How Deep To Plant Onion Bulbs

Onions are easy to grow, especially from sets, and can produce a good crop with little care. Nevertheless, harvesting those flawless large bulbs takes a bit of expertise that many novice gardeners fail to offer. Even the seemingly insignificant details, such as the planting depth, can make all the difference in setting the fate of the harvest. Read on, and you’ll learn just how deep to plant onion bulbs in the ground for the best crop.

You should know exactly how deep to plant onion bulbs to help develop the best harvest. Planting the bulbs too deep or setting them too shallow in the soil can both be a problem.

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how deep to plant onion bulbs

Why Does Planting Depth Matter

The key to a good start for an onion crop is the correct planting depth. If you don’t plant them deep enough, they’ll take a longer time to get started. Onions will take longer to develop, and you might not get full-sized bulbs by the end of summer. Planting the onion bulbs too deep will, again, hinder bulb development. Though deeply planting the onion sets might not affect green growth, the size of the bulbs produces by the end of summers might not be as big as suggested for the variety. 

If you’re simply growing onions for the green tops, planting depth wouldn’t matter much as such. However, growing big, flavorful bulbs takes a little more skill and attention to detail. Besides planting at the correct time, you also need to take care of the planting depth to make sure bulbs develop fully in time before the cool weather of the fall sets in. 

See also  How To Fertilize Onion Plants (And When)

How Deep To Plant Onion Bulbs?

Most gardeners recommend planting the onion sets no more than an inch deep in the soil. Avoid pushing the onion sets down in the soil as this compacts the soil around the roots. Dig a hole and pit the onion set bulb with the root end facing down and the tip facing upwards.

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Draw the dirt up without compressing the soil around the bulb. Make sure there’s no more than 1 inch (2.5 cm) of soil above the tip of the onion sets. Water the crop right after planting and offer an inch of water per week throughout the growing season for best development. 

What To Do If You Plant The Bulbs Too Deep?

If you’ve already planted your onion bulbs deeper than recommended (deeper than 1 inch below the soil surface), don’t worry. The problem can still be fixed. Just leave the bulbs be in their place for the first couple of weeks. As soon as the bulbs start expanding, push away some of the dirt from the sides to give them more room to develop and grow bigger. As long as they’re allowed some space to expand above the soil, you should expect a decent crop before the fall season. 


Now that you know how deep to plant onion bulbs, make sure you set them correctly in the soil to ensure the best harvest this summer. Click here for my full guide on how to plant onions from bulbs.

4 thoughts on “How Deep To Plant Onion Bulbs”

  1. Still don’t know how deep to plant them. The tops are growing but I don’t see bulbs. When will I start seeing the bulbs.

    • Hi Marth, thanks for the great question. Onions typically take 90 to 100 days to grow. You should see the bulbs start to swell after 45 days.

    • short day onions can go in the ground mid november to mid january and long day onions can go in the ground from jan to early april


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