Nettles can engulf borders and rough ground in a short space of time, competing with garden plants for water and nutrition and giving an uncared-for look. Control of pernicious weeds such as nettles is challenging, but possible.
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.
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 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 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.
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.
- 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
- Neglected areas can be cleared of established nettles by spraying them with a glyphosate-based weedkiller (William Sinclair Nettle Killer or other tough formulations of glyphosate such as Scotts Roundup Ultra 3000, Scotts Tumbleweed, Bayer Garden Super Strength Weedkiller 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
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1a and 4)
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