What are nettles?

Perennial nettles (Urtica dioica) and the annual nettle (Urtica urens) are usually considered to be weeds, although if you have the space to leave some, they can be an excellent source of food and habitat for butterflies such as the red admiral, peacock and small tortoiseshell.

Appearance

Nettles are hardy perennials that form large clumps up to 1.2m (4ft) in height.

Unlike deadnettles (Lamium), stinging nettles (Urtica) have stinging hairs that make them quickly apparent to the gardener when weeding. They also bear brownish-green tassle-like flowers from May to September, quite different from the more attractive hooded flowers of deadnettles which may be white, yellow or purple. Male and female flowers are on separate plants.

The problem

The perennial stinging nettle (Urtica dioica) is a perennial, herbaceous plant with creeping roots. It is perhaps most troublesome in loose, newly cultivated soil, especially where phosphate levels are high. The creeping surface stems can extend for some considerable distance, rooting at the nodes and producing aerial shoots.

The annual nettle does not have long-lasting roots, but does produce very large numbers of seeds from an early age. Like its perennial realtives, it relishes fertile soils rich in organic matter and is a serious weed in vegetable gardens.

Nettles are very tolerant of extreme climatic conditions, germinating readily from seeds. Individual plants or clumps are either male or female and when both sexes are growing close together female plants produce large numbers of seeds.

Control

The best time to apply weedkillers to nettles is when they are in vigorous growth, but have not yet flowered. Digging up the plants can be done at any time of year. They can be controlled using non-chemical or chemical methods.

Non-weedkiller control

• It is important to prevent stinging nettles, especially the annual nettles, seeding by cutting down plants in mid-summer, or earlier
• In light soils, or where there are isolated clumps, digging out will be effective
• Remove as many of the creeping stems as possible as any piece with a node is capable of producing a new plant
• Digging up the plants can be done at any time of year
• Young seedlings can be destroyed by hoeing
• Perennial nettles are unlikely to be a persistent problem in regularly cultivated areas, except perhaps where there is a residue of seeds in the soil, or the area is adjacent to neglected land. However, annual nettles can be very numerous in cultivated soils
• Nettles cannot withstand repeated mowing

Weedkiller control

• Neglected areas can be cleared of established nettles by spraying them with a glyphosate-based weedkiller (such as Roundup Ultra, SBM Job done Tough Weedkiller (soluble sachet only) or Doff Maxi Strength Glyphosate Weedkiller) which should be applied as a spray in June, shortly before they flower
• A second application may be necessary in September
• Check again in early spring and fork out any surviving roots
• In rough grassland, where glyphosate would kill the grass, use the selective weedkiller Vitax SBK Brushwood Killer which contains triclopyr. Two or three treatments may be needed
• Ensure you follow the directions on the packaging of weedkillers

Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

Links

Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers
Weeds: non-chemical control