This section is from the book "The Gardener V1", 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 soft-wooded varieties of the above rank high as winter and spring blooming plants, and their being almost hardy makes them more valuable. From necessity we had a quantity which stood all last winter in cold frames, where there was no artificial heat. Through all the severest of the frost the covers were never off, and several times, when the glass was falling very low, snow was collected, and laid all over to the depth of several inches. They were more than a month covered up in this way. We were rather afraid to uncover them, and when first looked at everything was quite hard with frost. After careful and gradual exposure, we found that, with the exception of the tips of a few being a little browned, they were not injured. After flowering is over they should be cut down and placed in a cool airy situation till they have broken, when all should be examined; those that require another pot should be attended to at once. The pots ought to be clean and well drained, using good fibry peat, broken up with the hand, to which add a good sprinkling of silver-sand; and when charcoal can be procured, break a little the size of beans, and mix in amongst the whole.
If large plants are required in a short time, the soft-wooded sorts might be placed in a gentle heat; but if small healthy plants are in request for house-decoration, place them in a cold frame, where they can have plenty of air. If a brick can be placed at each corner of the frame, so as to raise it the thickness of the brick, it will allow the air to circulate more freely amongst the plants, keeping the lights close at hand in case of heavy rains. When they are on, let them be tilted alternately back and front. There is scarcely any other class of plants which require more care in watering than Heaths, but if properly attended to in watering, and frequent syringing overhead, by autumn, nice plants with strong flowering-spikes will repay all the summer attention.