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

Green potatoes in the UK — why they turn green, why the green parts are not safe to eat, and how earthing up stops it happening.

By The Farm Simple Team4 min read
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Part of: How to Grow Potatoes in Bags and Beds

Freshly harvested potatoes
Photo: Ordercrazy (CC0) via Wikimedia Commons

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The short version

  • Cause — light hits the tuber, triggering green chlorophyll and the toxin solanine.
  • Not safe — never eat the green parts; cooking doesn't destroy solanine, and bitterness means bin it.
  • Small patch — cut the green plus a margin of flesh away generously; the rest is fine.
  • Main fix — earth up as plants reach about 20cm (and again later) to keep tubers buried.
  • Also — plant 12–15cm deep, cover any tubers that surface, and store somewhere cool, dry and completely dark.

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.

It's light, not sun specifically

Ordinary daylight and even indoor lighting will turn potatoes green over time. They don't need direct sunshine — any light at all does it.

Light turns potatoes green, in the ground or in store

Light turns potatoes green, in the ground or in storeOn the left, a potato plant on a ridge of soil. One potato pokes out of the side of the ridge into the sun and turns green, and a dashed outline shows the soil that should cover it. The seed potato sits deep below. On the right, potatoes in a clear bag on a sunny windowsill have turned green, while a paper sack of potatoes sits in a dark cupboard.In the groundIn daylightIn the dark12345
  1. A tuber that forms near the surface, or gets pushed up as the plant grows, pokes into the light. It makes green chlorophyll and, with it, more solanine, a bitter, toxic compound. This is the most common cause in UK gardens.
  2. Earth up as the plants reach about 20cm and again a few weeks later, and pull more soil or a thick mulch over any tubers that surface, straight away.
  3. Plant seed potatoes around 12–15cm deep, so the new tubers form well below the surface.
  4. Stored potatoes green up too: in a daylit kitchen, in a clear bag or on a sunny windowsill. Any light does it, not only direct sun.
  5. Store them somewhere cool, dry and completely dark, in a paper or hessian sack in a shed, garage or cupboard.

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.

When in doubt, throw it out

Green potatoes are not safe for people, pets or chickens. If a potato is significantly green or tastes bitter, compost or bin it rather than eat it.

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.

Curing helps storage

Let lifted maincrop potatoes dry for a few hours, then store unwashed in the dark. Damp, washed potatoes rot faster — and a dark store stops greening at the same time.

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.

Frequently asked questions

Are green potatoes safe to eat?
No — green potatoes contain solanine, which is toxic and tastes bitter. Cut away small green patches generously, and throw away any potato that is mostly green.
Why do potatoes turn green?
They turn green when exposed to light, which triggers chlorophyll and the toxin solanine. It happens to tubers near the surface or stored in the light.

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Freshly harvested potatoes
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