This section is from the book "The Gardener V2", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
The inmates of this structure will have been kept dry at the root throughout the late severe weather, and their pots protected at the same time from severe frost by being plunged or covered with some dry litter. In those days of cheap boilers and cement jointings the expense of keeping frost from such structures is trifling, while many ends are gained by having them heated in winter, and all risks of injured blossoms by sudden severe frosts further on in the season avoided. The trees in winter can be stowed away closely at one end of the house, and flower-garden plants wintered in the rest of it; or it may be used for wintering Lettuce, etc. The trees should early in February be topdressed with a mixture of loam and horse-droppings in equal proportions, and be plunged in the positions in which they are to stand for the season, giving all that are dry sufficient water to moisten their balls. In plunging them see that the bottoms of the pots stand so that water can freely escape from them. Apricots, Pears, Peaches, etc. etc, will soon be on the move if the weather be mild; and where it is desirable to force them gently, let it be very gently, for the present, simply applying heat to keep the temperature from falling below 45°. In unheated houses it is best to keep the trees back in most localities, for if brought early into bloom the danger from severe late frosts can never be left out of the count; hence it is desirable to heat.