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Lamium purpureum, the Red Dead-nettle, is a real commoner; it occurs in all parts of Britain and Ireland up to 610 metres above sea level, and throughout Europe. To most people it is merely a garden ‘weed’ to be removed with a stroke of the hoe. It is even more common than its close relative Lamium album the White Dead Nettle which we recently covered in this blog. L. album is a perennial with white flowers whilst L. purpureum is an annual with pinkish-purple flowers. Both are now considered to be ‘archaeophytes’. These are plants that are not native but have been here for a very long time, often defined as before the year 1492 when Christopher Columbus arrived in the New World.
I have found numerous English names for this plant: Badman’s Posies, Day Nettle, Deaf Nettle, Dog Nettle, Purple Deadnettle, Rabbit Meat deadnettle, Red Archangel, Red Henbit, Bumblebee Flower. Fortunately, it has only one Latin name, the one which Linnaeus gave it, Lamium purpureum.
The Dead-nettles all belong to the large family Lamiaceae and are unrelated to Stinging- nettles. Dead-nettles never sting and their flowers are entirely different from Stinging-nettles. If you are new to botany you can see the family features of the Lamiaceae on our LEARN page. Nearly all its members have stems that are square in cross-section, leaves that are arranged in opposite pairs and flowers that are zygomorphic (bilaterally symmetrical). The family serves us well; it contains many useful species including mints, salvias, lavender, rosemary and thyme. All are rich in volatile oils.
The flowers of L. purpureum form from a straight corolla tube (see a pair of them in the image above). They develop to have a hooded upper lip and a two-lobed lower lip. The lower lip is a convenient landing platform for pollinating insects. The main pollinators of both Lamium purpureum and L. album are wild bees (bumblebees and solitary bees). Among foraging insects the participation of honey bees Apis mellifera was 35% for Lamium purpureum and 11.9 % for L. album in one study. Bees come for the nectar at times of year when flowers are scarce and they like to harvest pollen in the spring when they need protein.
The stems of the plant can form roots when in contact with the ground. It may happen in late winter when the plant is pressed down by snow. Then, a multi-stemmed clump forms. Each plant of L. purpureum is usually about 20 cm tall, somewhat branched, and may produce more than 1000 seeds. These seeds have peculiar sticky attachments called alaiosomes to facilitate dispersal by ants (you can just see one in the painting above, bottom-left-hand corner. Elaiosomes are nutritious fatty structures attractive to ants. The ant carries the seed to its nest and the elaiosome is fed to the hungry larvae. Many weed species have them (Pemberton and Irvine 1990).
The leaves are softly hairy, not as large as in the White Dead-nettle (typically 2-3 cm) You can see their shape in the picture above. These leaves are less pointed than those of L. album.
Books tell us that flowering begins in March, but we have seen many plants in flower much earlier. L. purpureum featured on our list of New Year flowers a few weeks ago, and I’ve just scanned the last six years of results from the very much larger New Year Plant Hunt of the Botanical Society of Britain and Ireland. L. purpureum has always been in the top ten species most seen in early January. I believe these are the flowers of plants that germinated back in the Autumn and developed strongly in early winter, not minding the cold.
In winter the leaves are green. In the summer they develop purple-red pigmentation, especially in the youngest leaves. Quite many species do this, presumably as a means of protecting their photosystems from strong sunlight. Purple pigmentation in plants is usually anthocyanin, a water-soluble substance that it found in the cell’s vacuoles, especially the epidermis. It absorbs blue, green and red light, and provides protection for the photosynthetic machinery. Plants make it when the sun shines brightly, just as we slap protective oils on our skin before going to the beach. At least, that is what I believed before writing this blog but my literature search has turned up a newly-published paper in a highly reputable journal that casts doubt on the story (Agati et al 2021). Warning: don’t look at this reference unless you are a plant physiologist – it’s heavy-going.
Red Dead-nettle is a ruderal species. The word ruderal is an interesting one, coming from rudus the Latin for rubble. Dictionaries have various definitions such as ‘a plant growing in waste places, along roadsides or in rubbish’, or ‘a plant that is associated with human dwellings or agriculture, or one that colonizes waste ground’. Its use in plant ecology was advanced by J. Philip Grime of the University of Sheffield in 1977. Grime proposed a functional classification of plants based on what he called ‘strategies’. This caused a stir in some quarters – many scholars didn’t like the idea of plants having strategies as it suggests ‘an intelligent purpose’ which only humans can have. However, the ideas were embraced in North America where no-one expressed such qualms. According to Grime and his colleagues, plants have a combination of ‘traits’ that makes them competitive (C), stress-tolerant (S), ruderal (R) or more usually somewhere in between the three. Later his group attempted to score these traits, based on experimental and observational data, and they found that L. purpureum was among the most ruderal of all species (Grime, Hodgson and Hunt 1988). It thrives in disturbed places, produces plenty of seeds, and is often associated with human dwellings – it’s an urban specialist. Grime’s evolutionary theory of plant traits , dubbed CSR theory, has often been challenged but has withstood the test of time. Sadly, Phil Grime died last year. He was the most productive British plant ecologist of his generation.
As with many plant species, there are others you may mistake for this one. The one you are most likely to see, and which occupies the same sorts of ruderal habitat, is Lamium amplexicaule, called Henbit because it looks as though the leaf edges have been pecked by hens (see below). Notice how its flowers stick up proudly, quite unlike L. purpureum. You might even see a white mutant of L. purpureum (see below) and think it’s the White Dead-nettle. There are three other Lamiums, but they are rather rare. You might also encounter Wild Basil, Clinopodium vulgare. Disappointingly, it doesn’t smell or taste like cultivated Basil.
Botanical foragers speak highly of the young leaves of Lamium purpureum, recommending their use in salad. Myself, I don’t fancy the raw leaves as food – too hairy. I might try them to add interest in omlettes. Herbalists through the ages have believed the species to be efficacious for many complaints. We are told the dried leaves have been used as a poultice to stop bleeding whilst the fresh bruised leaves can be applied to external cuts and wounds. The leaves may also be made into a tea and drunk to promote perspiration and discharge from the kidneys in the treatment of chills. I must admit to having difficulty with old-fashioned herbal words. Do we still believe there is such a thing as a ‘chill’ ?
References
Grime JP (1977) Evidence for the existence of three primary strategies in plants and its relevance to ecological and evolutionary theory. American Naturalist 111, 1169–1194.
Grime JP, Hodgson JG and Hunt R (1988) Comparative Plant Ecology; a Functional Approach. Unwin Hyman.
Pemberton RW & Irving DW (1990) Elaiosomes on weed seeds and the potential for myrmecochory in naturalized plants. Weed Science 38, 615-619.
John Grace
Botany in Scotland 
Wonderfully detailed
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