How To Actually Tell if an Onion Has Gone Bad

How To Actually Tell if an Onion Has Gone Bad

A skilled farmer must have a keen eye when spotting a good or bad vegetable. There are certain signs to consider for onions when determining how good the vegetable is. Read on to learn how to determine when an onion goes bad and pick the best crops for the next farmer’s market.

What Defines a Good Onion?

Although the smell and taste of onions make many cry, they’re a great vegetable. You’ll know you have a good onion when you see the skin has a balanced color with few blemishes. The skins will have a slight shine and a crisp texture that isn’t too dry.

Cut open an onion and smell it to notice the slightly sweet scent that it emits. The fumes may make you cry due to the amino acids that irritate the eyes, but the smell is quite appetizing. Fresh onions won’t have as strong a smell but will have a great taste that teeters between sweet and tangy.

It’s just as important to identify good onions as it is bad ones when harvesting to ensure you have the best batch for the farmer’s market. Consider these good signs, and the bad signs will become easier to spot.

Physical Signs

Like any vegetable or fruit, onions will have physical signs of spoilage that come in different forms. Knowing these physical signs will help you immediately identify if an onion is close to going bad or already spoiled.


Dark spots will appear on an onion’s surface when it begins to spoil. These spots are mold that typically grow post-harvest due to unsuitable temperatures. The mold will dust off the onion’s outer skin in small amounts, making it difficult to identify a bad onion in the harvested patch.

Handle onions carefully and prevent them from getting wet; visibly seeing the mold will prevent you from mistakingly adding it to this year’s produce for sale. Larger concentrations of black mold will appear as larger spots or lines on the onion’s surface and underneath its skin. These spots are more prominent and mean the onion has remained in poor temperatures for too long.


If you notice a growth or a small sprout in your onion, it means the onion has too much moisture surrounding it. Moisture will ruin onions and cause them to mold, but the moisture may also result in the onion sprouting a new plant. Many farmers will rely on this growth to continuously grow onion crops.

However, since the onion isn’t in the ground while it’s moist, it will most likely go bad. Keeping onions dry will keep them in good condition for the farmer’s market and help you sell the best vegetables. Feel around the onion for any lumps or uneven surfaces, and look for any bumps indicating a sprout.

Soft Texture

Since onions typically have a harder texture, a soft onion is a physical sign of spoilage. As previously mentioned, moisture causes onions to go bad, and aside from the presence of mold and sprouts, the softness is a clear indication of a bad onion.

Give onions a strong squeeze when you harvest them to check their firmness. The onion should have the smallest indent when you loosen your grip where your fingers were but should maintain a smooth appearance overall.

A soft onion will release juice upon squeezing, and the surface will appear slimy. Firmness means better health; testing its durability is essential to knowing if your onions have gone bad.


Even if the physical signs aren’t obvious, the onion’s smell will help you determine if it’s bad. The slightly sweet smell of a good onion becomes replaced by an acrid, sour odor when it goes bad. Spoilage affects multiple senses to alert someone that the food is dangerous to their health.

The odor emitted from an onion is another sign to pay attention to when finding good onions in the patch. Smell your onions whenever you handle them to ensure they’re ready for the farmer’s market. If you smell the pungent odor of the vegetable, then so will your customers.

The Worst Environment for An Onion

Onions require specific environments to ensure they remain fresh for as long as possible. Avoid keeping onions in the sun, as the heat will cause them to soften and spoil.

Muggy or damp environments will guarantee that your onions will go bad and grow a plant. Onions are delicate vegetables and require various settings, but once you have the right ratios, they will remain in great shape.

Prolonging the Life of an Onion

Just as there are ways to cause it to spoil, there are settings where onions will thrive. Keep your onions in a cool, dry place to avoid the previously mentioned effects. Darkness is necessary to ensure onions don’t spoil, which is why people keep harvested onions out of the daylight.

The best place to store onions is in a basement or cellar, where the environment is dark, and the air is dry.  Make sure onions have great ventilation to avoid moisture build-up using mesh onion storage bags that give the vegetable room to breathe. 

The Effects of Bad Onions

A bad onion has unfortunate effects on the others stored with it. Misidentifying and placing a bad onion with the good ones reduces the harvest and gives you less food to sell. A soft onion will release more juice and dampen the others, causing a chain of spoilage.

Black mold will spread to other onions and cause them to mold, especially in warm environments that encourage mold growth. Inspect onions to avoid wasted produce. Your judgment is a valuable part of the harvesting process, and you’ll need to throw away anything that could harm the rest of the onions.

Use Rotten Onions for Composting

Don’t let your bad onions go to waste. Compost any you find to provide nutrients to the other crops.

Composting rotten onions is an excellent way to ensure your hard work pays off as you nourish the other crops. Onions typically need organic matter in their soil to grow well, making composted onions an excellent way to create a growth cycle.

Your onions are valuable products to sell at farmer’s markets, but there might be the occasional bad onion you need to remove. Remember these signs to know when an onion goes bad, and harvest the best crop of this unique-tasting food.

How To Actually Tell if an Onion Has Gone Bad