Wednesday Weed – Caper Spurge

Dear Readers, I am always delighted when I find a ‘real’ weed that I haven’t written about before, and here is a doozy – Caper Spurge (Euphorbia Lathyrus) is a statuesque spurge, with leaves that start off long and narrow with a prominent white mid-rib, and end up more oval as they get near to the flower. It is the seed capsules that give the plant its name, however: they look deliciously toothsome, but sadly, like all parts of the plant, they are poisonous, oozing a blueish, latex-like sap if damaged.

Flower and seed capsule of caper spurge

Caper spurge is inherently a plant of the southern Mediterranean, Northern Africa and southwards right through to China, but it is thought to be an ancient introduction to the UK, and is often grown in gardens. Why, I wonder, was it introduced? Medicinally it has often been used as a purgative, but more intriguingly, it was also thought to deter moles. Vickery’s Folk Flora points out that this belief has given the plant the alternative names of mole-plant and in German it is known as maulwurfvertreiker or ‘mole deterrent’. However, the plant grows best in sandy soil where worms are scarce. As moles are fond of dining on earthworms it may be this, rather than the caper spurge, that explains the lack of ‘the little gentleman in black velvet’.

There is also a belief in Germany that the plant ‘keeps little mice away’.

In Somerset, the plant is said to be a deterrent to badgers because they dislike the sap – again, in Vickery’s Folk Flora, someone explains that you ‘have to keep breaking the stems’ to get the sap to flow.

Another explanation for the name ‘mole-plant’ is that the caustic sap might have been used to burn away ‘moles’ or beauty spots from the faces of those who considered them an impediment. Many euphorbias were used to treat warts in this way, so it doesn’t seem entirely unlikely.

And while we’re on the subject, here is a photo of a mole, probably the commonest British mammal that no one has ever seen (though we’ve all seen the results of their labours). Incidentally, other ways to keep moles out of the garden include ‘never speaking of them’ (much as you are not meant to mention ‘the Scottish Play’ to an actor), putting sardines in their runs (which would keep me out of the garden as well, though probably not the foxes and cats) and leaving hessian bags of human hair around the garden. Personally, I think I’d rather have the moles.

Photo One from

European mole (Talpa europea) (Photo One)

To return to the theme of caper spurge’s medicinal uses, Richard Mabey explains how the plant is found on the now uninhabited island of Steepholm in the Bristol Channel, along with the only colony of wild paeony (Paeonia mascula) in the UK and many other medicinal herbs such as henbane, coriander, wild leek, greater celandine and alexanders, all Mediterranean plants. Between 1166 and 1260 a community of Augustinian monks lived on the island, and it is likely that they planted a ‘physick garden’ in the equable oceanic climate. Certainly, Chaucer knew of caper spurge as ‘katapuce’ (mentioned in the Nun’s Priest’s Tale), and of its laxative properties, and Charlemagne insisted that it be grown in all herbal gardens in case anyone was ever in need of a good purge (the name ‘spurge’ comes from the Latin ‘expurgare’ which should give us a clue).

The sap was also used by beggars in medieval times who were in need of some additional sympathy – applied to the skin, it can cause extremely impressive blisters. One can only wonder at the depths of deprivation that made people to resort to such things. You most certainly do not want to get the sap in your eye, or onto any other ‘delicate parts’ – there are a lot of stories about chaps doing the weeding without gloves and then going to the toilet, followed by a rushed trip to Accident and Emergency when the effects of the sap became apparent.

Although caper spurge is toxic, goats will eat it, and the toxin can then be passed on via their milk. However the sap from caper spurge is also being considered as a possible biofuel, as it is extremely rich in hydrocarbons, and the plant will grow in relatively salty soils which are inhospitable to other plants so there would be little competition with food crops. The Nobel Prize winning scientist Melvin Calvin (1911-1997) (who discovered the Calvin Cycle of photosynthesis) estimated that cultivated caper spurge could produce 10-50 barrels of oil per acre per year, but whether there would be damage to the delicate coastal ecosystems involved remains to be seen.

Those fat little seed capsules, while not to be mistaken for capers, are entertaining in their own right: when ripe, they explode, catapulting the seeds for several metres. The seeds also float, and can be transported downriver if they happen to land in a suitable stream. Fortunately they are not particularly competitive, and are usually overwhelmed by more vigorous plants unless they happen to land in the perfect spot. They are now naturalised in many parts of the world, but do not appear to have become too overwhelming. In North America the plant is sometimes known as ‘gopher spurge’, so I wonder if this comes from a belief that, in addition to moles, mice and badgers, the plant discourages other mammals. And here is a photo of a gopher, just because I have never seen one. Those are extremely impressive incisors, I must say.

Photo Two by By LeonardoWeiss - Own work, CC BY 3.0,

Pocket Gopher (Thomomys bottae) (Photo Two)

And finally, here is a titbit that I found while looking around for a poem on caper spurge. The artist John Northcote Nash (1893 -1977), was the younger brother of the WWI artist Paul Nash, but his creative endeavours took him in the direction of botanical woodcuts. In his wonderful book ‘Wildwood: A Journey Through Trees‘, the late Roger Deakin (gone much, much too soon), wrote about Nash’s masterpiece, ‘Poisonous Plants: Deadly, Dangerous and Suspect‘ (1922)

In a review of an edition of Nash woodcuts published in Hortus in 1988, Ronald Blythe writes:

‘His garden was always plentifully supplied with henbane, hemlock, monk’s hood, foxglove, meadow saffron, spurge laurel, datura, caper spurge, herb Paris, Helleborus foetidus and other such species which he had often been found staring at, much as one might at a murderer. He was proud, not only of their robust growth, but of their capabilities, and I have often watched him cast a wary eye over the gaunt reaches of the henbane. Gardens were not entirely benign places to him: they contained their darker moments.”

I think that any garden, closely observed, is awash with birth, life, death and decay, and that is, of course, exactly how it has to be. So many gardeners (myself included) have spells of railing against the unfairness of it all, when a heron eats a frog or a much-loved plant succumbs, or the slugs seem overwhelming. The foxglove feeds the bumblebee, and the caper spurge sits there innocently until you break a stem and rub your eye. Nature is not hell, but nor is it Disneyland.

Photo Credits

Photo One from

Photo Two by By LeonardoWeiss – Own work, CC BY 3.0,




20 thoughts on “Wednesday Weed – Caper Spurge

  1. Anne

    A fascinating read – lovely to meet a plant I have not heard of before. How I laughed at the keeping moles at bay remedies: there are a variety of different ones here too but, like you, I’d rather keep the moles and simply rake over their mole heaps (ours are really mole rats). Your final paragraph resonates with me in terms of my attitude to gardening.

  2. tonytomeo

    How odd that so many of your weeds are the same weeds that we have here. This one only appeared here in the past ten years or so, along with another similar species.

    1. Bug Woman

      How strange that it’s only arrived now! Some euphorbias are very decorative, but not this one. A lot of alien plants in the UK have come over in the soil with more desirable garden centre plants, so maybe that’s a route in. At least caper spurge doesn’t seem particularly invasive….

      1. tonytomeo

        Yes, it is not as invasive as others. Gopher purge was supposedly planted around gardens before it naturalized. I am told that it works, but only if grown in a continuous row around the garden. Gophers do not go through it even on the surface. I think they might if they were hungry enough.

  3. Sarah Ann Bronkhorst

    Got several in our garden and feel rather ambivalent about them. They have an oddly triffid-like look but bees seek out those tiny yellow flowers so I must learn to admire, if not love them.

    1. Bug Woman

      Your garden is such a useful source of plants to write about, Ann – I shall have to pop down with my camera when I’m back from Austria. I still haven’t worked out what that clover/gorse-like one on the corner is….

  4. Sarah Ann Bronkhorst

    Correctly named. Much loved by bees but it is, however, a THUG. I intend to hack it back once the bees have done with it.

  5. colin kirkham

    I have had this plant in my garden for thirty years and have finally identified it – many thanks. I give spare plants away free of charge at my gate and have never until now, been able to tell the recipients any information about this particular plant. I shall hence forth wax lyrical!!

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  8. gurig

    Just found a related species called Euphorbia Helioscopia, or Madwomanโ€™s Milk, and now since I have children I want to get this outta my garden! Problem is, how to do it without chemicals?

    1. Bug Woman Post author

      Hi there, are your children actually likely to interact with this plant? Are they of an age to understand that they shouldn’t eat things that they can’t identify? There are many, many garden plants that are poisonous, but very few children are affected by them because they know to leave them alone. Failing that, I suspect you’re going to be putting on gloves and pulling them up individually very carefully ๐Ÿ™

  9. Andy

    A fabulous thank you for your lovely blog post,I found a caper spurge in my garden recently and wondered what it was it is a beautiful and weird looking plant but so beautiful looking,I took a picture on my mobile and Google match it and and connected me to you, thanks for your info,yours truly,Andy


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