When to Harvest Onions: A Guide for Gardeners

Did you know that approximately 100 million tons of onions are grown worldwide annually?! That amounts to a lot of delicious umami dishes, sharp pungent bites, and watery eyes all around. But do you know when to harvest onions?

Onions are a staple in many cuisines because of their flavor, versatility, and storage capability. We love to plant and harvest delicious organic onions at home, enjoying them throughout the winter and into spring.

But how can you tell when onions are ready to harvest? In this guide, I'll tell you how to know when to harvest onions, how to harvest onions, and how to cure and store onions long-term. 

The Spice of Life

Gardening is my passion, and I love inspiring others to grow a garden, live healthier lives, and have fun doing it. I want everyone to enjoy an organic garden that provides a variety of nutritious foods, new experiences, and fresh excitement each season.

Now that you know how to grow onions, I challenge you to spice up your life this year by mastering a new skill, like learning how to grow garlic, making compost at home, making a DIY tower garden, building a grape vine trellis, or learning how to cure onions.

How to Prevent Onions From Bolting

You may wonder how to prevent onions from bolting before they’re ready to harvest. The answer may surprise you: start your onions from seed, not from onion sets!

Onions are biennials, meaning they focus their energy on growing their bulb the first year and on flowering and producing seeds the second. Many onion growers grow immature onions, store them, and sell them as onion sets for the next season. 

Bolting, or prematurely producing a flower, usually happens in the second year. Onions started from sets often have a green center that will never fully cure! (That green center is the flower stalk.)

If you grow from onion sets, you may need to cut the flower stalk off and use the onion much sooner. Growing from onion sets produces onions with smaller bulbs and reduced storage shelf life.

Knowing When to Harvest Onions

Onions take a long time to mature and need all the time in the ground you can give them. It’s tempting to harvest onions too early, so it’s important to learn when they’re ready to harvest.

Onions are ready to harvest when the neck of the onion crimps and the tops fall over. This happens because the neck dries up. (The neck is where the onion leaves meet the bulb.)

If the neck of the onion is stiff and still rigid, it is not ready to harvest. Leave those onions to continue growing. When they’re ready, the necks will turn white and bend flat, crimping over.

By watching these signs, I pick my onions at the best time. Some types of onions will mature sooner than others. Our Utah Yellow Spanish onions are often ready to harvest first.

Pro-Tip: Waiting for the onion to be ready before harvesting will increase your long term storage success. When the neck dries up, it prevents moisture from getting into the onion causing spoilage.

How to Harvest Onions

Harvest your onions by grasping the onion bulb and pulling it out of the soil. If you try to pull them up from the tops, you may break the neck of the onion.

Preparing Onions For Storage

Curing onions before storing them enhances the flavor by concentrating the sugars and aromas. Curing also helps onions last longer, reducing moisture and preventing rot.

The curing process dries the outer skin and makes them ready for long term storage. There is a specific way to cure your onions so that they last for months!

Pro-Tip: It is important to mention that not all varieties of onions make a good storage onion. Certain varieties are known for their superior storage shelf life while others should be consumed soon after harvesting. Make sure you choose good storage onions for planting if that is what you plan to use them for.

Follow these step-by-step instructions to properly cure your onions.

Materials Needed to Prep Onions for Storage

• Pruning Shears or Kitchen Scissors - Grab hand pruners or sharp scissors for trimming your onions.

• Drying Rack - You can use whatever you have handy as a drying rack as long as it will allow good air circulation around all of your onions. (Baking cooling racks, wooden crates, and large screens work well.)

• Wheelbarrow - A wheelbarrow is not essential, but it is handy to toss the tops and roots in to take them to the compost pile.

How to Cure Onions

1. Harvest - Harvest your onions on a sunny, dry day.

2. Clean the Onions - Gently brush off the bulk of the dirt with your hands. You don’t need to get all the dirt off and you don’t want to scrub them, but you want to remove large amounts of dirt that would hold moisture against the onion.

3. Trim the Tops - Trim the greens off of the tops of the onions leaving about 1 - 2 inches of the neck.

4. Trim the Roots - Also trim off the roots like you are giving them a short haircut, leaving a little stubble of roots.

5. Compost the Tops - Toss the tops and roots into a wheelbarrow and later dump the wheelbarrow into your compost pile. Composting onion tops will help reduce pests in your compost pile and organic garden. Pro-Tip: Once the onion tops topple in the fall, they tend to lose flavor, become wilted, yellow, and woody. For that reason, we only save the best onion tops for eating when we harvest our onions; the rest go into the compost pile.

6. Dry the Onions - Find a warm, dry, well-ventilated location for your drying rack. Place the onions on the rack in a single layer with air circulating between each one. Let them sit for 1 to 2 weeks before storing them.

How to Store Onions

After curing, I store them in a mesh bag, hanging basket, crate or other breathable container. The ideal storage conditions are cool, dry, and well ventilated.

Remove any soft or damaged ones to keep the rest fresh. The best temperature for storing onions is 33 to 40°F.

Now that your onions are cured and stored, you can enjoy them in all your favorite dishes!