How To
Harvesting onions at the right time ensures you get perfect, flavorful bulbs that store well—so timing and technique matter more than you might think.
Picture this: you’ve spent weeks tending to your 🧅 crop, only to pull a bulb that’s either too small or already sprouting. That’s the difference between a rewarding harvest and wasted effort.
Knowing when your onions are ready—whether by checking the tops for yellowing or using the soil pull test—is the key to avoiding common mistakes. Below, I’ll walk you through the exact signs to watch for, plus how to handle them once they’re out of the ground.
From regional climate tips to storage tricks, you’ll learn everything to turn your harvest into a pantry staple that lasts all winter.
How to test onion readiness: the soil pull method explained
The soil pull method is my go-to technique for determining when onions are ready to harvest—whether you're growing storage onions or green onions. This simple test helps you avoid overmature bulbs that become pungent or split. The key is checking the bulb size and root development without damaging the plant.
Start testing about 100-120 days after planting, depending on your onion variety. For short-day onions, this might be earlier (around 90 days), while long-day varieties often need the full 120-150 days.
The soil pull test works best on dry, sunny days when the soil is loose and easy to work with.
Step-by-Step Soil Pull Test for Onions
- 1 Choose a sunny, dry day to minimize soil disturbance. Avoid testing after heavy rain when the soil is too wet.
- 2 Gently loosen the soil around one onion plant using your fingers or a small trowel. Work carefully to avoid damaging the bulb.
- 3 Grasp the onion top and gently pull upward. If the bulb resists and roots come away easily, it's ready for harvest.
- 4 Check bulb size. A ready onion should be 2-3 inches in diameter with a firm, dry skin. If it's smaller than a golf ball, wait a few days.
- 5 Assess the neck. The stem should be shrinking and tightening near the bulb. If it's still thick, the onion needs more time.
- 6 Look for yellowing tops. When the green tops turn yellow and flop over, it’s a classic sign of readiness—but don’t wait until they’re completely brown.
If the bulb pulls out easily with a 2-3 inch diameter and firm skin, it’s time to harvest.
For green onions, you can pull them as soon as they reach your desired height (usually 6-12 inches tall), but the soil pull test still applies to check for root development.
Watch for overmaturity signs like wrinkled skin or tops that have completely collapsed. Overmature onions often split or develop hollow centers, ruining their storage potential. If you see these, harvest immediately—even if the bulbs aren’t perfectly sized.
For storage onions, aim to harvest before the first frost in your area. In USDA Zone 6a, this is typically by late October. If frost hits before your onions are ready, they’ll spoil in the ground.
In warmer climates, you may have a second harvest window in late winter or early spring.
Pro tip: Test a few onions from different parts of your garden. Soil consistency and sun exposure can vary, leading to uneven ripening. Harvest the earliest ones first to avoid overmaturity in the rest of the crop.
Once you’ve confirmed readiness, use a sharp knife or shears to cut the tops back to 1 inch above the bulb. This reduces moisture loss during curing and storage. Let them dry in a shady, well-ventilated area for 1-2 weeks before storing.
Mastering the soil pull test ensures you’ll always harvest onions at their peak—flavorful, firm, and perfect for storage. With practice, you’ll develop an eye for the ideal moment, turning your garden into a long-storing onion treasure trove. 🧅
Best harvesting techniques for onions: cutting, curing, and storage tips
Once you’ve confirmed your onions are ready to harvest—those yellowing tops and firm bulbs are key—proper post-harvest handling ensures sweet, long-lasting storage. Skipping these steps can lead to sprouting or moldy bulbs, so let’s dive into the best practices for cutting, curing, and storing your harvest.
The right techniques can extend your onions’ shelf life from weeks to months!
Start by gently pulling onions from the soil on a dry, sunny day to prevent rot. Use a garden fork to loosen stubborn roots, then brush away excess dirt. For storage onions, trim the foliage down to 1 inch above the bulb—this reduces moisture loss during curing.
Green onions, however, can be harvested whole or cut just above the soil line for regrowth.
⚠️ callout-warning ⚠️
⚠️ Critical Harvesting Mistake
Never harvest onions after a heavy rain—wet bulbs won’t cure properly and risk fungal growth. Aim for 3-5 days of dry weather before pulling to ensure successful curing.
✅ Pro Tip: Harvest in the morning when dew is low for the driest start.
After trimming, let onions cure in the sun for 2-3 hours to toughen the skins. Spread them in a single layer on a mesh screen or clean wooden rack, ensuring good air circulation.
Avoid direct sunlight for more than a few hours, as this can scorch the skins. For indoor curing, place them in a well-ventilated area with 60-70°F temperatures and low humidity.
Once fully cured—when the necks are dry and papery—store onions in a cool, dark place with high airflow, like a mesh bag or wooden crate.
Avoid plastic bags, which trap moisture and cause rot. Check bulbs monthly for sprouting or shriveling—discard any that develop mold or soft spots immediately to prevent spread.
For long-term storage, braid green onions and hang them in a dry, dark spot, or store them in the refrigerator’s crisper drawer for up to 2 weeks. Storage onions last 6-8 months under ideal conditions, but their flavor peaks in the first 3-4 months.
If you notice sprouting, use those onions first—they’ll be sweeter and more tender.
Troubleshooting common issues is half the battle. If your onions sprout prematurely, move them to the fridge to slow growth. For moldy bulbs, separate them immediately and discard the affected ones.
And if your stored onions shrink or become soft, they’ve lost too much moisture—try reviving them by placing them in a paper bag with an apple (the ethylene gas helps retain moisture).