Most people plant onions in the spring, but did you know that planting onions in the fall makes for larger onions? The secret to growing large onions then, is actually to plant them in the fall – this way, they get a head start in the fall, go dormant in the winter, and spring back up again in spring! What's even better is that you'll be able to harvest them even earlier when you plant them in the fall. Keep reading to learn the exact science in growing large onions in the fall and have the best onion harvest ever!

Growing Large Onions in the Fall

onion harvest

Soil Prep:

  • Prep the soil by separating it, and making sure it's loose and fertile.
  • Add in some compost to help loosen the dirt, and, if your soil contains a lot of clay, add in some sand to help loosen the hard dirt.
  • We recommend growing onions from bulb sets, as growing them from seed can take a lot of time and can have a hard time becoming established.

When & How to Plant:

  • Plant your onions about 4-6 weeks before the first frost in the fall. This usually means in September, but depending on where you live, it can be as late as October.
  • Dig about an inch or two deep, and plant the bulbs with the pointy end up. Cover back up with soil.
  • Mulch with 1/2″ layer of straw or shredded leaves to keep weeds at bay and help retain moisture.
  • If you're planting from seeds, plan to plant earlier in the season and plant 1/4″ deep.


  • Once the onions have pushed through a little bit, they'll need a heavy layer of mulch to protect them from the cold days.
  • Add an inch or two of mulch over your protruded onions to keep them safe from frost.

By the end of spring, your onions should be ready for harvest, and you'll notice they'll be a lot of bigger than spring-planted onions!

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Growing Large Onions

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