How to Plant Onions

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Onion Sets

This year I’m growing my onions from sets. They’ve been in the ground for two weeks, and they’re already off to a great start. If planting onions is still on your to-do list, here are step-by-step instructions to take you through the process.

Growing Onions from Sets

While you can grow onions from seeds, transplants or sets; I recommend growing them from sets. Onions sets look like little onions bulbs, and that’s exactly what they are. Someone has grown them from seed, and forced them into dormancy to give you a head start on your garden. And that head start translates into bigger onion bulbs at harvest time.

You can order onion sets from any number of garden catalog companies, but I’ve found it’s a lot cheaper to buy them from my local co-op store. I paid $1.59/lb for my sets this year. Sets don’t weigh much, so you’ll get a ton – even if you only buy a pound.

Since stores like co-op cater to farmers, you can be confident that they’re selling onion varieties that are actually suited to your area. Not all onions are.

There are basically three types of onions for you to choose from: short-day, long-day and day-neutral. Generally speaking, long-day onions are intended for growing in the north. Short-day onions are intended for growing in the south. And day-neutral (or intermediate-day onions) can be grown anywhere. Once you know that, it’s easy to pick out a variety that will do well in your garden.

Alright, now that we have all of that sorted out, let’s get busy planting some onions!

Onion Planting Depth and Spacing

Onions need to be planted two-inches deep and three to four inches apart. To avoid digging a gazillion holes, I had my husband build me a dibble that stamps nine holes at a time.

Instructions for building a dibble

Dibble for Square Foot Planting

This is what my dibble looks like. It’s sized to do a square foot of garden at a time. We designed it to make two-inch deep holes that are spaced four inches apart, so it’s perfect for planting onions, garlic and a bunch of other things. Check out my dibble planting guide for a complete list of things that you can plant with it.

Dig Holes for Onions

When I plant onions in one of my 3’x6′ beds, I only have to stamp my dibble 18 times. Compare that to the 162 holes that I would otherwise have to dig by hand, and you can see what a useful tool it is.

But you don’t have to have a dibble to plant onions. If you don’t have one, or don’t want to bother with building one, just dig your holes by hand.

Planted Onions

Then, once you have your holes, just drop an onion set into each one (pointy end up), and cover the holes back over with soil. Be sure to give the bed a good watering, and that’s really all there is to it.

When to Plant Onions

Onions should be planted in early spring, about four to six weeks before the last frost date for your area. If you live in the south, you can also plant onions in the fall, two to four weeks before the first frost. Be sure to mulch the bed heavily, if you’re doing a fall planting.

Onion Growing Tips

  • Weed your onion bed regularly with a hoe, but avoid pulling weeds, as this may damage the onion roots. Mulching is a great way to cut down on the weeds in the bed
  • Onions require an inch of water each week. Be sure to water them during dry spells
  • Opt for a keeping onion, if you want onions that store well. Keeping onions have thicker skins, and are usually on the drier side. Seed catalogs will usually note which onions are good for long-term storage

Companion Plants for Onions

Improve flavor and minimize pest problems by practicing companion planting. Here are some good companions for onions.

To Deter Onion Fly, Plant Your Onions With …

  • Carrots

To Improve Growth and Flavor, Plant Your Onions With …

  • Beets
  • Cabbage
  • Chamomile
  • Leeks
  • Lettuce
  • Strawberriers
  • Summer savory
  • Tomatoes

Do Not Plant Onions With …

  • Asparagus
  • Beans
  • Parsley
  • Peas

How Many Onions Should I Plant?

For a year’s supply of onions, plan on 15-20 plants per person. If you plan to use your onions in canning projects, or your family just eats a lot of onions, you may need to plant more.

More Spring Planting Guides:

How to Plant Strawberries
How to Plant Asparagus
How to Plant Garlic
How to Grow Potatoes in Cages
How to Grow Mushrooms on Logs

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  1. Erin, great post about planting. This is definitely a hobby I wish I could spend more time partaking in but currently can’t due to my apartment constraints.

    1. Hi Tammi, Onions are ready for harvest about two weeks after the tops brown and fall over. For spring planted onions, that will be some time in the summer, for fall planted onions that will be some time in the spring. I don’t know what zone you’re in (or when specifically you planted yours), but it’s possible that it got too cold for them this winter. I wouldn’t give up on them yet, though. With the weather warming up, they may just surprise you and spring into action.

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