For Pip Webster, it’s a nuisance but butterflies and caterpillars thrive on it
Nettles are a nuisance, especially when trying to moor, but they are a home to some
Most of us know to our cost that both the round stem and the leaves of nettles are armed with vicious stings. Brittle poison-filled hairs snap and act like small hypodermic needles when just brushed against, releasing venom into the skin.
According to our ancestors, the sting protected you against sorcery, but if you want to harvest them safely, just pluck up your courage and ‘grasp the nettle’.
Under firm pressure the hairs bend back harmlessly or so it is claimed – I find myself reluctant to experiment.
You can then weave nettles stems into fabric, and the iron-rich leaves, that lose their sting when cooked, can be consumed in nettle soup and tea.
Stinging nettles grow in areas where phosphate levels are high, as often occurs in areas previously disturbed by man. Most of the nettles you will see growing along the towpath are the common perennial type (Urtica dioica) that can reach about 1.5m high and bear clusters of tiny male and female greenish-white flowers on separate plants.
Female flowers are long and pendulous while male flowers stick out at right-angles from the stem in the leaf axils. Being wind-pollinated, the flowers have not had to evolve into flamboyant blooms to attract insects.
The sting of the rarer annual nettle (Urtica urens) is not quite so vicious. This smaller plant (30cm) has more rounded and deeply
toothed leaves than the common or stinging nettle and it is monoecious – both male and female flowers are borne on the same plant. Tiny and greenish, the flowers appear in compact clusters in the leaf axils. Both species flower from June through to autumn.
The traditional remedy for being nettled is to rub the affected area with a dock leaf – and I can vouch for the efficacy. It is uncertain whether the relief comes from a chemical component or just from the cooling effect of the sap released from the crushed leaf. Fortunately docks often grow in the same habitats as nettles and any of the many species and hybrids of dock found in this country – they are notoriously difficult to distinguish – will do.
Stinging hairs evolved as a successful defence against grazing animals, so any insects living on the nettles are also unlikely to end up in a herbivore’s stomach. Small insects can move between the spines on the nettle without activating the sting, so nettles are the favoured food plant for the larvae of some of our most beautiful butterflies, including the ‘nettle fly’.
Better known today as the Red Admiral (a corruption of Red Admirable), this handsome butterfly can be seen out at sea, albeit on the wing.
A major influx of migrants from Africa and southern Europe arrive on our island in late May and June and work their way northwards, joining the increasing number of resident butterflies that are able to survive our milder winters. Vivid markings in velvet black, scarlet and white distinguish one of the largest British butterflies.
Females lay single small, green eggs on the upper surface of young stinging nettle leaves. Spiny caterpillars hatch after seven days; the black and yellow-green colour forms both have yellow markings down each flank.
Each caterpillar spins a small tent from a fold at the base of the leaf where it remains hidden throughout its life, enlarging its hideout as it grows until pupating, hanging in a nettle tent.
The caterpillars of the Red Admiral’s cousins, the Peacock and Small Tortoiseshell, are more gregarious and easier to spot. The eggs of both of these species are laid in dense clusters on the underside of leaves and the young, spiny caterpillars feed in untidy webs spun over the nettle tops before dispersing when fully grown.
The protective web canopy is spun by the caterpillars themselves and is distasteful to predatory birds. So don’t slash all of those nasty nettles down – somebody loves them.