Gunneras planted in half barrels either side of the bench

I love gunneras but never grown succesfully, is there a special thing you do to these pots perhaps to keep them damp ? I recently found a tag by the pond with gunnera on it, reminded me I think I put one there about 6 years ago.

Well my Gunneras are both in large half barrels but the natural and most successful way of growing them is by the side of a pond in the more boggy area which is consistently damp but not water-logged. Alan Titchmarsh demonstrated a way of planting gunneras on one of his programs. Dig a large hole at least 18" deep by the side of your existing pond but not running into it so the water can only drain in if the pond overflows, line with butyl and fill with a mixture of JI no 3 and compost, plant the Gunnera and it should take off. The butyl will prevent the soil from drying out and the water from draining away. Make sure it is in a sunny/part sunny position and you should get a marvellous specimen each year. For overwintering, cut back the majority of the leaves and keep some of the large ones to cover over the top of the plant which is protruding above the soil, mulch around it with bark chippings and his should protect it from the frost.