Perennial weeds can be difficult to eradicate from soils. The majority have the ability to grow from very small sections of rhizome (underground stem sections) which can be deep and inaccessible.
Main culprits
Bellbind (Calystegia sepium)
Bindweed (Convolvulus arvensis)
Bracken (Pteridium aquilinum)
Ground elder (Aegopodium podagraria)
Horsetail (Equisetum arvense)
Japanese knotweed
(Fallopia japonica) (illustrated right)
Cultural control
Removing foliage: Repeatedly cutting down foliage provides temporary control, but new growth quickly regenerates from the rhizome which contains large food reserves. It will eventually weaken plants, but this takes several years.
Digging: Digging out roots will provide effective control for ground elder, as the rhizomes don’t penetrate too deeply. Removal must be thorough, otherwise sections remaining in the soil will quickly regenerate. For plants such as Japanese knotweed, bindweed and horsetail, where roots can penetrate for many metres, digging only offers a temporary solution.
Smothering:
Ground elder (illustrated left) can be effectively controlled
by smothering. Covering the site with old carpet or black
polythene gradually weakens the plant. It takes several years
to substantially reduce a colony.
Chemical control
Glyphosate: (e.g. Roundup or Tumbleweed) This total weedkiller is applied to the foliage, where it is then translocated throughout the weed. Being non-selective it’s essential to avoid spray drift. For maximum effect weed growth should be well advanced.
Dichlobenil: (e.g. Casoron G4 Weed Barrier) This residual weedkiller can only be used on non-crop areas (including paths) or among most woody species that are well established.
When using such chemicals always follow the manufacturer’s instructions.
Further information
A Conservation and Environment leaflet on the use of garden chemicals is available.