Tag: poisoning

Is sweet woodruff poisonous?

Posts about sweet woodruff are often accompanied by toxicity warnings and advice not to take it with warfarin or to check with your doctor first. So I thought an article on coumarins would be useful. 

Sweet woodruff contains natural compounds called coumarins – like many other plants, including strawberries, apricots, blackcurrants, tea as well as hay, sweet clover, bison grass, meadowsweet and tonka beans. In fact the highest concentrations in the food chain are found in cassia bark, one of the 4 species of commercial cinnamon. Coumarins have a lovely vanilla like scent and taste. Dried sweet woodruff infused into milk makes wonderful desserts. Sweet woodruff cheesecake, pannacotta, ice cream, custard, kulfi… and is also infused to make the traditional Maywein.


Unmodified coumarins do not affect the action of warfarin or similar anticoagulant, blood thinning drugs. This is because coumarins do not deplete vitamin K which affects the blood coagulation system. Modified coumarin – such as dicoumarol or coumadin – is different. Dicoumarol is synthesised and known as warfarin (Coumadin) and is used as a. rat poison. In nature coumarin can be modified by certain fungal infections which occur if the plants are are harvested while wet or damp. Sweet woodruff picked on a dry day and properly dried without any mould developing will not contain modified coumarins. 

Cancer risk

Coumarin is not classed as carcinogenic.

Liver toxicity

In 1954, the American FDA banned coumarin as a food flavour additive. This was largely based on the results of experiments with lab rats. However, rats process coumarin in their livers in a different way to humans. Rat livers metabolise coumarin into 3,4-coumarin epoxide which is highly toxic. Human livers metabolise coumarin into 7-hydroxycoumarin which is far less harmful. 

The lethal dose of coumarin has been has been calculated at 293 mg per kilo of body weight (taken orally in rat trials). So a dose of 20.51 grams for a 70kg adult. Cassia cinnamon – the highest food source of coumarin – contains 5.8 to 12.1 mg of coumarin per teaspoon of powdered bark. So you’d need to consume between 1,700 and 4,100 teaspoons of cassia cinnamon powder to reach a lethal dose. The German Federal Institute for Risk Assessment (BFR) calculated that a tolerable amount – if taken daily – is 0.1 mg/kg but sees no danger in higher amounts being consumed occasionally for a short time. For a 70 kg person that’s a tolerable daily dose of 7 mg – about half to one rounded teaspoonful of cassia cinnamon powder.  

Sweet woodruff has a fresh to dry weight ratio of around 10:1. The coumarin content ranges from undetectable to 0.6% (Chevallier, 1996) which would mean there are 6 grams of coumarin per kilo of woodruff. So you would need to consume 3.41 kilos of sweet woodruff to reach the lethal dose – about 34 salad bags full (based on a 100g supermarket salad). It’s a tiny delicate plant and 3.41 kilos would need some very dedicated harvesting! 

Given that you don’t need more than a couple of sprigs at a time – a handful at the very most – it appears almost impossible to kill yourself with sweet woodruff. However, if you steep a lot of it in alcohol and paint the town green, you may well give yourself one hell of a hangover!

Sweet Woodruff
Old herbalists called it Woodderowffe and it made a lovely children’s rhyme



Recited as

Double ewe double oh double dee ee, 
are-oh double ewe double eff ee.

The Mushrooms are Back!

Watching the tractors out mowing and baling in the fields fills me with dread, knowing that summer is drawing to a close and winter is on its way. So the appearance of the first mushrooms remind me that, in between is autumn with all its foodie delights! This Sunday morning was a treat. After a week (or two) of incessant rain, I woke up to a beautiful clear sunny morning, with just a hint of cool mist lying over the hill fields. I looked out of the window and there was only one thought in my head. Mushrooms!



I admit they have been on my mind for a week or two. Last weekend, walking in the Rumbling Gorge beech woods I could smell them. Tantalisingly I didn’t find a single one! But the woods smelled darkly, earthy, ‘mushroomy’ and I knew they were there. Little purple amethyst deceivers Laccaria amethystea lurking under the beech leaf humus. Many people don’t realise what amazing British mushrooms we have here, quietly getting on with life in the woods and fields. And many are edible mushrooms. Mushrooms are there all the time as they really live underground. They are made up of a wide spreading body called the mycelium which looks like thousands of tiny threads running through the soil. This mycelium is in the ground all year round and can live for decades. It spreads below the surface of the earth.

The mushrooms are the reproductive or fruiting bodies. They are often pushed up at stress points. E.g. If the mycelium reaches a road edge which prevents further underground expansion. Or if it has been very dry, then rains for a while. The mycelium then pushes up the mushroom. Under the mushroom caps are gills or pores. These can release millions of spores, which blow in the wind spreading mushroom “seeds” everywhere. This summer we have had several very dry months, followed by several unusually wet weeks in July and early August. My hope is that this will have given us the perfect mushroom season!



This morning I went down to some woods in Blairingone where I knew, from last year, that I could expect to find mushrooms. And there were certainly mushrooms there!

First, I found a young cep Boletus edulis also called porcini or penny bun. This cep alone made the morning worthwhile. It was unblemished. The flesh was white, close, firm and it had the most delicious smell. The cap had the typical bread bun finish and not a single slug or insect had had so much as a nibble.

These are one of the most delicious mushrooms you can find. Sliced thinly and fried for a few minutes in butter later that morning made the most perfect Sunday breakfast you can imagine.



Next I found some early chanterelles Cantharellus cibarius. They were hiding behind a dead gorse bush I remembered from a previous year. None were very big and only one or two were big enough to had developed their distinguishable wavy yellow edge. They were young and stubby. Nevertheless, the stems were thick, firm, nutty and peppery.

Near the beech leaf humus, in a spongy crop of moss, I also found a few purple amethyst deceivers Laccaria amethystea. They are such a pretty vivid velvet purple and one of the few mushrooms you can eat raw. Mixed with orange and yellow calendula petals they brighten up any salad! Then a few steps on, in a clearing between trees was a huge cep, alas too old and floppy to eat, next to a large but still passably firm bay bolete Boletus badius. Later on I chopped up the bolete (discarding the yellow-green pores as they were too spongy) and cooked it with the chanterelles and deceivers in butter, having added a spoonful of nasturtium seed capers from last autumn and a handful of chopped chives. Delicious!!

Lastly, I came across three lovely blushers Amanita rubescens. They are pinky-creamy white and have soft moveable scales on top. They have gills not pores. White, brittle, distinct gills. The stem is white going toward pinkish at the base. When bruised or cut they stain pink, hence the name the blusher. At the top of the stem is a white ring that falls down from the cap. On the upper surface you should find fine furrows texturing the surface. They also taste great! However, if you’re unsure how to identify these then don’t eat them – they have some nasty relatives! Oh, and peel them first to reduce the laxative effect!

Hedgehog fungus

Hedgehog fungus

Unsurprisingly, the only antidote to some mushroom poisoning is a herb. Specifically, milk thistle Carduus marianus. Various international research studies have found that milk thistle seeds contain a chemical constituent called silymarin. Silymarin has a protective, regenerative effect on the liver and protects the liver from the damage caused by various toxins, in particular the deadly liver toxins of the death cap mushroom Amanita phalloides. Milk thistle is currently popular among young Scottish binge drinkers who have discovered that a few milk thistle capsules the night before help you stay hangover free! Indeed, at Napiers it is one of the ingredients in our classic Hangover Hotchpotch.

I mention this only because it is useful for the serious mushroom forager to keep a stock of milk thistle tincture or capsules on hand. Prevention is better than poisoning. I always take great care when identifying new mushrooms I have found. But even then, a couple of milk thistle capsules before a mushroom feast always give me some extra peace of mind!

To see more of the British edible mushrooms I’ve eaten visit my Edible Mushrooms Pinterest board.