No abstract

The Princess of Wales Conservatory at Kew provides an ideal growing environment for many of Kew's tropical and temperate fern collections. The following article deals with the tropical ferns only. These are housed in 'zone 4' at the northern end ofthe building. The planting area is on four different levels, including three elevated concrete decks. The use of raised edging to the pathways and sandstone boulders gives a suitable but limited planting depth in most areas.Drains were built into each floor, with access water being piped away to the lowest level. A two-inch layer of 'Hydroleca' (expanded clay granules) was laid over the concrete base for rapid dispersal of drainage water. This was covered with a layer of 'Teram' (a thin porous material) to prevent the compost washing away and fouling the drainage.The initial compost used was a mixture ofloam, leaf-mould, bark, peat and grit, which provided a well-drained and open planting medium. It should be noted that with conservation of peatlands in mind, the use of sphagnum moss peat is being phased out and substitutes sought. The Fern Unit's use of peat has already fallen by nearly 70 per cent, and when trials of substitutes carried out in the fern conservatory are satisfactory, the use of moss peat will be discontinued. Substitutes are being tested within various nurseries and at Kew, but it is important, of course, for trials also to be carried out in a landscape situation.The concrete wall housing the boiler flues to the east side posed a particular problem. For safety reasons, amongst others, it was decided to construct a rock face from fibreglass over which water could run. Moulds were made on site using the sandstone boulders as models. The finished rock casts were built into a mock 'cliff or 'waterfall' seven metres high by attaching them to a wooden frame which was, in turn, bolted to the concrete wall. To ensure a leakproofflow ofwater it was necessary to seal a channel down the rocks. Many car repair kits and umpteen trials later, the desired effect was achieved. The pool at the base of the fall, which supplies the water,