How are perennial weeds, such as thistles and docks, controlled?
As all herbicides are prohibited in organic systems weed control must be achieved by management practices and mechanical methods.
The key approach is to consider what conditions and environments a particular weed favours – and wherever possible, look to provide the conditions that this weed finds unfavourable!
A good and varied rotation with mixed winter and spring sown crops, sub-soiling and improved drainage, improving overall fertility levels, raising the pH, preventing over-grazing and, where appropriate, repeated cultivations all have their place in making life uncomfortable for key weed species. Do not underestimate the benefits of mixed grazing systems.
For problem weeds, such as docks and creeping thistle, the message is one of an on-going programme of control in an organic system, rather than short-term eradication:
Creeping thistle thrives in fertile, undergrazed pasture but does not survive long on silage land. Repeated topping just before and during flowering in June, certainly before seed set, and again in August should control the problem on permanent pastures. While very labour-intensive, hand-roguing with small teams using specialist tools can significantly reduce problem areas. Do not top or cut too early in the season, or too soon before flowering, as this will simply encourage root development and creeping.
Docks are the most difficult weeds to control in an organic system. A dense, well managed sward will minimise infestation since seedling docks are poor competitors. However, bare soil patches caused by poaching or over-grazing will enable docks to rapidly germinate and establish. Avoid poaching, soil compaction and the over-use of slurry. An effective topping regime to prevent seeding will reduce minor problems in the long-term.
Physically removing problem infestations by hand may be labour intensive but can prevent long-term problems from developing – ask us about the 'Lazy Dog' tool! Again, don't underestimate the benefits of mixed grazing systems. Well-planned crop rotations can also be very effective in controlling docks but a wide range of measures will most probably be necessary.
In the case of severe infestations, and where rotations can be applied, a bastard fallow with repeated cultivations to bring the tap root to the surface may be necessary in early-mid summer.
Under the standards all herbicide use is prohibited, including spot-spraying or weed-wiping.