Why Are My Potatoes Green? (And Are They Safe?)

Green potatoes mean one thing: light. When a potato is exposed to light it produces chlorophyll (the green pigment) and, alongside it, a natural toxin called solanine. Do not eat the green parts — they are bitter and not safe.

Why potatoes go green

A potato is a tuber that grows underground, in the dark. The moment light reaches it, two things happen at once:

• It makes chlorophyll, which turns the skin and flesh green.
• It makes more solanine, a bitter, toxic compound the plant uses for defence.

The green colour is harmless in itself — it's just the visible signal that solanine has built up. The two go together, so green skin is a reliable warning sign.

Light reaches your potatoes in two common ways:

1. In the ground. Tubers that form near the surface, or get pushed up as the plant grows, poke into the light. This is by far the most common cause in UK gardens.
2. In storage. Potatoes left in a daylit kitchen, a clear bag, or on a sunny windowsill will green up over days or weeks.

Are they safe to eat?

No — not the green parts. Solanine is genuinely toxic in quantity, and it tastes harsh and bitter, so a heavily green potato is unpleasant as well as unwise. Cooking does not destroy it.

Here's the practical rule:

• Small green patch? Cut it away generously — take off the green plus a good margin of the flesh underneath. The rest of the tuber is fine.
• Mostly green, or green right through? Throw it away. It isn't worth the risk.
• Bitter taste when cooked? Spit it out and bin the lot. Bitterness is solanine talking.

How to prevent it

Prevention is all about keeping the tubers in the dark — in the ground and afterwards.

Earth up as they grow. This is the big one. Drawing soil up around the stems keeps developing tubers buried and blocks the light. Do it as the plants reach about 20cm and again a few weeks later. See our full guide to earthing up potatoes for how and when.

Plant deep enough. Set seed potatoes around 12–15cm deep so the tubers form well below the surface. Shallow planting means more greening later. The potato guide covers planting depth and spacing.

Cover any that surface. If you spot tubers peeping out of the soil mid-season, simply pull more soil or a thick mulch over them straight away.

Growing in bags or containers? Top up with compost as the foliage grows, just as you would earth up in the ground — the same light-blocking job. Our growing food in containers guide explains the method.

Store them in the dark. After lifting, keep potatoes somewhere cool, dry and completely dark — a paper or hessian sack in a shed, garage or cupboard is ideal. Never store them in clear plastic or in a lit room.

A few green potatoes aren't a disaster — trim them, fix your earthing up, and your next batch will be fine. For everything else, head back to the potato guide or browse more problem-solving guides.