In praise of the Polygonaceae

What does the name Polygonum mean to you? Maybe nothing, or maybe you think of nuisance plants such as dock, knotgrass and knotweed.  The genus Polygonum gives its name to the plant family Polygonaceae; some 1200 species in around 48 genera, many with the characteristic multiple swollen stem nodes hinted at by the family name (goni means knee or joint, in Greek).  The ‘knobbly knees’ come from pair of fused stipules at the base of each leaf called an ochrea.

Persicaria capitata, Uttarakhand, showing ochrea

The Polygonaceae have tepals, rather than separate petals and sepals, though these can be brightly coloured, as above.  The fruits are hard, three-angled nuts, each containing just a single seed. Buckwheat (on which more, below) apparently gets its English name from the fact that the fruits look like tiny Beech nuts. The family has a pretty global distribution, though favouring northern hemisphere temperate regions.  The most familiar genera in the UK are probably Polygonum, Persicaria, Rheum, Rumex and Fallopia.

Rumex species (docks and sorrel) are probably no-one’s favourite plants, spreading rapidly as they do over waste land and giving it rather an unloved appearance in the autumn, with their tall, rusty brown seed heads.  I for one, though, am prepared to put up with the seedlings which spring up all over my allotment, in return for a summer-long supply of lovely, lemony sorrel leaves for my salads. Sorrel also makes a delicious sauce for fish, though the same oxalic acid which gives the sharp flavour is a major component of the calcium oxalate in kidney stones, so some restraint is needed!

Rheum (rhubarb) is another edible member of the family – not the leaves this time, but their stalks or petioles.  Allotment favourites are jelly, made with the earliest pink forced rhubarb, lightly flavoured with cardamom, and rhubarb and ginger fool – real seasonal spring treats which I’m looking forward to once the snow goes.

I’ve written before about the amazing Himalayan rhubarb but, in fact, all rhubarb originally came from Asia and was originally brought into Europe along the Silk Road some in the 15th Century. Our modern cultivated Rheum rhabarbarum is thought to be a descendant of a variety grown along the Volga river (originally the Rhā), for centuries.

The third edible genus, less familiar now in the UK, is Fagopyrum or buckwheat, which we came across growing in the beautiful Baspa valley in the Kinnaur region of Himachal Pradesh.  Our guidebook simply called it by its local name, ogla, and implied the plant was specific to the region.

Closer inspection, however, showed the crop to be buckwheat, Fagopyrum esculentum – a so-called pseudocereal. Although not a member of the grass family, buckwheat’s carbohydrate-rich grains can be ground up to make a nutritious flour.  Less devout Hindus cook with buckwheat on fast days, apparently, to fulfil their obligation not to eat cereals.  The crop’s short growing season (10 -12 weeks) is a considerable advantage at altitudes of around 2700 m, as is the fact that it thrives on less fertile, acidic soil.  Sadly, we were not lucky enough to taste the buckwheat pancakes or pakoras which are a speciality here – the young lads running the tented camp where we stayed at Sangla had limited culinary expertise, to put it politely.  Buckwheat used to be grown widely in Britain and ground to produce poor man’s flour, as well as food for cattle and hens and I still buy it to make galettes, the delicious, nutty-flavoured savoury pancakes we first ate in Normandy.

Polygonum, the genus which gives the family its name, now has rather a limited number of knotgrass species growing wild in the UK; many species previously classified as Polygonum (such as the Bistorts and Water-peppers) have been reassigned to the genus Persicaria.  We found common knotgrass (Polygonum aviculare) growing near Thajiwas, in Kashmir, but it is equally at home in Britain.

Common knotgrass, Polygonum aviculare (Thajiwas)

The genus Polygonum still has plenty of species in the Indian Himalayas though. We found Pamir knotweed (Polgonum sibiricum) growing with varying levels of red pigment in its leaves in the salty ground around Tso Moriri lake, at around 4500 m above sea level.

Pamir knotweed (Polgonum sibiricum) on the shoreline of Tso Moriri

Fuzzy knotweed, Polygonum paronychioides, was more of a surprise.  We found this on the arid slopes below Shergol monastery in Ladakh and it took me a long time to work out that this was, in fact, a Polygonum.   I’d assumed it to be one of the drought-tolerant Crassulaceae. By now, something of a theme should be emerging about the habitats in which these tough plants can thrive!

Shergol monastery, Ladakh and Polygonum paronychioides

Another important group of Polygonums are the fleece flowers – perhaps no-one has got around to reassigning these yet, as they look pretty bistort-like to me! Polygonum affine clads dry mountain slopes, giving a pink glow rather like heather growing on a Scottish moor.  In the Valley of Flowers we saw P. vaccinifolium nestling in more sheltered spots.

Polygonum affine, by the Manali-Leh road

Polygonum vaccinifolium, Valley of Flowers

Our British bistorts, now in the genus Persicaria, are often used as garden ornamentals but their natural habitat is much like that of the fleece flowers of the Himalayas.  They have a multitude of common names, according to Geoffrey Grigson, perhaps the oddest of which is Easter Ledge.  Easter Ledger pudding is apparently traditional Cumbrian fare in the week leading up to Easter and is supposed to help with conception.  Grigson’s recipe doesn’t sound that appealing to me, I have to say – banish any idea of tasty desserts! ‘Pick young Easter Ledge leaves, and drop them with leaves of Dandelions, Lady’s Mantle or Nettle into boiling water and cook for 20 minute.  Strain and chop.  Add a little boiled barley, a chopped hard-boiled egg, butter, pepper, salt.  Heat in a saucepan and press into a pudding basin. Serve with veal and bacon.’

Persicaria bistorta (previously Polygonum bistorta), Weardale, Durham

In a nice link with an earlier blog on orchids, Bistort also features in the final scene of the 16thCentury ‘Hunt of the Unicorn’ tapestries, where the injured unicorn is tethered to a pomegranate tree. An Early purple orchid and a Lords-and-Ladies plant, both seen as plants of desire, are silhouetted against the unicorn’s white flank whilst next to its right forelegs is Bistort, seen as a plant of virtue.

unicorn_tapestry.jpg

Not all Persicarias are quite so virtuous though – more in my next blog….

Grigson, G. (1958) The Englishman’s Flora

2 thoughts on “In praise of the Polygonaceae

  1. Pingback: Pesky Persicarias | heatherkellyblog

  2. Pingback: Crowtrees LNR, June 2018 | heatherkellyblog

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