Easy Steps to Grow Onion: Planting Onion Sets the Right Way

Last spring, my neighbor Doug walked over to my garden bed holding a mesh bag of onion sets and a confused look on his face. “I bought these at the feed store,” he said. “Now what?” I laughed because I had the exact same moment about six years ago. I stood in my backyard with a bag of tiny onion bulbs and zero clue what to do with them.

The good news? Planting onion sets is one of the simplest things you can do in a garden. If you can dig a small hole and drop something into it, you can grow onions. Seriously. I’ve watched kids do it. I’ve watched people who have never touched dirt in their life pull it off on the first try.

So let me walk you through the easy steps to grow onion from sets — the same way I showed Doug, and the same way I do it every single year.

What Are Onion Sets?

Onion sets are small, dormant onion bulbs grown from seed the previous season. They are planted directly into the soil and grow into full-sized onions in about 90–120 days.

Why Onion Sets? Because They Just Work.

Before we get into the steps, let me explain why I always tell beginners to start with onion sets instead of seeds or transplants.

Onion sets are small, dormant onion bulbs. They look like tiny onions — about the size of a marble or a dime. You can find them at most garden centers, hardware stores, and even some grocery stores in early spring.

Seeds take forever. I’m talking 4 to 5 months from seed to harvest. And they need babysitting — indoor lights, seed trays, constant moisture. For a new grower, that’s a lot of work before you even get something in the ground.

Transplants are fine, but they’re harder to find in some areas. If you’re gardening in the Southeast or Midwest, your local nursery might carry them. But in a lot of smaller towns, onion sets are what’s on the shelf.

Sets give you a head start. They’re already past the fragile seedling stage. You stick them in the ground, and they grow. That’s it. A friend of mine in central Texas told me she planted onion sets in a raised bed she built from old fence boards. She forgot about them for two weeks. When she came back, they had green shoots poking up like little flags. That’s how forgiving sets are.

Quick Guide: How to Plant Onion Sets

1. Prepare: Create a 1-inch deep trench in loose, well-draining soil.
2. Space: Place sets 4–6 inches apart (6 inches for larger bulbs).
3. Orient: Always plant the pointed end up and the flat (root) end down.
4. Cover: Fill the trench with 1 inch of soil; the tips can slightly peek out.
5. Firm: Lightly pat the soil to ensure contact between the bulb and dirt.
6. Water: Give them a deep, gentle watering immediately after planting.

Planting Onion Sets (Recommended Method)

Alright, here’s the step-by-step. Grab your sets, a hand trowel or hoe, and let’s get to work.

Step 1: Dig a Shallow Trench About 1 Inch Deep

You don’t need to dig deep. One inch is all you need. Think of it like making a line in the sand with your finger — just a little groove in the soil.

I use the edge of a hoe and drag it along the row to make my trench. Some people use a stick or even the handle of a rake. There’s no fancy tool required.

A mistake I see a lot of first-time growers make is digging way too deep. If you bury onion sets 3 or 4 inches down, they’ll struggle to push through the soil. They might still grow, but you’re making it harder than it needs to be. One inch. That’s the sweet spot.

If your soil is heavy clay — and I know a lot of folks deal with that, especially in parts of Georgia, Alabama, and the Ohio Valley — loosen it up a bit before you dig your trench. Break up the clumps. Mix in some compost if you have it. Onions like loose, well-drained soil. They don’t want to sit in thick, wet clay.

Step 2: Place Your Sets 4 to 6 Inches Apart

Spacing matters more than most people think. I learned this the hard way.

My first year growing onions, I crammed about 40 sets into a 2-foot row. I figured more onions in less space meant a bigger harvest. Wrong. What I got was a bunch of marble-sized onions that never filled out. They were fighting each other for nutrients, water, and room to grow. It was like trying to fit ten people in a five-person tent — nobody’s comfortable.

Give each set 4 to 6 inches of breathing room. If you want bigger bulbs, go with 6 inches. If you’re growing green onions (scallions) and plan to harvest them young, 4 inches is fine.

I usually eyeball the spacing. You don’t need a ruler. Just spread your hand out — the distance from the tip of your thumb to the tip of your pinky is roughly 7 to 8 inches for most adults. So place your sets a little closer than that, and you’re in the right range.

If you’re planting multiple rows, keep the rows about 12 to 18 inches apart. This gives you room to walk between them, pull weeds, and water without stepping on your plants.

Step 3: Position the Pointed End Up

This is the step people mess up the most. And honestly, it’s the step that matters a lot.

Every onion set has two ends. The bottom is flat or slightly rounded — that’s where the roots come out. The top is pointed — that’s where the green shoot grows from.

Pointed end up. Flat end down. Say it like a mantra while you plant.

I had a buddy in North Carolina who planted an entire row of onion sets upside down. They still grew — onions are tough little things — but they came up crooked and took longer to sprout. The shoots had to curve around the bulb to find their way to the surface. It cost him about a week of growing time compared to the ones he planted right-side up.

So save yourself the trouble. Pointed end faces the sky.

If you grab a set and you’re not sure which end is which, look for any tiny dried roots on one side. That’s the bottom. Or look for the papery tip that comes to a point. That’s the top.

Step 4: Cover with 1 Inch of Soil

Once your sets are sitting in the trench with their pointy ends up, gently push soil back over them. You want about 1 inch of soil on top. The very tip of the set can even peek out a little — that’s perfectly fine.

Don’t pack the soil down hard at this point. Just loosely cover them. Think of it like pulling a light blanket over someone. You’re not tucking them in tight. You’re just covering them up.

I’ve seen new gardeners pile 3 or 4 inches of soil on top because they think the onions need protection. They don’t. Too much soil and the bulb has to work overtime to push a shoot to the surface. Remember: onion sets are close-to-the-surface growers. As they mature, the bulbs will actually push themselves partly out of the ground. That’s normal. Don’t bury them back down when that happens.

Step 5: Gently Firm the Soil Around the Sets

Now — and only now — give the soil a gentle press with your hands or the back of a rake. You want good contact between the soil and the sets. This helps the roots make connection with the dirt and start pulling in moisture.

But gentle is the key word here. You’re not stomping on it. You’re not packing it like you’re making a sandcastle. Just a light pat.

I think of it like pressing down the soil on a potted plant. Firm enough to hold everything in place. Loose enough that water can still drain through.

If you press too hard, you can compact the soil around the set. Compacted soil holds too much water and not enough air. Onion roots need both. Compacted soil can also lead to rot — and there’s nothing sadder than pulling up a mushy, rotten onion that should have been a beauty.

Step 6: Water Thoroughly

Right after planting, give your onion bed a good, deep watering. You want the soil moist all the way through the root zone — not just damp on top.

I use a watering can with a gentle rose head for my onion rows. A garden hose on a soft shower setting works too. What you don’t want is a hard blast of water that washes the soil off your sets and sends them rolling down the bed. Ask me how I know. My first year, I turned the hose on full blast and watched half my sets float to the end of the row like tiny boats.

After this first watering, keep the soil consistently moist for the first couple of weeks. Onion sets are waking up from dormancy, putting out roots, and sending up shoots. They need steady moisture during this time.

Once they’re established — you’ll see green tops about 3 to 4 inches tall — you can back off a little. Onions like about 1 inch of water per week. In dry spells, especially during summer in places like Kansas, Oklahoma, and parts of the Southwest, you may need to water twice a week.

But don’t overwater. Onions sitting in soggy soil will rot from the bottom up. If your soil stays wet for more than a day after watering, you may need to improve drainage. Raised beds help a lot with this.

A Few Things That Trip People Up

Since we’re talking about easy steps to grow onion, let me mention a few common problems I see — and how to avoid them.

Planting at the wrong time. Onion sets go in the ground in early spring, as soon as the soil can be worked. In most areas, that’s 4 to 6 weeks before the last frost date. Onions can handle light frost. They actually prefer cool weather to get started. If you wait until May or June in most of the U.S., you’ve missed the window. The days are too long and hot for the bulb to develop right.

Choosing the wrong type. Onions are day-length sensitive. Short-day varieties work best in southern states. Long-day varieties are better up north. If you plant long-day onions in Louisiana, you’ll get tiny bulbs. If you plant short-day onions in Minnesota, same problem. Check the label on the bag or ask at your garden center.

The Day-Length Rule:

Long-Day: Best for the North (shines with 14–16 hours of sun).

Short-Day: Best for the South (bulbs with 10–12 hours of sun).

Intermediate-Day: The “neutral” choice for the middle of the country.

Ignoring weeds. Onions are terrible competitors. Their leaves are thin and upright, so they don’t shade out weeds the way squash or tomato plants do. A weedy onion patch is a sad onion patch. Keep up with weeding — especially in the first month. Mulch with straw or grass clippings (no seed heads!) to keep weeds down and hold moisture in.

Skipping fertilizer. Onions are hungry plants. A side dressing of balanced fertilizer or compost tea every few weeks during the growing season makes a real difference in bulb size. Stop feeding once the bulbs start to swell and the tops begin to fall over — that’s the plant telling you it’s finishing up.

Final Thought

Growing onions from sets is about as straightforward as gardening gets. Six simple steps. A little patience. And in about 3 to 4 months, you’ll be pulling fat, golden onions out of the ground with your bare hands.

Doug — my neighbor — harvested over 30 onions from his first planting. He brought a bag of them to a neighborhood cookout and couldn’t stop talking about it. There’s something genuinely satisfying about growing your own food, even something as humble as an onion.

So grab a bag of sets, pick a sunny spot, and get planting. Your future self — the one standing in the kitchen slicing a homegrown onion — will thank you.

Frequently Asked Questions