Wednesday Weed – Knotgrass

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…..

Knotgrass (Polygonum aviculare sp)

Dear Readers, you will know by now that I love investigating the most common and overlooked of ‘weeds’, and this week’s subject is what my American friends would call ‘a doozy’. Knotgrass is popping up all over East Finchley at the moment, straggling from between paving stones and emerging from cracked concrete. It has a sprawling, nonchalant habit, tiny flowers and a jointed stem that reminds me a little of bamboo. But as usual, there is more to knotgrass than meets the eye.

Knotgrass is a member of the Polygonaceae, a family that includes redshank, Japanese knotweed and Russian vine . The name ‘Polygonaceae’ derives from the Greek phrase meaning ‘many knees’ – if you look at the stem of knotgrass you can see lots of little ‘joints’ or nodes. I learned with some delight that the Middle English name for this plant is ‘ars-smerte’ – it was once used in a lotion for haemorrhoids, and as many of the plants in this family are hot and peppery, I think we can imagine the reason.

Although knotgrass is a relatively uninteresting plant to the casual observer, I would draw the attention of anyone with a magnifying glass to the flowers and buds, which are rather delightful.

By Dalgial (Own work) [CC BY-SA 3.0 (], via Wikimedia Commons

Knotgrass flowers (Photo One – see credit below)

As you will know, I am often flabbergasted when I am researching my ‘weeds’ and today is no exception. In his novel ‘The Man Who Laughs’, Victor Hugo tells of how ‘artificial dwarves’ were created by Spanish child-buyers or Comprachicos. Hugo compares their work of deliberate mutilation to those who create bonsai trees. The Comprachicos stunted the growth of the children   “by anointing babies’ spines with the grease of bats, moles and dormice” and using drugs such as “dwarf elder, knotgrass, and daisy juice”, in order to create tiny people who could be sold as entertainment at court, or as beggars. Although there is some question about how accurate Hugo’s depiction of these practices was, Shakespeare certainly knew that knotgrass had a reputation in this regard. Here is a description of the diminutive Hermia from A Midsummer Night’s Dream:

Get you gone, dwarf;
You minimus, of hindering knot-grass made;

And here, in a play by Beaumont and Fletcher, the Coxcomb says that they

Want a boy

Kept under for a year on milk and knotgrass‘.

The illustration below is of the Hermia scene described above in  A Midsummer Night’s Dream, painted by none other than William Heath Robinson (1872-1944), the man who created the extraordinary pictures of machines that have led to any ingenious, Wallace and Gromit-esque contraption being described as being ‘Heath Robinson’.

A Midsummer Night’s Dream (illustration by William Heath Robinson) (Public Domain)

And here, for your delectation, is the William Heath Robinson Naval Cloud Dispeller.

William Heath Robinson (Naval Cloud Dispeller) (Public Domain)

But I digress, as usual.

You might think that knotgrass looks most unappetising, but it has been used as food all over the world (the plant seems to be pretty much universal).In Vietnam, the plant is known as rau đắng, and is used in a hot and sour stew called Canh chua, which looks most delicious.

By Jason Hutchens - Flickr: Canh Chua, CC BY 2.0,

Canh chua (Photo Two – see credit below)

Several foragers mention that the young leaves can be used in salads, and that the seeds can be milled into flour (knotgrass is closely related to buckwheat). You would need a lot of patience and a clean supply of the plant for either of those activities, however: because of its low-growing habit and preference for paving stones, knotgrass is frequently trampled underfoot and peed upon by dogs, neither of which makes it particularly appetising.

I do wonder if the species name of the plant, aviculare, refers to small birds being partial to the seeds, though. They look just about the right size for goldfinches.

By Stefan.lefnaer - Own work, CC BY-SA 4.0,

A knotgrass seed. You’d need a few for a loaf, that’s for sure….(Photo Three – credit below)

I did learn that the plant has a single taproot which can penetrate to nearly four feet, which makes it very drought-resistant, another desirable attribute in an exposed city plant. It is also said to be rich in zinc.

In Turkey, the plant is known as Madimak, and here is a recipe from the Turkish Yummies website

Generally, knotgrass has been seen as a famine food, something to get people through when nothing else was available. It is, however, seen as food by many insects, including the bloodwing moth, whose caterpillar tries to camouflage itself as a thorny twig.

By Bj.schoenmakers - Own work, CC0,

Bloodwing (Timandra comae) caterpillar (Photo Four – see credit below)

By Marcello Consolo at

Adult Bloodwing (Timandra comae ) (Photo Six – credit below)

As well as being used for piles, knotgrass has been used as a diuretic, and for the treatment of urinary tract infections. It is an antihelminthic (I love this word – it means that it can be used to expel parasitic worms), and has been used to break down mucus when people have lung and throat infections.

You might think that such a small and humble plant would not have made much of an impact on poets (except for its child-shrinking abilities, of course). But here is Keats, in ‘The Eve of St Agnes’:’

A casement high and triple-arch’d there was,
       All garlanded with carven imag’ries
       Of fruits, and flowers, and bunches of knot-grass,
       And diamonded with panes of quaint device,
       Innumerable of stains and splendid dyes,
       As are the tiger-moth’s deep-damask’d wings;
       And in the midst, ‘mong thousand heraldries,
       And twilight saints, and dim emblazonings,
A shielded scutcheon blush’d with blood of queens and kings.


And here is Oliver Wendell Holmes from his poem ‘The Exile’s Secret’

Who sees unmoved, a ruin at his feet,
The lowliest home where human hearts have beat?
Its hearthstone, shaded with the bistre stain
A century’s showery torrents wash in vain;
Its starving orchard, where the thistle blows
And mossy trunks still mark the broken rows;
Its chimney-loving poplar, oftenest seen
Next an old roof, or where a roof has been;
Its knot-grass, plantain,–all the social weeds,
Man’s mute companions, following where he leads;
Its dwarfed, pale flowers, that show their straggling heads,
Sown by the wind from grass-choked garden-beds;
Its woodbine, creeping where it used to climb;
Its roses, breathing of the olden time;
All the poor shows the curious idler sees,
As life’s thin shadows waste by slow degrees,
Till naught remains, the saddening tale to tell,
Save home’s last wrecks,–the cellar and the well?

‘Man’s mute companions’, indeed. But I sometimes wonder if they would still speak to us, as they used to, if we paid them more attention.

By Dalgial - Own work, CC BY-SA 3.0,

Photo Six (Credit below)


Photo Credits

Photo One (knotgrass flowers) – By Dalgial (Own work) [CC BY-SA 3.0 (], via Wikimedia Commons

Photo Two (Vietnamese hotpot) – By Jason Hutchens – Flickr: Canh Chua, CC BY 2.0,

Photo Three (knotgrass seed) – By Stefan.lefnaer – Own work, CC BY-SA 4.0,

Photo Four (Bloodwing caterpillar) – By Bj.schoenmakers – Own work, CC0,

Photo Five (Adult bloodwing) – By Marcello Consolo at

Photo Six (Knotgrass) – By Dalgial – Own work, CC BY-SA 3.0,




6 thoughts on “Wednesday Weed – Knotgrass

  1. Fran and Bobby Freelove

    This is one little wildflower that we couldn’t put a name to, there is so much of it on our daily walk through the woods and meadows. Like you we study all the wildflowers, butterflies and insects so it’s nice to be able to name something. When we saw it on your blog we said that’s the plant that we wanted to name, we checked to make sure today ( all the time being danced round by a large dragonfly) and yes, you’ve solved it for us, thank you Bugwoman.

    1. Bug Woman

      So glad to have been able to help, Fran and Bobby. I love it when I’m able to identify a plant that’s been confusing me. And i love dragonflies too – they often seem so curious, as if they’re trying to work out what on earth humans are.

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