RAISING PLANTS 171 



or six weeks. Some attention will have to be given to the 

 matter of ventilating the hot-bed by raising the sash a little. 



A cold-frame is made almost exactly like a hot-bed, except 

 that no manure for heating is used. The only heat supplied is 

 that from the sun through the glass. A cold-frame is used 

 usually for hardening plants that have been grown in a hot-bed. 

 If cabbage and tomato plants that have been grown in a hot- 

 bed were to be planted out in the open garden early in the 

 spring they would probably die because of the great change 

 from warm to cold, but if they are transplanted to the cold- 

 frame for a few days they get hardened, so that they will 

 stand a good deal of cold without injury. Sometimes cold- 

 frames are used for growing lettuce and other plants that do 

 not need much warmth. 



The greenhouse is really only a collection of cold-frames 

 and hot-beds. The heat is furnished from a furnace and 

 a special glass building is constructed to let in the sunlight. 

 Only gardeners who supply large markets and who grow 

 vegetables for winter market can afford the expense of a 

 greenhouse. 



Transplanting. — The young plants of cabbages, tomatoes, 

 and many other vegetables are usually started in the green- 

 house or hot-bed, and when the weather is warm enough they 

 are set out in the garden where they are to grow. This- reset- 

 ting is called transplanting. If possible, transplanting should 

 be done on cloudy days or during damp weather. Where 

 only a few plants are to be moved, they can usually be set out 

 in the evening or before a shower. Plants do better if reset in 

 freshly prepared ground. The soil should be pressed down 

 closely around the roots, and the surface left loose to act as a 

 mulch. Some gardeners pour a tinful of water around each 



