All weed species to some extent can cause crop yield reductions and quality downgrade in both horticultural and agricultural systems. Perennial weeds are extremely challenging to control
in organic systems, as often the increased element of cultural techniques can increase the spread of perennial species. Perennial weeds compete with the main crop for water, nutrients and light and are often more effective in using available moisture than the crop resulting in limitations to the crop production. Controlling perennial weeds is more costly and time consuming than annual weed control and in some cases might affect the crop rotation.
For most horticultural crops controlling perennial weeds prior to planting or drilling is easier rather than within the crop. For effective control an understanding of individual species biology and persistence will help to maximise control by manipulating weaker spots in their lifecycle. A range of control options are available including mechanical weeding, allelopathy, electrical weeding, cover cropping, cutting and mowing, but all vary depending on weed species and density present. With new technology and novel ideas, control options are becoming more diverse and an integrated weed management approach is always advisable.