Roses: Their History, Development and Cultivation (1920)
Burnt Earth
J. H. Pemberton

Burnt Earth is within the reach of every one, and a good supply should always be at hand. Apart from any manurial value, it is invaluable for sprinkling among the roots, especially when at the time of planting the soil has a tendency to become wet and heavy, for friable earth of some sort should always lie close around the roots. When we speak of burnt earth we do not mean that hard red substance called "ballast" or baked clay, but friable black earth—it may be red when the fire has been fierce—burnt to a powder. To burn a heap of earth properly requires a little care and attention; those who know will, I hope, pardon a few details. Lay a good foundation of straw, twigs, and several logs of wood—stumps of trees split up are useful. After lighting wait until the fire has a good hold of the logs, and then begin by degrees to cover it with dry mould or turf, roots, weeds, and leaf refuse, but do not hurry on the earth or it will put out the fire. After awhile when much heat is engendered completely cover the heap with a layer of earth. And here lies the difficulty; a slow smothered combustion is necessary if the earth is to be burnt to a friable ash, for a fierce fire causes the earth, especially if it is clayey, to bake hard and lumpy. Therefore we must never allow the fire to break through, and so wherever there are fissures and smoke is given out they must at once be covered, for if this is not attended to the fire will soon burn out. As the earth on the top dries rake it down the sides, applying fresh soil in its place, and keeping the heap cone-shaped. The heap should appear to be heating rather than burning, for if a smell arises it is a sure indication of mischief—the heap requires roasting. Little by little, if this method is followed, the heap will gradually increase in size until all has been laid on. A heap well banked up will last for twenty-four hours without further trouble, but it is best looked at night and morning. With attention the heap, once the interior is hot, will continue in this state of smothered combustion for a week or more—the longer the better. It is needless to say that this process should be carried out in the summer.