Nettles as weeds

Nettles are a valuable food plant for British butterflies and have several herbal uses. But they can also engulf borders and rough ground in a short space of time, compete with garden plants and pose a risk from their stinging hairs. For these reasons some gardeners may wish to keep them in check. 

Nettles

Quick facts

Common name Nettle
Botanical name Urtica dioica, U. urens
Areas affected Many, including newly cultivated soil, especially where phosphate levels are high
Main causes Nettles germinate easily from seeds
Timing Seen and treated spring to autumn

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. Seed-eating birds, including bullfinches, serins and siskins, benefit from nettles that have been left to go to seed.

Nettles are also useful for gardeners wishing to make their own high nitrogen liquid fertiliser. 

Despite the many benefits of nettles, they may not be welcome in all areas of a garden. This page looks at options for gardeners when nettles are becoming a problem.

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 RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner. 

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. 

Cultural 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 Weedout Extra Tough 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  
When using glyphosate take care to avoid leaves and other green parts of all garden plants as it is not selective in action. Used with care, glyphosate is safe to use around the base of non-suckering woody plants, as long as the bark is woody, brown and mature. Glyphosate is not active through the soil and there is therefore no risk garden plants will absorb it through their roots.

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.

Downloads

Weadkillers for Home Gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1a and 4)

Links

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

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