The Garden Under Glass

266 THE GARDEN UNDER GLASS The Reason for Hardening Off It may be wondered why there should be any necessity for hardening off plants which are of a hardy character or come under the category of hardy plants. Well, the probability is that they have been raised in much heat in order to forward them when progress in plant life outsidc would be so slow as to be almost imperceptible. Having been thus accustomed to a high temperature, it would mean either positive loss or a very certain and severe check to put themstraight away out in inclement orcold weather. It is thus that the hardening off becomes necessary. When plants are hardened off in a correct manner they may be removed by stages from a temperature of not less than 6o° to the outside, where it would sometimes go below freezing point without any perceptible check, and probably with considerable advantage to their Constitution. Some such method is absolutely essential when the plants have to be set outside fairly early in the season. How to Harden Off Plants This is, of course, the main point for amateurs. For the sake of more perfect illustration it will be presumed that the plants are in a temperature of 65° (which is re-garded as a stove heat), and have eventually to be set out in the open ground. The first stage is to remove them to a cool greenhouse, where the normal temperature would be about 50° ; but even here it is advised that they be set in a part where the cold air through the ventilators will not play directly on to them. After a few days they may be put in a more airy part. The next removal will be to a cold greenhouse or a cold frame, but for a couple of days