STINGING NETTLE (Urtica dioica)

 

STINGING NETTLE (Urtica dioica) Family: Urticaceae

The stinging nettle is without doubt the prince of all the many edible wild leafy greens that are available throughout the British Isles. It is a perennial plant that grows in damp woodland and hedgerows (for distribution maps see Online Atlas of the British and Irish Flora; see also: Taylor 2009). The habitat in which nettles are most consistently abundant is riverine willow-alder woodland (e.g., willow-alder carr[i]) where it is co-dominant throughout glades and in partial shade with Meadow Sweet (Filipendula ulmaria) and two species of Hemp Nettle (Galeopsis spp.).

Nettles grow on rich, fertile soils with a high nitrogen content (e.g., on land that is enriched by the addition of midden deposits or animal manure; Taylor 2009: 1439). They also thrive where there are accumulations of potash (potassium carbonate: K₂CO₃) and phosphates (PO₄^3-) that are derived from faeces and bones, such as in areas once occupied by humans or where livestock was stalled (Taylor 2009: 1440; see also CABI Invasive Species Compendium). The presence of nettles in archaeobotanical samples recovered from prehistoric and historic sites is therefore often used as evidence of habitation and as an indication of where human and animal waste had been disposed of around dwelling places (Behre and Jacomet 1991: 103; Stace 1995: 144).

 

When and where to gather nettles

Contrary to what is often suggested in the literature nettles can be used year round providing parts of the plants that are well into flowering or that have started to seed are avoided. But where to collect the nettles should be given careful consideration; for example, even in mid-winter it’s usually possible to find the odd sheltered nook under a hedgerow where the plants are better protected from frost and at least a few handfuls of small shoots can be gathered. Apart from when gathering these mid-winter shoots, always try to harvest nettle leaves from plants growing in partial shade and where the soil is fairly moist. In such habitats they flower much later, the leaves are larger, more tender and succulent, paler green and milder flavoured. These larger leaves are also more efficient to gather. When nettles grow in full sunshine, especially on dry ground, they flower and seed much earlier and produce much coarser, smaller leaves with reddish-purple veins that are fibrous to eat and can taste bitter.

 

Nettle management

However, even the coarsest, straggly remnants of plants that have gone to seed can still be used. All that’s required is to cut back the old shoots close to the ground with a sickle or swap[ii] and allow new young ones to grow from the base. In open habitats, these new shoots come back fresh, tender and green. Cutting back stands of nettles thus prolongs the period during which they’re edible over much of the year until they’re affected by hard frosts. Although by late October these fresh shoots are rather chewy when eaten as spinach.

 

Harvesting nettles

Even with the most succulent of stands of nettles it’s always advisable to target the youngest leaves. Harvesting is best done by first pinching out the top truss of four to six very small leaves at the very tip of the shoot and then, working back down the plant, by picking off the individual leaf blades leaving behind the leaf stalks. These leaf-stalks tend to be tough and chewy and more or less inedible (for descriptions of the use of nettle fibres see later section on Other Uses; see also: Bergfjord et al. 2012; Harwood and Edom 2013; Lukešová et al. 2017; Suomela et al. 2018). The leaves grow in pairs and, depending on how the nettles are going to be used and what quantities are needed, it’s best to start by taking just two or three pairs, but if the plants are really tender and light green with very succulent leaves, it’s possible to work down from the shoot tip collecting three, four, or even five pairs of leaf blades.

 

Nettle stings

Children—with their very tender skin—are particularly prone to getting hurt by nettle stings[iii]. When brushed against, the microscopic glassy tips of the numerous stinging hairs of the nettle plant break off and penetrate the skin and in so doing release a range of chemicals, including formic acid, histamine, acetylcholine, and serotonin[iv], thus causing skin irritation and a burning sensation[v]. Toddlers are especially vulnerable because the stinging leaves are at face height. All children know to rub the inflamed sores caused by the nettle stings with tender young dock leaves (Rumex spp.). However, if young plantain leaves (Plantago spp.) are applied in the same way they are generally more effective (for information on how nettle stings are treated around the world see Plant Lore).

 

Nettle leaves as food

Nettle leaves are an important source of protein (see PlantsFor A Future [PFAF] database). Stinging nettle shoots comprise ~90% moisture, up to 3.7% proteins, 0.6% fat, 2.1% ash, 6.4% dietary fibre and 7.1% total carbohydrate, and they have a calorific value of 45.7 kcal/100g (Adhikari et al. 2016; Kregiel et al. 2018; Rutto et al. 2013; Taylor 2009: 1442). Nettles are valuable nutritional components to any diet because they are also rich sources of vitamins A and C, calcium, iron and sodium (Rutto et al. 2013: figure 2). In addition, they contain glucocinins, which cause blood sugar levels to drop, and so if after eating nettles you briefly feel less energetic that’s the reason why (Seiman et al. 2018).

Singed nettle leaves make a tasty, surprisingly filling and easy-to-prepare snack. After gathering nettle shoots with a good length of stalk, grasp the stem bases and pass the leaves through the flames of the fire (or hold them close to hot embers) until the leaves are wilted. This shrivels microscopic hairs that cover all parts of the plant thereby neutralising the sting. Always eat the shoots freshly singed otherwise if they dry out and become ‘nettle crisps’ they are very bristly and make extremely coarse eating.

There are many other ways of cooking nettles and with the arrival of spring nettle soup is particularly welcome. A selection of wild ingredients (e.g., wild garlic (Allium ursinum), bramble tips (Rubus fruticosus agg.) and young hawthorn (Crataegus monogyna) leaves) can be added to enhance the flavour of the soup, as well as some kitchen staples, such as potatoes, onions and celery. Begin by frying the onions in oil until soft and then add water or stock and simmer for about 10 minutes. Add the potatoes, celery and other supplementary ingredients and cook until soft. Finally mix in the nettle leaves and any additional wild leafy greens. Once the leaves are wilted blend the mixture into a purée, add seasoning and then enjoy this tasty soup.

Mrs Grieve (1931/1992: 577) gives recipes for nettle pudding (the ingredients of which include: one gallon of young nettle tops, two good sized leeks or onions, two heads of broccoli or small cabbage, or Brussels sprouts, and ¼ lb of rice) and nettle beer (made from young nettle tops, three-four handfuls of dandelions (Taraxacum sp.) and clivers/cleavers (Galium sp.) and 2 oz of bruised ginger), which was apparently good for easing gouty and rheumatic pains. Nettle leaves are tasty if boiled like spinach, are also excellent when added to omelettes, and a thick nettle purée is a perfect addition to toasted cheese. In addition, they can be used as a form of vegetable ‘rennet’ to coagulate milk and make milk curds or cheese (Fiol et al. 2016). Coagulation of casein (the milk protein) takes place when the pH of the milk is lowered (e.g., the milk is acidified) and in normal cheese-making rennet (enzymes derived from the stomachs of ruminant mammals) is used for this purpose but the naturally occurring acids in the nettles are also found to fulfil this same role[vi] (for examples of other ways to prepare and eat nettles see: Robin Harford’s Foraging Guide to Wild Edible Plants of Britain. 

 

Therapeutic uses of Nettles

The therapeutic benefits of nettles have long been recognised and they have been, and still are, used to treat a diverse range of ailments (Kregiel et al. 2018; Pant and Sundriyal 2016; see also: American Botanical Council herbal).  ‘Urtication’ – or deliberately stinging parts of the body to relieve (or counteract) debilitating symptoms, is one of the oldest known remedies used to alleviate musculoskeletal pain (e.g., affecting muscles, bones, tendons and ligaments; Alford 2008; Randall et al. 2000). Alford (2008: 964) notes that there is evidence for their use in this way by Roman soldiers in Britain who were apparently well aware of the restorative effect brought about by the warming sensation of the nettle sting. In her Lancet article ‘Nettles take the sting out of arthritis pain’ Marilynn Larkin (2000) endorses the effectiveness of intentionally using Urtica dioica leaves to sting patients with osteoarthritis pain in their hands. Similarly, the extracts of roots, stems and leaves[vii] are proven to reduce inflammation in rheumatoid- and osteo-arthritis, although as Johnson et al. (2013) stress, more exploratory clinical trials are required to fully understand the processes by which the active components in the nettles bring about joint pain relief. It has also been shown that extracts of nettle plants used in topical applications have antioxidant properties that are known to reduce the effects of ageing (Bourgeois et al. 2016; for other nettle remedies see Grieve 1931/1992: 577-578).

 

Ethnographic accounts of the medicinal uses of Nettles

Traditional uses of nettles as reported in the ethnographic literature are many and varied. In the Riverside region of Navarra, in northern Iberia, Urtica dioica is used to treat several cardiovascular-related problems; for example, an infusion (taken orally) of the leaves is used to improve blood circulation, lower blood pressure and, more generally, to cleanse or purify the blood (Calvo et al. 2011). Based on the same survey results of c.150 elderly residents in the region, it was noted that a decoction of nettles is given to reduce blood sugar levels. In the villages of Kırklareli Province in Turkish Thrace (the European part of Turkey) and Mihalgazi district (in Eskişehir, northwest Turkey) the leaves—taken orally in decoctions or infusions—are also remedies for hypertension (Kültür 2007; Uzun and Kaya 2016). In both these regions a multitude of additional uses for parts of the nettle plants (made into decoctions, infusions and/or poultices) are cited; included in the long lists are those for curing stomach ache, constipation, haemorrhoids, high cholesterol, diabetes, nephritis, prostatitis and baldness (Kültür 2007: table 1; Uzun and Kaya 2016: table 1). Respiratory problems (e.g., bronchitis) are commonly treated by drinking a decoction of the leaves in the Elazığ Province of eastern Turkey (Hayta et al. 2014). Extracts of nettle leaves, seeds and roots are also frequently used in Turkey as antimicrobial medications to treat infection caused by Gram-positive and Gram-negative bacteria (Kregiel et al. 2018: table 4). The diversity of nettle use is further exemplified in the Ancona district of the Marche region of Central Italy where boiled leaves prepared as a poultice are shown to be effective for healing wounds and crushed leaves placed in the nose can staunch bleeding (Lucchetti et al. 2019; for more descriptions of traditional uses of nettles see: Lumpert and Kreft 2017 (Slovenia); Sõukand et al. 2017 (Belarus); Tagarelli 2010 (S Italy)).

 

Ethnobotanical accounts of preparing and consuming Nettles

Kregiel et al. (2018) summarise a wide range of edible uses for Urtica species and, in addition to those already mentioned in the earlier section, they state that a dish made with boiled nettles and walnuts is frequently prepared in Georgia (known as pkhali, ფხალი) and that a soup made of fermented wheat bran, vegetables and young nettle leaves is eaten in Romania (nettle sour soup, Ciorbă de urzici; see also: Costa et al. 2013). In their review of edible wild plants used in Poland at the end of the 18^th century Łuczaj and Szymański (2007) note that stinging nettles are included in the list of species used as famine foods at times when other food resources were in short supply. Nettle tops (harvested in spring) were often boiled and/or fried and eaten with potatoes, kasza (cracked buckwheat or cracked cereals), eggs or fat. The leaves are used to flavour risottos and as a filling for ravioli in Central Italy (Lucchetti et al. 2019). And in the Liubań district of Belarus they are added to bread to give flavour and provide mineral and nutrient supplements (Sõukand et al. 2017; for more traditional recipes that include nettles see: Guarrera and Savo 2016 (Italy); Lumpert and Kreft 2017 (Slovenia)).

 

Other uses

There is evidence for the use of Urtica dioica fibres as far back as the Bronze Age (Harwood and Edom 2012; see also following section on Prehistoric and Historic Uses). Nettles have continued to be exploited to make cloth and cord up to the present day and there has been a recent revival of interest in their use in the fashion industry as a sustainable alternative to other more environmentally detrimental products (e.g., man-made fibres such as nylon, acrylic and polyester; Fashion Industry News). Collection of nettles for fibre on an industrial scale in Germany during WWI when other textiles were scarce is a frequently cited example of their use (Harwood and Edom 2012: 109-110; see also Grieve 1931/1992: 575-576), and during which time German soldiers apparently had uniforms and other paraphernalia made of nettle fibres (Western Front Witness). Harwood and Edom (2012) give details of the amounts that were necessary to harvest:

“As a result, 10,000 tonnes of wild nettles were collected, mainly by children in collaboration with the military authorities. This harvest reportedly yielded c. 1,500 tons of fibre. The whole operation was controlled by Nesselanbau Gesellschaft (Nettle Cultivation Company), an organisation established in Berlin. ….. A yarn known as Nesselgarn was spun from which the cloth Nesseltuch was woven. After bleaching to a pure white, this cloth apparently resembled linen.”

and they further elaborate other ways in which the nettles were used:

“In addition to its use for textiles the nettle plant proved to have a multitude of uses — 3,000 tons of food products were extracted from the leaves and 3,000 tons of material were utilised by the paper and chemical industries.”

As part of the war effort in the UK during WWII to make up for the extreme shortages in   supplies of drugs people were encouraged to collect wild plants (under the guidance of the Vegetable Drugs Committee founded in 1941[viii]) that had known economic as well as therapeutic importance and these included nettles, which were used for the production of dye from chlorophyll (Harwood and Edom 2013: 111-112). The colour of the dye was suitable for camouflage purposes on military uniforms and as Harwood and Edom (2012) note:

“…anecdotes suggest the permanent green dye was used to colour camouflage nets that were used ahead of the D-Day landings…”

In the Ancona district of the Marche region of Central Italy the dye derived from nettle leaves is used to colour fishnets green (Lucchetti et al. 2019). Other uses of the leaves in this region are as a repellant (in the form of a decoction) against parasites in orchards, as a feed for hens, turkeys and geese to increase egg laying, and as a digestive aid for cattle (Lucchetti et al. 2019: table 1). The beneficial value of nettle leaves for livestock is also recognised in the Liubań district of Belarus, where they are used as a fodder for cattle and are given as a decoction to piglets to make them stronger (Sõukand et al. 2017: table 1).

 

Prehistoric and historic uses

We have documentary evidence for the use of nettles in the Roman period thanks to Pliny the Elder (23-79 AD)[ix] in his magnum opus Natural History, in which he wrote extensively about the curative properties of the plants:

“What can be more hateful than the nettle? Yet this plant, to say nothing of the oil which I have said is made from it in Egypt, simply abounds in remedies. Nicander assures us that its seed counteracts hemlock, and also the poison of fungi and of mercury. Apollodorus says that with the broth of boiled tortoise it is good for salamander bites, and as an antidote for henbane, snake bites and scorpion stings.” (excerpt from book 22, translated by Rackham et al. 1938)

Nettles are also listed amongst the plants with curative properties in the Nine Herbs Charm in the Anglo Saxon Lacnunga—a 10^th/11^th century AD text that documents a miscellany of cures and charms (Bolotina 2015). In the charm (or prayer) the nettle is described as having a range of special qualities, as shown in this excerpt from the Lacnunga LXXIX-LXXXII (cited in Wyrtig), which gives the original Old English together with its translation:

stiðe heo hatte                                                 nettle she is called

wiðstunað heo attre                                        stands she against poison

wreceð heo wraðan                                         she drives out wretchedness

weorpeð ut attor.                                            throws out poison.

 + þis is seo wyrt                                             + this is the plant that

seo wiþ wyrm gefeaht                                     against the worm battled

þeos mæg wið attre                                         this mighty against poison

heo mæg wið onflyge                                      she mighty against infection

heo mæg wið  þam laþan                                she mighty against evil that

ðe geond lond fereþ .                                      goes through the land.

The soft, fleshy vegetative parts of plants rarely survive in archaeological deposits (e.g., either in waterlogged or charred form) and so the likelihood of finding nettle leaves at sites of any period is unlikely (Colledge and Conolly 2014). The presence of Urtica dioica seeds (which are commonly preserved) is not necessarily an indication that the leaves were consumed, given that they are best eaten when the plant is young—prior to seeds being produced—rather than when it’s mature and seeds are present. Their occurrence at settlements is, however, suggestive that nettles were growing in the vicinity, which as stated above, is unsurprising as they favour nitrogen-rich soils, such as middens, animal pens, etc. typically found close to habitation sites.

The most tangible evidence for the past use of nettles is the fibres that are preserved on archaeological sites. An amazing array of organic materials was found in an Early Bronze Age cremation cist (dated between 1900 and 1600 cal BC) at Whitehorse Hill on Dartmoor where artefacts preserved in the burial of a young adult included what was described as a: “band of woven textile with decorative leather borders” (Harris and Jones 2017: 22). Aerobic decay of these materials had been prevented due to the fact that the cist was located within a peat-rich mound. High magnification using scanning electron microscopy confirmed that fibres of the textile of the band were of nettle (Urtica dioica; Harris and Jones 2017: figure 3). In a similar context, a fragment of textile (dated to 940-750 BC) identified as being made from woven nettle fibres was found wrapped round cremated remains in a Late Bronze Age burial urn placed within the Lusehøj burial mound at Voldtofte in Denmark (Bergfjord et al. 2012; see also ScienceNorway). 

 

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[i] See entry for willow-alder carr in: An Introduction to British Woodlands and their Management: http://www.countrysideinfo.co.uk/woodland_manage/broadlf3.htm [accessed 02.07.19]

[ii] For description of a ‘swap’ see: https://pecmastergardeners.files.wordpress.com/2017/05/swap-hook.pdf [accessed: 24.06.19]

[iii] For a personal account of childhood memories of being stung by nettles see: https://www.theguardian.com/environment/2019/sep/30/country-diary-armies-of-nettles-are-ready-to-strike [accessed: 30.09.19]

[iv] For details of the chemistry of nettle stings see: https://www.compoundchem.com/2015/06/04/nettles/ [accessed: 25.06.19]

[v] The name Urtica is from the Latin ‘urere’ meaning to burn or scorch: http://latindictionary.wikidot.com/verb:urere [accessed: 08.07.19]. And appropriately, the German name for stinging nettle is Brennessel, which translates as: the ‘burn-nettle’.

[vi] Cornish Yarg is a cheese that is wrapped in nettles to make an edible rind. The increase in acidity in the outer surface of the cheese caused by the nettle leaves stimulates the break down of the curds and formation of a hardened crust: https://en.wikipedia.org/wiki/Cornish_Yarg. [accessed: 14.10.19]

[vii] In a pilot study the authors note that the nettle extract was applied topically. Other authors demonstrate the efficacy of taking an oral infusion of nettles (e.g., the leaves) to treat arthritic pain (Ghasemian et al. 2016).

[viii] “The Vegetable Drugs Committee, established in 1941, was advised by the Medical Research Council’s Therapeutic Requirements Committee. More than 70 County Medicinal Herb Committees, which drew primarily on the Women’s Institute and the Scottish Women’s Rural Institutes, were set up under its leadership. This framework not only meant that small collections of particular plant materials could be amassed in central locations to allow wholesale levels of production, but also that the women (and men) involved in collection could receive lectures and training from the pharmaceutical industry and schools of pharmacy to improve their knowledge of what they were collecting and why.” Excerpt from The Pharmaceutical Journal 2017 (Medicinal Plants: Britain’s home-grown wartime allies): https://www.pharmaceutical-journal.com/opinion/blogs/medicinal-plants-britains-home-grown-wartime-allies/20202796.blog?firstPass=false [accessed: 12.11.19]

[ix] For more information on Pliny the Elder: https://www.britannica.com/biography/Pliny-the-Elder