How to Tell If a Potato Is Bad: 7 Clear Warning Signs

If your potato has soft spots, mold, green patches, or a foul odor, it's gone bad and should be discarded. Potatoes with significant sprouting, wrinkling, or mushy texture are also unsafe to eat. When in doubt, throw it out to avoid potential foodborne illness.

Spot the Signs: Your Complete Guide to Identifying Bad Potatoes

Potatoes are kitchen staples, but they don't last forever. Knowing exactly how to tell if a potato is bad can save you from food poisoning and wasted meals. This guide gives you the practical knowledge to confidently assess potato freshness every time you reach into your pantry.

Visual Indicators That Signal Spoilage

Your eyes are the first line of defense against bad potatoes. Here's what to look for:

Condition	Appearance	Action Required
Green patches	Areas turned green from light exposure	Peel deeply or discard if extensive
Mold growth	Fuzzy spots in white, green, or black	Discard entire potato immediately
Significant sprouting	Long sprouts emerging from eyes	Discard if sprouts exceed 1 inch
Wrinkling	Shriveled, leathery skin	Discard if accompanied by soft spots

According to the USDA Food Safety and Inspection Service, green discoloration indicates the presence of solanine, a natural toxin that can cause nausea and headaches when consumed in significant quantities. While small green spots can be cut away, extensive greening means the entire potato should be discarded.

Sensory Clues You Can't Ignore

Beyond visual inspection, your other senses provide critical information:

• Smell test: Fresh potatoes have an earthy, clean scent. A musty, moldy, or sour odor indicates bacterial growth and spoilage.
• Texture check: Gently squeeze the potato. It should feel firm throughout. Soft spots, mushiness, or sponginess means internal decay has begun.
• Surface examination: Run your fingers over the skin. Slimy or sticky residue is a clear sign of bacterial growth and means immediate disposal.

Understanding the Potato Spoilage Timeline

Potatoes don't go bad overnight. Understanding the progression helps you catch problems early:

1. Days 1-7: Ideal storage conditions maintain freshness with minimal changes
2. Weeks 2-3: Initial sprouting may appear; potatoes remain safe if firm
3. Weeks 4-6: Significant sprouting, possible slight softening at ends
4. Weeks 6-8: Noticeable wrinkling, soft spots developing
5. 8+ weeks: Advanced spoilage with mold, extensive softening, or foul odors

The FDA Food Code notes that proper storage dramatically affects this timeline. Potatoes stored in cool, dark, well-ventilated conditions last significantly longer than those kept in warm, humid environments.

When Is a Sprouted Potato Still Safe?

Many home cooks wonder if they can salvage sprouted potatoes. The answer depends on multiple factors:

• Small sprouts (under 1 inch) with firm texture: Peel deeply around sprouts and eyes, then use immediately
• Long sprouts with soft spots: Discard the entire potato
• Sprouts accompanied by green skin: Discard due to potential solanine concentration

Research from the University of Illinois Extension confirms that while sprouting itself isn't dangerous, it indicates the potato is using its energy reserves, leading to texture and flavor degradation. More importantly, sprouting often coincides with increased solanine production, particularly when combined with green discoloration.

Proper Storage Techniques to Maximize Freshness

Prevention beats detection. Follow these science-backed storage methods:

• Store in a cool, dark place between 45-50°F (7-10°C)
• Use breathable containers like paper bags or mesh sacks
• Keep away from onions, which release gases that accelerate sprouting
• Never refrigerate raw potatoes (causes sweetening and texture changes)
• Check stored potatoes weekly and remove any showing early spoilage signs

Safety First: When to Definitely Discard Potatoes

Certain conditions mean immediate disposal is necessary:

• Any visible mold growth (don't attempt to cut away)
• Strong unpleasant odors
• Multiple soft or mushy areas
• Extensive green discoloration
• Slippery or slimy surface texture

The Centers for Disease Control and Prevention reports that improperly stored potatoes can harbor Clostridium botulinum spores, which cause botulism in rare cases. When potatoes become overly moist and are stored in anaerobic conditions (like sealed plastic bags), these dangerous bacteria can proliferate.

Extending Potato Shelf Life: Practical Tips

Maximize your potato investment with these professional techniques:

• Store potatoes with an apple to reduce sprouting (apples release ethylene gas)
• Keep potatoes dry—never wash before storage as moisture accelerates decay
• Rotate your stock using the "first in, first out" principle
• Inspect potatoes before purchasing to avoid bringing compromised ones home
• Consider variety differences—russets typically last longer than fingerlings

Common Potato Myths Debunked

Let's address some widespread misconceptions:

• Myth: "Green spots are just chlorophyll and harmless" Fact: Green indicates solanine production, a toxic compound
• Myth: "You can remove all toxins by peeling deeply" Fact: Solanine penetrates deep into the flesh—extensive greening requires full disposal
• Myth: "Refrigeration extends potato shelf life" Fact: Cold temperatures convert starch to sugar, altering taste and cooking properties

What to Do With Slightly Imperfect Potatoes

Potatoes showing early signs of aging but still firm can often be rescued:

• Make roasted potatoes immediately—high heat destroys some surface bacteria
• Peel deeply to remove any questionable areas
• Use in soups or stews where texture matters less
• Consider making potato pancakes to use up smaller quantities

Remember that food safety should always come before waste prevention. The USDA estimates that foodborne illnesses cost Americans billions annually—don't risk your health to save a few dollars on produce.

FAQ: Frequently Asked Questions

Can you eat potatoes with small sprouts?

Yes, if the potato remains firm and sprouts are small (under 1 inch). Remove sprouts and eyes completely by cutting deeply, then use immediately. Discard if sprouts are long or accompanied by soft spots or green skin.

Why do potatoes turn green and is it dangerous?

Potatoes turn green when exposed to light, which triggers chlorophyll production and the formation of solanine, a natural toxin. While small green spots can be cut away, extensive greening means the entire potato should be discarded as solanine isn't destroyed by cooking and can cause nausea, headaches, and digestive issues.

How long do potatoes last in storage?

Properly stored potatoes last 2-3 months in ideal conditions (45-50°F, dark, well-ventilated). At room temperature, they typically last 1-2 weeks. Refrigeration isn't recommended as it converts starch to sugar. Always check weekly and remove any showing early spoilage signs to prevent contamination of the entire batch.

What's the difference between bad potatoes and normal aging?

Normal aging includes slight sprouting and minimal wrinkling while maintaining firm texture. Bad potatoes show multiple warning signs: soft spots, mold, strong odors, slimy texture, or extensive greening. When multiple negative indicators appear together, the potato has spoiled and should be discarded immediately.

Can cooking destroy potato toxins?

No, common cooking methods don't destroy solanine, the toxic compound that develops in green potatoes. Boiling, baking, or frying may reduce some surface bacteria but won't eliminate this heat-stable toxin. The only safe approach is to discard potatoes with significant greening or other advanced spoilage signs.