Potato mold typically appears as fuzzy patches on the skin that can be white, gray, green, blue, or even pink and orange depending on the type of fungus. Some mold stays on the surface, while other types penetrate deep into the flesh, causing sunken, wrinkled spots on the outside and brown or black decay inside. Knowing what you’re looking at helps you decide whether to toss the potato or salvage it.
Surface Mold: What You’ll See First
The most common mold you’ll spot on a potato is a fuzzy or dusty growth on the skin. It often starts near the eyes, cuts, or bruises where the skin is broken. White or gray fuzz is the most frequent, but you may also see blue-green patches similar to what grows on old bread. These surface molds thrive in warm, humid conditions and can appear on potatoes that have been sitting in your pantry for just a week or two if the environment is right.
What you see on the surface is only part of the story. Mold sends root-like threads deep into food, and those threads are invisible. In some cases, the toxins mold produces have already spread well beyond the fuzzy patch you can see.
Dry Rot: Sunken, Wrinkled Patches
Dry rot is one of the most common potato-specific molds, caused by a group of fungi that enter through wounds in the skin. It looks different from the fuzzy surface mold you might expect. The first sign is sunken, wrinkled patches on the potato’s surface that range from brown to black. The skin over these areas pulls inward and feels papery or shriveled compared to healthy skin nearby.
Cut open a potato with dry rot and you’ll find the internal tissue has turned brown, black, or sometimes a chalky white-orange color. The flesh is dry and crumbly rather than wet. In advanced cases, the inside develops cavities where the tissue has completely broken down. If the potato has been in storage for a long time, the wrinkled patches on the outside may sprout cottony masses of white, purple, pink, or brick-orange spores. At that point, the potato is well past saving.
Bacterial Rot Looks and Smells Different
Not all potato decay is mold. Bacterial soft rot is easy to confuse with fungal mold at first glance, but the differences become obvious quickly. Bacterial rot creates tan, water-soaked areas on the potato that feel slimy to the touch and may ooze liquid. The rotted tissue underneath turns white to cream colored and has a distinctly foul smell, sometimes compared to rotting garbage. Fungal mold, by contrast, tends to be dry and fuzzy without that strong odor.
If your potato is slimy, wet, and smells terrible, that’s bacterial decay rather than mold. Throw the whole thing away, and check any potatoes stored nearby since the bacteria spread easily through moisture.
Brown Spots That Aren’t Mold
Sometimes you cut open a potato and find brown or dark areas inside without any fuzzy growth on the outside. These aren’t always mold. Potatoes can develop internal discoloration from growing conditions alone. Brown center appears as a brown patch concentrated in the middle of the potato. Hollow heart creates an irregular cavity in the flesh surrounded by dark brown tissue. Heat necrosis shows up as scattered brown spots distributed randomly through the potato’s interior, often appearing inside the ring you see when you slice a potato crosswise.
These conditions are cosmetic rather than dangerous. You can cut out the discolored areas and eat the rest. The key difference: mold produces visible fuzzy or powdery growth somewhere (even if you need to look carefully), while physiological browning is just discolored flesh with a normal firm texture and no unusual smell.
When to Cut and When to Toss
Potatoes are dense, firm vegetables with relatively low moisture content, which works in your favor. The USDA considers potatoes a firm produce item, meaning small mold spots can be safely removed. Cut at least one inch around and below the mold spot, keeping your knife out of the mold itself so you don’t drag spores into clean flesh.
However, this only applies to small, isolated spots on an otherwise firm potato. If the potato has multiple moldy areas, large sunken patches of dry rot, any slimy or water-soaked texture, or a foul smell, discard the entire thing. The same goes if the potato has gone soft overall, since soft produce with high moisture content can harbor mold and bacteria throughout, even in areas that look clean. One important safety note: don’t sniff moldy food up close, as inhaling mold spores can trigger respiratory reactions.
How to Prevent Mold on Stored Potatoes
Potatoes store best at 45 to 55°F with high humidity around 90 to 95 percent. That’s cooler than most kitchens but warmer than a refrigerator (which converts potato starches to sugar and changes the taste). A basement, garage, or root cellar often hits the right range. Good airflow around the potatoes matters as much as temperature. Humidity keeps potatoes from shriveling, but any condensation on the skin creates the perfect environment for mold and bacterial growth.
Sort through your potatoes before storing them. Set aside any with cuts, bruises, or soft spots, and use those first. Damaged skin is the main entry point for mold, so even a small nick from harvesting or rough handling gives fungi a way in. Store potatoes in a breathable container like a paper bag, mesh bag, or cardboard box rather than sealed plastic, which traps moisture. Keep them away from onions, which release gases and moisture that speed up decay. In the right conditions, healthy potatoes can last several weeks to a few months without molding.