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

A bad potato shows three critical warning signs: soft or mushy texture, extensive mold growth, and significant green discoloration. When potatoes develop these characteristics, they should be discarded immediately as they may contain harmful levels of solanine, a natural toxin that can cause food poisoning symptoms including nausea, headache, and vomiting.

Spotting Spoiled Potatoes Before They Make You Sick

Discovering spoiled potatoes after you've already started cooking can ruin your meal and potentially make you sick. Knowing exactly how to tell if a potato is bad saves you from food waste while protecting your health. This guide provides practical, science-backed methods to identify spoiled potatoes at every stage - from your grocery bag to your pantry.

Visual Inspection: What to Look For

Your eyes provide the first line of defense against bad potatoes. Examine each potato carefully under good lighting to catch these visual red flags:

• Green discoloration - Any green spots indicate solanine buildup from light exposure
• Mold growth - Fuzzy white, green, or black patches that spread quickly
• Excessive sprouting - Long sprouts (over 1 inch) with developed leaves
• Significant wrinkling - Deep wrinkles indicate advanced dehydration
• Dark spots - Large brown or black areas that penetrate beneath the skin

Texture Tells the Truth

Sometimes visual cues aren't enough. Your fingers provide crucial information about potato quality: Press test: Gently squeeze the potato. A fresh potato should feel firm throughout. Any soft spots, mushiness, or areas that yield easily to pressure indicate spoilage. Pay special attention to the ends and any areas near sprouts. Cut test: If you've cut into a potato and notice brown or gray discoloration inside that wasn't present before cutting, this indicates internal rot. The USDA Food Safety and Inspection Service confirms that internal discoloration often means the potato is no longer safe to eat (fsis.usda.gov).

When Smell Confirms Spoilage

Fresh potatoes have an earthy, slightly sweet aroma. As they spoil, their smell changes dramatically:

• Mildly spoiled potatoes develop a slightly sour or musty odor
• Severely spoiled potatoes emit a distinctly foul, rotten smell
• Moldy potatoes often have a damp, basement-like scent

If your potato smells unpleasant even before cooking, trust your nose - it's likely spoiled. The Cornell University Food Safety Lab notes that odor changes often precede visible spoilage in root vegetables (foodscience.cals.cornell.edu).

Understanding the Timeline of Potato Spoilage

Potatoes don't spoil overnight. Understanding their degradation timeline helps you catch problems early:

Time Period	Early Changes	Advanced Spoilage
0-7 days	Sprouts begin to form (small white bumps)	Small green spots appear from light exposure
1-2 weeks	Sprouts grow to 1/2 inch; slight softening at ends	Green areas expand; surface mold may appear
2-3 weeks	Noticeable wrinkling; sprouts reach 1 inch	Mushy spots develop; strong odor emerges
3+ weeks	Significant dehydration; multiple soft spots	Complete mushiness; extensive mold; unsafe to eat

When Is It Safe to Salvage a Potato?

Not all imperfect potatoes need immediate disposal. The FDA provides clear guidelines on when you can safely use potatoes with minor issues (fda.gov):

• Small sprouts (under 1/2 inch) - Cut away sprouts and the area beneath them
• Minor green spots (less than 10% of surface) - Peel deeply to remove all green tissue
• Small soft spots - Cut away affected area with generous margin

Discard immediately if:

• More than 25% shows green discoloration
• Mold covers multiple areas
• Potato feels completely soft or mushy
• It has a strong unpleasant odor

Proper Storage to Extend Potato Freshness

Preventing spoilage is better than detecting it. Follow these storage techniques to maximize your potatoes' shelf life:

• Cool, dark place - Store between 45-50°F (7-10°C), never in the refrigerator
• Air circulation - Use mesh bags or paper sacks, not plastic
• Separate from onions - Gases from onions accelerate potato sprouting
• Check regularly - Remove any spoiling potatoes to prevent spread

The University of California Cooperative Extension confirms that proper storage can extend potato freshness up to 2-3 months (ucanr.edu).

Health Risks of Eating Bad Potatoes

Consuming spoiled potatoes isn't just unpleasant - it can make you seriously ill. The primary concern is solanine, a natural toxin that increases as potatoes green or sprout. Symptoms of solanine poisoning include:

• Nausea and vomiting (within 10-12 hours of consumption)
• Headache and dizziness
• Abdominal pain and diarrhea
• In severe cases: fever, confusion, and difficulty breathing

The National Capital Poison Center warns that solanine isn't destroyed by cooking, so cutting away green parts is essential (poison.org).

Common Questions About Potato Spoilage

Can I eat potatoes with small sprouts?

Yes, if sprouts are small (under 1/2 inch). Cut away the sprouts and the area beneath them completely. The rest of the potato remains safe to eat if it feels firm and shows no other signs of spoilage.

Why do potatoes turn green and is it dangerous?

Potatoes turn green when exposed to light, which triggers solanine production. Green areas contain higher solanine levels - a natural toxin. While small green spots can be safely cut away, extensive greening means the entire potato should be discarded as solanine may have spread internally.

How long do potatoes last in the pantry?

Properly stored potatoes typically last 2-3 months in a cool, dark pantry. Warmer conditions accelerate sprouting and softening. Check weekly for any developing soft spots or sprouts, and remove affected potatoes immediately to prevent spoilage from spreading to others.

Can cooking destroy potato toxins?

No, solanine and other natural toxins in spoiled potatoes are heat-stable and cannot be destroyed by cooking. This is why cutting away green or sprouted areas before cooking is essential for safety. If spoilage is extensive, no amount of cooking makes the potato safe to eat.

What's the difference between mold on potatoes and harmless dirt?

Harmless dirt rubs off easily with water. Mold appears as fuzzy growth in white, green, or black colors that penetrates beneath the skin. If you see fuzzy patches that don't wash away, or if the area feels soft beneath the surface, it's mold and the potato should be discarded.