MY childhood playground on the North York Moors was covered with bracken, a tall and resilient fern-like plant.

With my pals, I would play hide-and-seek or hunt Robin Hood among the tall plants. We would build shelters and fashion their walls and roofs from the foliage, weaving them into the standing stems.

It was good fun, but now I know that bracken could be dangerous to children, animals and other plants. When we cheerfully played among it, the only concerns were that we might cut our hands if they slipped on the stems as we tried to uproot them.

Bracken is a type of hardy fern that is sometimes used in domestic gardens as background on a rockery but it is difficult to prevent it spreading into areas where it is unwanted.

It is this ability to spread out of control that has made it detested. As it spreads, it destroys all other vegetation and it has been described as public enemy number one, a deadly weed and a poison fern.

The dangers it presents are said to be numerous and because it spreads through the use of spores. There is a suggestion that prolonged exposure to bracken can lead to cancer in humans.

Advice is widely presented to ramblers and hikers to keep well away from bracken, particularly during the summer when the spores can be airborne. It seems that short exposure does not present such a problem.

There is no doubt the plant is dangerous to sheep. If they eat it, it can poison their system to such an extent that it can be fatal, while if they survive, they might go blind.

Up on the North York Moors and within the Yorkshire Dales there have been reports of sheep becoming blind during a summer upon the moors whereas those on lower ground were not afflicted.

A sheep blinded in this way will move with the flock but cannot travel alone, even when herded by a sheepdog.

The eating of bracken also causes cancer to their jaws and may destroy the white cells in their blood. That ruins their immunity system so that they are liable to other diseases.

In dense bracken, aggressive ticks may proliferate and these can affect humans, sheep and grouse, causing irritation at least and death on occasions.

For the grouse, bracken is doubly dangerous because it can destroy the heather upon which the grouse population entirely depends.

One problem on the moors is that bracken can rapidly establish itself upon patches where the heather has been accidentally burned off, as when a moor fire starts through carelessness.

When controlled burning occurs, efforts are made to prevent the spread of bracken, but the new fronds grow with surprising speed and energy by spreading underground.

One report said that heather was encroaching upon 500 acres of moorland every year and if nothing is done to stop it, it will eradicate the heather. That will lead to the extinction of the grouse population. It will also kill any other plant that stands in its way.

The problem is how to prevent the non-stop spread of this troublesome fern, considered to be the one of the hardiest plants on earth.

Burning is not the answer because the spores can survive in burnt areas to produce long stems that grow underground to provide an even thicker patch of bracken – indeed, burning makes it thrive.

Pesticides and herbicides cannot be used because they damage other plants and thus destroy the habitat of insects, birds and animals, whilst attempts to physically clear the land of bracken is both expensive and time consuming.

Despite efforts to eradicate it from the moors, it continues to spread at a rate of around three per cent a year. In recent years, it was hoped that a South African caterpillar with a voracious appetite for bracken fronds might be the answer, but one technique is to use a heavy roller to crush the stems so the plant cannot gain the necessary nourishment.

But using such a device on the moors is far from easy due to the boulders that lie hidden deep in the bracken, and of course, the gradients.

One theory is that it could be harvested – after all, bracken was formerly used as bedding for livestock and its ashes have been used to make glass, soap and bricks.

It was also used to thatch barns and cottages, but one theory raises the question of whether it could it be collected and used as a compost. Is this an entire new industry waiting to be brought to life?