The Control of Bracken
Bracken is now a menace, because over the last century it has hugely increased its coverage of heather and pasture, and because it continues its increase exponentially. A hundred years ago, many villagers were pig owners or small scale stockmen, who cut bracken for animal bedding, and for whom access to choice bracken beds was competetive. The areas nearest to the villages may well have been cut twice (annually), and it is thought that this cutting once kept it under control. Other reasons for its most recent spreading could be the ability of the plant to fix nitrogen from a polluted atmosphere, or its use of higher fertility levels (from larger sheep flocks).
All manner of mechanical means have been tried to tame it during the last 50 years, and yet there still remain areas of disagreement. Some scientists advocate crushing the fronds in late July, others advocate 2 cuts each year, while still others, suggest only one late cut. The truth is that large, long-term experiments with machinery are rare, and that most land-owners use the chemical Asulox to control it. This practice seems likely to continue, despite the expense, and despite the lack of research into many aspects of chemicals short/long term effects (see report of E.P.A.). Of course, bracken itself contains noxious chemicals, and releases carcinogenic spores in August, which means that destroying it by hand or mechanical means, is not always a safe option, and that masks are worth wearing.
On our sheep-stray area of moorland, bracken has been contained by the use of Azulox (in the past). Our current non-chemical strategy mainly involves blade-strimming in late June/July, and repeated hand chiselling in isolated beds. Deep chisel hoeing and hoiking, is much more damaging than cutting (and decreases the shoot numbers), but it needs determined labour & lots of time. Chiselling in long heather can be awkward, so we sometimes resort to pulling the young ferns by hand.
Generally speaking, mechanical mowing or crushing is slow and difficult, and in some awkward areas of terrain, even small-scale crushers are limited to where they can go. The effect of this mechanical work is mostly to contain the problem. If it is relentless, then less foliage is produced, and spreading can be controlled. If the foliage of any rhisome plants is damaged often enough, energy levels are weakened, so that repeated attacks in the same season must be more damaging than a single one, in late July. With bracken, this is an opinion that is well supported by other peoples research.