Red Dead-Nettle

Lamium purpureum

A dull looking weed, perhaps, but of infinite interest: lacking, no doubt in beauty, but rich in skilful plans, the Red Dead Nettle challenges us to ignore it at our loss.

G Clarke Nuttall. Wild Flowers As They Grow 1912

Red dead-nettle 

Dead-nettles

Dead-nettles belong to the family Lamiaceae (old name Labiateae). Dead-nettle is an appropriate name because the leaves look distinctly 'nettley' and when I was a child I treated dead-nettles with the same suspicion I treated nettles. The precautionary principle applied and if a ball went into nettles or dead-nettles someone else could go and get it.
The general features of dead-nettles are square stems that are as easily felt as seen. The leaves are simple and oppositely arranged. The leaf margins are toothed resulting in a nettle-like appearance. Usually, successive pairs of leaves are at right angles to each other up the stem (decurrent).
The flowers are arranged in successive whorls up the stem usually above pairs of leaves or bracts.
The structure of the flowers is quite distinct from the open radial arrangement we saw in the previous blog entries describing buttercups and marsh-marigolds. The 5 sepals are fused into a bell-shaped structure with 5 pointed teeth. After fertilisation, the corolla drops off leaving behind a 5 pointed calyx with the ovary at the bottom.
The 5 petals are fused to form a tube with 2 fold or mirror symmetry.  There are usually two lips, the upper is larger and overhanging and the lower has two lobes - see picture above.
There are 4 stamens -2 long and 2 short- that are concealed within the upper lip of the corolla tube.
If you look closely within the upper lip in more mature flowers you can also see the style ending in a bifid stigma.
Tracing the style back to its origin you encounter a superior ovary that really has two lobes but resembles a hot-cross bun; these are the four nutlets. This combination of a square stem and 4 nutlets is diagnostic of the Lamiaceae.
In Leazes Park there 3 species of dead-nettle to be found at the moment (mid-April) they are white dead-nettle Lamium album, red dead-nettle Lamium purpureum, and yellow archangel Lamiastrum galeobdolon. The name yellow archangel is intriguing and the plant will be discussed in a future blog. In fact, all three of these plants were formerly called archangel. That is red-archangel, white-archangel and of course yellow. The reasons for this are not clear or why the name has only persisted for yellow-archangel.

Red dead-nettle

Red dead-nettle conforms to the general particulars of dead nettles but it is smaller than white dead-nettle or yellow archangel. The flowers are more purple than red and the North American name of purple dead-nettle is more accurate. In poor soils or exposed to atmospheric pollution the leaves, particularly the upper ones, often take on a red colour.
The leaves are somewhat heart-shaped and all have short stalks (petioles). This helps to distinguish red dead-nettle from henbit dead-nettle that also has purple flowers. In the case of henbit dead-nettle, the leaves are sessile that is they join directly to the stem without a petiole. Unlike white dead-nettle or yellow archangel, the leaves tend to be crowded together at the top of the stem in the case of red dead-nettle.
The calyx has long pointed teeth that are fringed with purple and with magnification its hairs are visible.
Although viewed from above the flowers are an even delicate pink/purple, if you get down on your hands and knees exquisite marking can be seen on the lower lip. To me, these are the equal of the orchids, notwithstanding the commonplace nature of the flower.

Red dead-nettle as seen from a low angle . The long corolla tube is not so visible when viewed
from above. Note the markings on the lower lip and the anthers under the upper lip. A
five-pointed calyx without the corolla tube can be seen lower centre.

 Five-pointed calyx tube. At the bottom of the tube four nutlets.

Side view showing square stem and long corolla tubes

Stamens visible within the concavity of the upper lip

Bifid stigma is just visible at the entrance to corolla tube.

Pollination 

In comparison to flowers with an open arrangement of flower parts such as buttercups, red dead-nettle is dependent on a specialist courier to transport pollen between flowers.  To reach the nectar at the base of the corolla tube requires a proboscis that can reach to the bottom and a body small enough to enter the flower - something along the lines of a honey bee or mason bee. However, this raises the question of why it tends to remain in flower all year round including times when there are no honey-bees to be found.
A bee entering the flower will get pollen on its back that it will transfer to the next flower. The risk of self pollination is reduced by male and female sex parts in the same flower maturing at different times. It appears to me that the anthers mature first and the bifid stigma only becomes visible later. An arrangement that is termed protandry.

When and where to find red-dead nettle

You can find red dead-nettle in flower most of the year and it is always a good bet for New-Year plant hunts when there is little else around. The only thing that seems to knock it back for a while is a succession of severe frosts and even then it seems to get going again much quicker than most plants.

It is to be found most areas of the park though you seldom see it growing to its maximum height.  It likes recently disturbed ground and seems to be one of the first things to come back by the side of paths that have been sprayed with weed killer.