Is it a nettle or a dead-nettle?
By The Weed GuyLast updated
A dead-nettle does not sting, and it is not a nettle. It is a Lamium, a mint-family plant that borrows the nettle leaf shape and none of the hairs that go with it. The reliable tell is the flower. A stinging nettle carries tiny green ones in drooping tassels from the leaf joints. A dead-nettle carries obvious hooded, two-lipped flowers in whorls up the stem, white on one species and pinkish-red on the other. And ignore the square-stem test. Both plants have square stems.
That last point is worth labouring, because the square stem is the tip you will read everywhere, and it separates nothing at all. NatureSpot's species account for common nettle describes it plainly as having square stems, with leaves armed with stinging hairs. The Wildlife Trusts describe red dead-nettle as having reddish, square stems. Two square-stemmed plants. If you have already run that test and walked away confident, go and look again.
What does work, from a safe distance, is the surface of the leaf and the stem. A stinging nettle is bristly, and those bristles are the whole point of it: the Botanical Society's account describes the stinging hairs as slender tapering needles made of silica, mixed in among ordinary non-stinging hairs on both the leaves and the stems. A dead-nettle is softly hairy or downy all over and has no needles anywhere on it. Put that together with the flower and you have your answer in a few seconds without touching anything, which is how I would rather you did it.
The reason a dead-nettle is built the way it is comes down to family. Lamium sits in the Lamiaceae, the mint family, and a square stem is a family habit rather than a nettle-versus-dead-nettle giveaway. So is the smell, which is the other test worth having: crush a dead-nettle leaf and it is faintly aromatic, where a nettle gives you nothing. So are the hooded, two-lipped flowers arranged in whorls, which are a mint-family shape built for bees to land on. The stinging nettle is in a different family altogether and only resembles one from ten feet away.
Which dead-nettle is it, and why two of them are the same plant
Three of them turn up in British gardens, and the search terms treat them as more different than they are. Start with the one that behaves least like a weed. White dead-nettle, Lamium album, is a perennial: short to medium, faintly aromatic, patch-forming and stoloniferous, meaning it creeps along the surface on stems that root as they go. It reaches up to 80cm. The flowers are white, hooded and 20 to 25mm long, sitting in whorls up the stem among heart-shaped, deeply toothed leaves. The flowering window is unusually long and the sources differ slightly on it: NatureSpot gives April to November, the Wildlife Trusts March to December.
Red dead-nettle, Lamium purpureum, is a different proposition. It is an annual, roughly half the size at up to 30cm, sprawling rather than standing upright, with reddish square stems and pinkish-red hooded flowers 10 to 18mm long. Garden Organic gives its flowering as March to October and sometimes on into the winter. The upper leaves and the bracts around the flower head go distinctly purple, which is what you actually notice first: a low purple haze over a bare vegetable bed in March, before anything else has got going.
Now the part that explains two of the biggest search terms on this subject. Red dead-nettle and purple dead-nettle are the same plant. GBIF lists both red deadnettle and purple deadnettle as vernacular names against the same taxon, Lamium purpureum, and every British source I read uses red: the Wildlife Trusts, NatureSpot and First Nature all call it red dead-nettle. Purple is the name that comes over from North America. So if you are comparing two pages and one describes red while the other describes purple, you are reading about one plant twice.
The third one is genuinely different, and it is the one people actually misidentify. Henbit dead-nettle, Lamium amplexicaule, is close to red dead-nettle at a glance: same low sprawling habit, same pinkish-purple hooded flowers at 14 to 20mm. The tell is where the leaves meet the stem. NatureSpot describes henbit's upper leaves as unstalked and half clasping the stem, where every leaf on a red dead-nettle is stalked. One look at the leaf joint under the flower head settles it. And if the leaves under the flower head are deeply cut rather than simply toothed, First Nature points you at cut-leaved dead-nettle, Lamium hybridum, instead, because red dead-nettle's are serrate or crenate but never deeply cut.
What the answer changes about getting rid of it
This is why the thirty seconds is worth spending. A stinging nettle is a perennial sitting on a shallow mat of bright yellow rhizome, and taking the tops off it is exactly what the plant is built to survive, which is the whole argument of my page on getting rid of nettles. Neither dead-nettle needs that programme. And the two dead-nettles do not need the same treatment as each other, which is the bit that gets flattened whenever they are mentioned in one breath.
Red dead-nettle is an annual, so pulling or hoeing genuinely finishes that plant. There is one caveat the tidy version of this advice leaves out, and it comes off Garden Organic's weed datasheet: in moist conditions, detached shoots can re-root after spring cultivation. So hoe it on a dry day, and rake the debris off rather than leaving it lying on damp soil, or you have propagated the thing you just removed. Henbit is an annual too and takes exactly the same handling.
White dead-nettle is the perennial, and it behaves like a much politer version of its stinging namesake. It creeps by stolons and forms a patch, so whatever you leave in the ground carries on growing. Pulling works if you get the creeping stems up with the plant rather than snapping them off. A systemic weedkiller works for the same reason it works on a nettle, by travelling to the part of the plant you cannot reach with a fork. But keep the scale in proportion before you reach for anything: white dead-nettle tops out around 80cm, where a stinging nettle typically makes a metre and can reach two, and there is no yellow rhizome core underneath it.
Why the annual one keeps coming back anyway
Because of what is already in the soil. Garden Organic's datasheet puts red dead-nettle at 27,634 seeds from a single plant, dropping from May to July and on into November, with a plant competing against a winter wheat crop still managing somewhere between 1,075 and 4,594. Seedlings then emerge mainly in March to May and again from July to October, so one summer's seeding gives you two flushes the following year.
The numbers that matter more are the ones about how long that seed lasts. The same datasheet records a mean annual decline of 20% in field soil, which puts the estimated time to a 95% decline at 13 to 14 years, and notes that seed recovered from excavations and dated at 30 years old has been reported to germinate. Henbit is in the same territory: about 1,000 seeds a plant, and viable in field soil for 25 years. Clearing every plant you can see does not clear the ground, and it will not for a very long time, which is the honest answer to why it is back next March after you did a proper job on it.
There is one lever, and it is in the same document. Light is required for germination. Red dead-nettle seed sitting in the dark stays where it is. That is the entire argument for covering bare soil instead of weeding it over and over, and it is why a mulch or a membrane earns its place on a bed that produces a purple haze every spring, which I have set out separately on the weed membranes page. On a stinging nettle the job is to kill the root or it comes back. On a dead-nettle the root was never the problem. The seed bank is, so stop it getting its light.