Difficult Weeds

Weed Key Considerations

Japanese Knotweed (Fallopia Japonica)

  • Highly invasive, particularly problematic near watercourses.
  • Scheduled under the 1981 Wildlife and Countryside Act.
  • Classified as a ‘controlled waste’ requiring licensed landfill disposal.
  • Grows through walls, tarmac and concrete and can reach 3m high by June.
  • Spreads via rhizomes, does not produce viable seed.
  • Rhizomes from one plant can be 2m deep and 7m wide.
  • Fragments of rhizome of only 1cm can produce new plants.
  • Repeated cutting will weaken rhizomes but is generally ineffective on its own.
  • Digging can increase spread unless every piece of root is removed.

Bracken (Pteridum aquilinum)

  • Widely distributed throughout the UK, vast stands in upland areas, but also increasingly found on waste ground.
  • Fronds are poisonous to cattle and horses, harbours disease-carrying ticks and carries carcinogenic spores.
  • Thick stands shade out all other plants.
  • Extensive underground network of two rhizome types makes control difficult.
  • Non frond-bearing, storage rhizomes are not killed by some herbicides.
  • Repeated cutting will weaken rhizomes but is generally ineffective on its own.

Horsetail (Equisetum arvense)

  • A survivor of the pre-historic age, this fern-like plant spreads mainly by extensive underground rhizomes, up to 2m deep. Foliage shoots emerge in May, preceded by spore-bearing shoots in early spring.
  • Prefers moist and shady areas but increasingly found on waste ground and non-cropped areas where it survives most herbicide treatments and takes over in the absence of competition from other weeds.
  • Poisonous to livestock, but avoided by grazing animals - must be excluded from hay/haylage or silage.
  • Thick waxy cuticle and small needle-like leaves make it difficult to get sufficient spray into the plant to kill the roots.
  • Repeated cutting will weaken rhizomes but is generally ineffective on its own.
  • Some residual herbicides are very effective but cannot be used near desirable species or near water.
  • Generally considered not to be susceptible to glyphosate, but in many areas residuals will not be suitable and it may be the only environmentally acceptable choice.

Ivy (Hedera helix)

  • A shade loving creeping or climbing evergreen plant which can cause damage to masonry in buildings and walls as well as climbing trees and blocking light.
  • Creeping along the ground it can out-compete many desirable plants in ornamental plantings.
  • The thick, waxy cuticle which covers the leaf makes it difficult to penetrate with foliar herbicides and it is generally considered not to be susceptible to glyphosate.
  • In many areas residuals will not be suitable, especially near water and it may be the only environmentally acceptable choice.

Rhododendron (Rhododendron ponticum)

  • A shade loving invasive plant of woodlands, excluding native species from woodland floors.
  • The sheer physical size of the plant, up to 8m in places, together with a tough waxy leaf make Rhododendron difficult to control.
  • It regenerates quickly if not completely killed.

Brambles (Rubus fruticosus)

  • Scrambling perennial of hedgerows and waste ground, can be very invasive, with spiny stems posing a hazard to people and pets in public areas.
  • Spreads both by rhizomes and stems rooting where they come into contact with the ground.
  • Large stands can be difficult to reach over with a sprayer unless an extending lance is used.
  • Insufficient herbicide will reach the roots and re-growth is more likely when:
    • Leaf area is small relative to rootstock and sap is rising strongly early in the spring
    • As soon as fruits appear the leaf growth becomes less vigorous and prone to disease, spraying once this occurs may limit the long-term effectiveness

Giant Hogweed (Heracleum mantegazzianum)

  • Giant version of common hedgerow and pasture weed, growing upto 5m tall, with flowers up to 0.5 metre and leaves 1 metre across.
  • Serious invasive alien, often found near watercourses.
  • It is an offence under the 1981 Wildlife and Countryside Act to plant or cause it grow in the wild.
  • Poisonous sap causes photo sensitive skin irritation and precludes manual methods of removal.
  • Up to 50,000 seeds per plant viable for 15 years mean it can spread rapidly.
  • Fully mature, flowering plant is too tall to spray except with long lances.

Common Ragwort (Senecio jacobaea)

  • Bright yellow flowers prominent on light land, in neglected pasture and waste ground in summer.
  • Mostly spread by seed blown in the wind from neighbouring land.
  • Poisonous to livestock, especially horses, both fresh and in hay or silage.
  • Classified as an injurious weed under the Weeds Act 1959. Landowners should adhere to The Ragwort Code of Practice.
  • Cutting can weaken plants, but may turn them from biennials into perennials.
  • Dead foliage must be removed or have completely died down before livestock can return to treated areas.

Bindweed (Calystegia spp, Convolvulus arvensis)

  • Climbing perennials widespread over hedges, industrial and amenity areas and waste ground.
  • Spread mainly by long underground rhizomes.
  • Tiny fragments of broken roots will regenerate and spread, so digging can cause rapid multiplication.

Ground Elder (Aegopodium podagraria)

  • Deep-rooted, perennial invading disturbed ground and amenity areas, particularly prone to infest ornamental plantings.
  • Spread mainly by long underground rhizomes.
  • Digging can cause rapid multiplication, due to the brittle nature of the roots and the rapid regeneration from the tiniest of fragments.