You’re about to make a baked potato, mash potatoes for dinner, or slice one for roasting — and suddenly you notice a strange black ring or dark spot inside.

At first glance, it looks alarming. Is the potato rotten? Moldy? Unsafe to eat?

Thankfully, in most cases, the answer is much less dramatic.

Those dark rings are usually a harmless condition known as internal black spot or internal bruising, and they’re surprisingly common.

What Is the Black Ring in a Potato?

The black or darkened area inside a potato is often caused by damage or stress during storage and handling.

Unlike mold or rot, these spots are usually:

• Dry, not slimy
• Dark gray, black, or slightly purple
• Firm rather than mushy
• Hidden inside while the outside looks normal

That’s why you often don’t notice anything unusual until you cut the potato open.

Why Does It Happen?

There are several common reasons potatoes develop dark rings or spots inside.

1. Pressure Bruising

Potatoes may look tough, but they bruise more easily than most people realize.

When potatoes are:

• Dropped
• Stacked too tightly
• Bumped during transport
• Stored under heavy weight

…the inside tissue can become damaged.

This bruising doesn’t always show on the skin, but it may appear later as black spots or rings inside the potato.

This is one of the most common causes.

2. Low Oxygen During Storage

Potatoes need proper airflow during storage.

If they’re kept in conditions with poor ventilation, the center can darken because the potato tissue isn’t getting enough oxygen.

A more severe version of this is called blackheart, where the middle turns almost completely black.

The ring-shaped spots are usually a milder version of this issue.

3. Temperature Stress

Potatoes are sensitive to temperature changes.

Storing them:

• In the refrigerator
• In very cold environments
• Near heat sources
• In places with fluctuating temperatures

…can disrupt their internal chemistry.

Cold temperatures especially can convert potato starch into sugar, which may contribute to discoloration and dark spots.

4. Natural Oxidation

Sometimes the dark rings are simply caused by oxidation.

Inside every potato is vascular tissue — tiny “veins” that transport nutrients.

When exposed to air or stress, these tissues can naturally darken over time.

This process is harmless and similar to how apples brown after being cut.

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