do in my old red clay garden here in Newton, NC. I started trimming the roots off to look like a crewcut,and cutting the green tops off to just above where the white begins. I don’t know if this really helps them grow any quicker, but it seems they develop more evenly. Thanks for your sharing expertise. CLT

    • Hi Clarence,

      That is great advice for planting your onions. If the roots are very long then I agree that they should be trimmed. I normally just leave the green tops as they are unless they are all broken or brown. It is a good idea to trim them, though.

      Thanks so much for sharing how you plant your onions! Very helpful info 🙂

  2. I’ve got a small raised bed with several tomato plants and two pepper plants (tobasco and poblano). Would I plant onions around the same time, or do they have a different growing season?
    Also, thinking of adding garlic.

    • Hi Eliza – You can plant onions about the same time you plant the tomatoes. Garlic should be planted in the fall and then harvested the following summer.

  3. Jackie Vigeant // July 6, 2011 at 3:10 pm // Reply

    I have planted green onion bulbs for the first time and now the green part is about10 inches high and I can see part of the white of the onion.There seems to be a few onions on the same bulb, do I separate them and replant or will a bunch of green onions grow out of the one bulb ? Help!

    • Hi Jackie – I’ve never seen green onions grow as a bunch before. Did you plant them very close together? I wouldn’t try to separate them because that may kill them. I think the best thing you can do at this point is let them grow and see what happens. You can also trim off a few inches of the green tops and use them. They will grow back.

  4. This is very helpful information. I am excited about starting my garden. Thanks Tee for all of the advice.

  5. Every year my onions never get over the size of a quarter. I live east of Dallas,Tx. I always plant them around the first of feb. iI have sandy soil where i live. Can you tell me what to do to grow nice larger onions

  6. what do you use to fertilize the onion sets?

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