Bracken(Pteridium aquilinum), is one of the most successful plants in the world. It has the ability, by virtue of its underground rhizomes, to spread considerably. One plant alone can occupy a large area and fragment into separate plants which themselves have similar capacity. During the last fanning depression, in the late 1920s to 1930s, when marginal land was abandoned from cultivation and adequate stocking, bracken crept down the hill to invade what had previously been reasonable upland pasture. At that time, the late Professor Stapledon estimated that well in excess of a fifth of the upland of Wales and Scotland was rendered agriculturally of poor value because of bracken encroachment. No-one knows the total area in the world which this plant occupies; it must be many many millions of hectares, much of which could provide a more useful grazing. It is certainly a successful plant.