Moorland fires in 15-year-old Calluna burnt in the autumn under dry, windy conditions, with 15,900 kg/ha of available fuel were hotter than spring fires in, 25-year-old Calluna burnt under cool, moist conditions with 23,200 kg/ha of available fuel. Weather conditions prevailing at the time of burning are considered the main factors responsible for the poor success of the spring fires. Recommendations are made for the use of back- burning techniques in over-mature heather. Dormant tissue, as indicated by an expression of low relative turgidity, was more heat tolerant than active tissue (high relative turgidity). Norway spruce was more heat tolerant than Japanese larch, which in turn was more heat tolerant than Calluna. The implications of these differential heat tolerances are discussed. Burning and old age (over 15 years) are detri-mental to the vegetative regeneration of Calluna. In the summer, the micro-climate of burnt areas is slightly warmer and drier than unburnt, areas, but the same in winter. Some benefits may accrue to Calluna regeneration on burnt areas. A general discussion is presented on moor burning, physiological heat tolerance, and micro-climate of burnt and unburnt areas.