Wednesday Weed – Perforate St John’s-wort

Every Wednesday, I hope to find a new ‘weed’ to investigate. My only criterion will be that I will not have deliberately planted the subject of our inquiry. Who knows what we will find…..

Perforate St John's-wort (Hypericum perforatum)

Perforate St John’s-wort (Hypericum perforatum)

Dear Readers, last week I was exploring the car park at East Finchley tube station when I came across a plant that was entirely new to me – Perforate St John’s-wort. My copy of Harrap’s Wild Flowers describes it as ‘abundant, and by far the commonest St John’s-wort’. This may be so, but it’s fair to say that it’s a retiring and delicate plant, easily overshadowed by the more assertive ‘weeds’ that grow in the same habitat. It is easy to see that it’s a member of the same family as Rose of Sharon and Tutsan – it has five petals, a shaving-brush of stamen, and that butter-yellow colour that is so characteristic of the family. If you break a flower-bud, a reddish-purple liquid is produced.

IMG_4919But why on earth is it called ‘Perforate’? If we look closely at the leaves, we can see that they are covered in tiny translucent ‘windows’. These are resin glands, and are said to be responsible for the ‘foxy’ smell of the species, though I was not inclined to molest the small number of plants that I discovered to find out.

IMG_4935 (2)

By Matt Flavin

A great shot of the translucent spots from underneath – photo credit below.

Although this is a new plant to me, it is a native of Europe and Asia and has a long history of interaction with humans. Richard Mabey (in Flora Britannica) describes how, since prehistoric times, this plant was burned on the Midsummer Day Fires that were set all over the country. It was believed that these fires would purify communities and crops, and Perforate St. John’s-wort was one of the ‘sun-herbs’ which were thrown into the fire, probably because its yellow colour was thought to strengthen the power of the sun, while the smoke from the fires protected the fields against more malevolent summer manifestations, such as drought and wildfires.

Another story, attributed to the peoples of both the Isle of Man and the Isle of Wight is that if you accidentally stood on Perforate St-John’s-wort at night, you would promptly be carried off on a fairy horse from which you could not dismount until sunrise. By then, you could be anywhere, and would need to find your own way home. I find this such a delightful idea that I was almost tempted to creep back to the car park at dead of night with a thermos flask, some sandwiches and an Oyster card, just to see what would happen.

IMG_4927Later, as has so often been the case, the plant was absorbed by Christianity – the Feast of St John the Baptist is on June 24th, and so this pagan plant was renamed as a Christian one. The genus name Hypericum is supposedly derived from the Greek words Hyper (above) and eikon (holy picture), to describe the way that the plants were hung above icons on St. John’s day to protect the house against the evil eye. In a combination of the pagan and Christian uses of the plant, the flower-buds were gathered on 24th June, crushed and steeped in olive-oil, to produce a blood-red liquid that was called ‘Blood of Christ’ and was used for anointing.

IMG_4925The reason that most of us have heard of St John’s-wort, however, is because of its use as an anti-depressant. Reviews of the use of the plant have regularly indicated that it is more effective than a placebo for patients with major depression, as useful as standard anti-depressants in mild to moderate depression, and that it has fewer side-effects. It should be noted, however, that the studies performed in German-speaking countries (where herbal medicine is an accepted part of many treatment regimes)  returned much more positive results than those conducted in the US (where there is more reliance on synthetic medicines) (for more details see here). There is no doubt that this is a medicinally active and potent plant, and should therefore (as with all plant remedies) be treated with respect – it decreases the levels of oestrogen in the body by speeding up the rate with which the hormone is metabolised, and so may decrease the efficacy of the contraceptive pill. It may cause photosensitivity, and is also associated with aggravating psychosis and mania in patients with schizophrenia and bipolar disorder. I do note, however, that all these are also potential side-effects of many standard anti-depressants. I suspect that the main danger of this plant is using it alongside conventional anti-depressant drugs, and hence doubling up the dose of psychoactive chemicals. It also interacts with many other medications, including statins and HIV treatment protocols. Even so, it is given several pages on the website of Mind, the main UK mental health charity, and many people swear that using Perforate St John’s-wort has given them relief from the symptoms of anxiety and depression. So much power in a plant discovered at the back of a car park in North London!

By Prof. Dr. Thomé, Otto Wilhelm ( [Public domain], via Wikimedia Commons

Photo credit below.

As with so many plants that I have discovered through The Wednesday Weed, Perforate St John’s-wort has proved to be a problem in countries to which it is not native, especially Australia and the US. It is poisonous to grazing livestock if ingested in large quantities (indeed in Russia it is known as Zveroboi, or ‘beast-killer’), and some of the side-effects suffered by humans, such as photosensitivity and mania, are exhibited in animals unfortunate enough to have dined extensively on the plant. It is said that one of the effects of the plant is to make the suffering animal run in circles, resulting in strange ‘crop-circles’. The poisoned animal may be terrified of water, or may become so obsessed with it that it drowns. Fortunately, in places in which it is native it is unusual to see Perforate St.John’s-wort growing in anything like the quantities needed to cause these effects, but see the photo below of the plant growing in Australia for an idea of how densely-packed it can become.

By Peripitus (Own work) [GFDL ( or CC BY 3.0 (], via Wikimedia Commons

Perforate St. John’s-wort in Belair National Park, Australia. Photo credit below

What a remarkable plant this is. Its chemical composition means that it can both cure and poison, relieve distress and cause suffering. Of all the plants that I’ve featured on The Wednesday Weed, it is the one that has given me the most pause for thought. Modern Western society largely despises the healing power of plants, and is disrespectful of their undoubted power to heal or harm. In many places in the world, only a manufactured drug is considered efficacious, even though it may be originally derived from plants. Thank goodness for the people all over the world who are curious and knowledgeable about their botanical heritage, and who are working to preserve this priceless information for generations to come. Now, we just need to make sure that we also preserve the plants themselves.

Photo Credits

Perforated Leaves – By Matt Flavin

Illustration of Perforate St John’s-wort – By Prof. Dr. Thomé, Otto Wilhelm ( [Public domain], via Wikimedia Commons

Field of Perforate St.John’s-wort in Australia – By Peripitus (Own work) [GFDL ( or CC BY 3.0 (], via Wikimedia Commons

All other photos copyright Vivienne Palmer


Flora Britannica by Richard Mabey

The Plant Lives website curated by Sue Eland

4 thoughts on “Wednesday Weed – Perforate St John’s-wort

  1. Ann

    Fascinating, as usual. Here’s a little add-on, from an Italian book of Health Plants. ‘When he was physician to the Roman army, Dioscorides made great use of this herb … for lessening pain. … It is particularly effective after operations; for the after-effects of shock; and for spinal concussion and other injuries of the spine.’ Lots more uses, including for something called ‘brain-fag’ which sounds only too familiar.

    1. Bug Woman

      I frequently suffer from ‘brain-fag’ too, Ann. The Italian book sounds fascinating, and of course it lines up with what we now understand about the properties of the plant. It intrigues me how often modern science confirms what local herbalists and ‘ordinary’ people have known for hundreds of years…

  2. Monica

    I love your blog – someone just sent me the link. I’m one of the group who ‘look after’ the bank by East Finchley station that you’ve written about this time. Thank you for what you are doing!

    1. Bug Woman

      Hi Monica, so glad that you like the blog, and thank you for all the work that you’re doing at the station. And I’m sure the bees will be saying thank you, too….


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