ABSTRACT
The hot-pipe system is designed to operate during the late autumn, winter or early spring months, though cold storage of scion wood and rootstocks would permit some extension of use. It depends upon a small, well-insulated, closed, heated space sited within a contained area holding a suitable laying-in material for the roots of bare-root grafts, or to provide a bed for holding root-balls of potted or de-potted rootstocks. The heating chamber is designed to enclose only the graft union and makes it possible to provide optimum temperatures for graft union development. Extruded polystyrene has among the highest insulation properties of the commonly available materials*, and is so water resistant that it can be used as a float for control valves in water tanks. Good heat retention is further guaranteed by generous amounts of insulating foam at the meeting edges, with sufficient weight on the upper channel to ensure tight closure.
