Before going on the holidays I dug up some volunteer tatties,washed them and left on colander on the worktop.I came back from the holidays and they turned green.
The same with bought tatties-turned green.

I heard they are poisonous but I ate them and I'm fine(and so is OH)

So...is that another myth or am I immune to green tattie poison?

You are lucky not to have had stomach upsets. I think you would need to eat a lot to suffer fatal consequences (but I'm not a doctor).

Potatoes turn green when exposed to the light, this is the purpose of earthing up, to prevent light getting to tubers near the surface. It's true that the green bits are poisonous, and even once you take the green bits off, the rest of the tuber contains traces of the poisonous stuff. As potatoes are related to deadly nightshade, it's best not to take too many risks

Really not to be recommended, C:
"Potato poisoning is rare, but it does happen from time to time. Death normally comes after a period of weakness and confusion, followed by a coma. The majority of cases of death by potato in the last fifty years in the USA have been the result of eating green potatoes or drinking potato leaf tea."
Top 10 Poisonous Foods We Love To Eat - Listverse
b.

Potatoes turn green if left exposed to light Coreopsis. They are poisonous and taste horrible. You may have escaped poisoning on this occasion but they are very highly implicated in foetal defects. Hope no one is pregnant. Please don't eat green potatoes again.

I'm just curious-how something perfectly edible left on the worktop for about 10 days may turn into something poisonous???

...All potatoes contain substances known as glycoalkaloids. The most common in potatoes are solanine and chaconine. Light reacts with these substances to turn potato flesh green. The green parts of a potato are a guide to where these substances tend to accumulate which is just below the potato skin. Ingested in large quantities these toxic compounds could lead to coma or even death. In smaller quantities the most likely effects are diarrhoea, headaches and stomach cramps. Fortunately these toxic substances are eliminated by thorough cooking. Solanine is the toxic substance found in deadly nightshade which indicates the potential seriousness of eating uncooked potatoes which are, in any case, hard to digest and unpleasantly flavoured. The only recent cases of solanine poisoning lined to potatoes have been the result of drinking potato leaf tea or green potatoes. When potatoes turn green it is an indication of higher concentrations of solanine...

Raw potatoes aren't good for you either, green or otherwise.

All potatoes that you intend to eat should be kept in the dark to prevent them from turning green, and any green ones should be discarded and (obviously) should definitely not be fed to children!

Poison......

Originally Posted by coreopsis

I'm just curious-how something perfectly edible left on the worktop for about 10 days may turn into something poisonous???

C, you're straying (hopefully in not too confused a state caused by eating green potatoes) into the complex area of food chemistry, oxidation etc and food scientists can tend, of necessity, to talk their own language and equations. The unlikely sounding FAIA (Food Additives and Ingredients Association) do try to explain some of this chemistry in understandable terms for the non-chemist and might at least offer a glimpse into some of the complexities - e.g. their booklet at
http://www.faia.org.uk/booklet.pdf
b.

But I think green potatoes can be used as seed potatoes - that it's OK to plant them.

Is that right? I hope so, I've a few sitting on the windowsill for Christmas spud planting.

Get plenty of loo roll in if you try it again.

I would most certainly not recommend a pregnant woman eating green spuds even if the green bit has been cut away.
I think if there's a trace of green the potatoes taste bitter.

Originally Posted by maytreefrannie

But I think green potatoes can be used as seed potatoes - that it's OK to plant them.

Is that right? I hope so, I've a few sitting on the windowsill for Christmas spud planting.

You don't eat the green potatoes though - they end up all mushy and horrid.

You can plant green potatoes as seed. Nothing wrong with that. They just shoot the genes out, you don't eat the seed potato lmao!

Originally Posted by coreopsis

I'm just curious-how something perfectly edible left on the worktop for about 10 days may turn into something poisonous???

Because potatoes need to be stored in the dark!! It's daylight that turns them green. Some sort of chemical reaction.