How to tell if potatoes are bad

Potatoes are fairly easy to grow, but the tubers that are produced are sensitive. They can go bad fast in certain conditions, or they can last about a year when conditions are just right. There is also a difference between raw and cooked as far as spoilage.

A potato is bad if there are bruises, blemishes, dark spots, or if the skin is wrinkled, or the potato feels mushy or smells bad. Ideally, a potato should feel firm, have smooth skin, & have no sprouts. Green potatoes contain solanine, a toxin that in larger amounts can cause paralysis.

If a potato has sprouted, that means it will go bad very soon. Sprouts should not be eaten, but it is still OK to eat the potato after the sprout has been cut away.Potatoes do have a distinct smell, so an odor in itself is not a problem.

How to tell if potatoes are bad?

If a potato feels soft or mushy, it is probably bad.

To some extent, it depends on how much it bothers you.

A little softness means it is going bad in a hurry, but whether it can still be eaten depends on your own taste.

The same is true for cooked potatoes.

To some extent, it is a matter of how much it bothers you but cooked potatoes do not last very long.

Potatoes that feel mushy or soft, or have some big spots, are likely bad & should be thrown out. Sprouting is a sign that the tuber is ready to start growing new plants. Cooked potatoes should not smell rotten or moldy, and should not be squishy.

Potatoes are very healthy food and they are a staple for many.

They can go bad easily, and it is not good to eat them after some point.

They also have very thin skin and can be damaged easily, which makes them deteriorate even faster.  

Spoiled potatoes undergo chemical changes that make them not good for you.

Cooked potatoes can spoil in just a few days and they are a risk of spreading bacteria. 

See our complete guide to growing healthy potatoes.

How to tell if a sweet potato is bad

For any type of root plant, firmness is the key to telling whether it is fresh.

Sweet potatoes tend to feel even firmer than regular potatoes when they are in good shape.

Sweet potatoes can often last longer than regular potatoes as well.

Sweet potatoes often last longer than regular potatoes, but if they are shriveled, have spots, or have blemishes, dark spots, or other damage, they should not be eaten. Sweet potatoes that are bad will have an obvious rotten or moldy smell..

The surface mold is a problem, but you can cut it away and the potato will be safe to eat.

If they have large white or green spots, that is mold, and they should be thrown out. 

If they develop black spots, the tubers will taste bitter. 

See our full guide on how to grow sweet potatoes.

How to tell if green potatoes are bad

Potatoes can turn green, and unlike most other vegetables, this is not a good thing.

They can turn green if not stored properly, and are exposed to too much light.

The green is due to chlorophyll, and it develops chemicals that can be harmful to humans.

Potatoes that have small amounts of green are OK to eat. However, if the potato is mostly green, then it should not be eaten, since green potatoes have solanine, which is a digestive irritant, & can cause health problems in small children. The green color is a result of exposure to light.

If a potato is mostly green it should be thrown out.

If there is only a little, you can cut that part off.

If the potato tastes bitter, that means they likely have developed solanine, which is poisonous to humans.

You can still use a green potato, and plant the sprout that eventually shows up. 

If the green is small enough, it can be cut away. If the rest of the potato tastes OK, it is fine to eat.

A bitter taste is the taste of dangerous chemicals that have developed.

See the most common potato pests & how to get rid of them.

Are sprouted potatoes bad?

Potatoes that have grown sprouts are not bad, yet, but they will be soon.

They are still safe to eat as long as you remove the sprouts.

Do not eat the sprouts because they have solanine and other toxic glycoalkaloids that are harmful to humans.

Sprouted potatoes are OK to eat; simply cut the sprouts off. The flesh of the potato will start to feel soft after the potato sprouts, so sprouting potatoes should be eaten as soon as possible. Green potatoes contain solanine, which is a digestive irritant, & can be poisonous in larger quantities.

 A potato will sprout as part of its aging process.

The sprout is starting a new plant that could come up the following year if it is not pulled out of the ground. 

How long do potatoes last?

Potatoes can last a long time if stored properly. In some cultures, the potato is the staple food item that is eaten often.

They grow enough to keep them through the winter until the next planting season.

In ideal conditions, potatoes can last for several months. Ideally, potatoes should be stored at a cool temperature (42 – 50°F), in darkness, with high humidity (around 90 -95% relative humidity). At room temperature, potatoes last a few weeks. Cooked potatoes are good for 3 – 4 days.

The key to keeping potatoes usable is proper storage.

They like a cool dry place without much light once they are mature and out of the ground.

It is possible to freeze cooked potatoes in some cases.

Check out this article for more tips on keeping your potatoes from going bad.

What happens if you eat bad potatoes?

Bad potatoes do not taste good, and that is the least bad thing that can happen.

Poison can develop when potatoes turn green, and in the sprout itself.

Bad potatoes should not be eaten.

In a worst-case scenario, the chemical solanine contained in green potatoes can cause paralysis, or at least make you very sick (vomiting, diarrhea); the same is true for sprouts & potato greens. Cooked potatoes that have gone bad contain bacteria which can also make you sick.

Bad potatoes should not be eaten.

At a minimum, they will taste bad and upset your stomach.

At worst, they could make you extremely ill.

Can you eat green potatoes?

All vegetables have chlorophyll, which is what makes them green.

That’s a good thing for most plants, but it is not a good thing for tubers like potatoes.

When potatoes turn green–which indicates the potato has produced chlorophyll–the potato has also produced solanine, which is a digestive irritant and can be poisonous in larger quantities..

Green potatoes can be eaten if only small parts are green & they’re removed before eating. Potatoes that are mostly green contain solanine, which in small quantities is a digestive irritant. In larger quantities–or for small children–solanine can be poisonous.

So, you should not eat green potatoes.

If there is only a small part that is green, you can cut that part off and eat the rest.

After cutting away the green taste, the potato.

If it tastes bitter, it has developed toxins and should not be eaten.

It is too much light that causes potatoes to turn green.

That means it is very likely that toxic chemicals have developed, and those can make you sick.

Maybe the best thing to do with green potatoes is to plant them–that way, you’ll have a crop of healthy potatoes later on.

Check out our guide to planting potatoes.

Are potatoes with sprouts safe to eat?

Potatoes are tubers or root plants. In nature, they reproduce themselves.

The roots, which are potatoes, store excess nutrients and eventually start growing sprouts.

That will start a new potato plant.

Sprouted potatoes can be safe to eat if you trim off the sprout & its surrounding area with a paring knife. If the potato is mostly green though, solanine is present; solanine is a digestive irritant, & in larger quantities or for small children, is poisonous–even causing paralysis.

Sprouts of potatoes are not safe to eat.

Sprouts contain solanine, which is toxic. 

Solanine causes digestive irritation, and in larger quantities–or for small children–can cause vomiting & even paralysis.

Sprouts are not safe to eat.

A sprouting potato is about to go bad, but may not be bad yet.

If the potato still feels firm, you can cut the sprouts away and eat what is left without a problem.

It’s best to plant sprouted potatoes.

That way, you’ll grow your own crop of spuds!

Check out our how-to guide for planting potatoes.

About the author

Greg Volente

Greg Volente holds a Naturalist Certificate from the Morton Arboretum, worked for The Nature Conservancy leading environmental education programs and doing natural areas restoration, and worked in the soil science research & testing lab at Michigan State University. Besides gardening, he's an avid wildflower enthusiast, and loves botanizing, hiking, and backpacking.