68 PLANT GROWTH 



spring, when they are planted, but kept cold enough to 

 retard bud growth until the roots are well developed. Some- 

 times they are buried in the garden deep enough to be below 

 the frost line. Green wood cuttings may be made during the 

 summer, but since transpiration is Hkely to be excessive, part 

 of the leaf surface should be removed and the cuttings should 

 be shaded and should be sprinkled gently often enough to 

 keep the surface moist. In greenhouse propagation cuttings 

 are shaded and sprinkled once to several times a day. 



Cuttings must have a good set of roots to produce good 

 plants. The same four closely related conditions must be 

 considered for cuttings as was described for growing seed- 

 lings, namely: plenty of stored food, adequate oxygen, mois- 

 ture, and temperature. It has been found that cuttings 

 made from tissue with a good supply of stored food will use 

 it in better rooting and in growing a stronger plant. They 

 need extra oxygen to oxidize the food and so are usually set 

 in sand. This can be kept well moistened but still remain 

 well aerated. Bottom heat is beneficial to hasten root 

 growth when started on a greenhouse bench. They should 

 be restricted from excessive transpiration, but some air circu- 

 lation may be necessary to avoid the growth of damping off 

 fungus. Most cuttings root better if they are made at right 

 angles instead of long tapering cuts. 



Root cuttings may be used from plants that sucker natu- 

 rally from the root. Raspberry and blackberry root cuttings 

 are frequently made about two or three inches long from 

 roots about as thick as a pencil. The cuttings may be made 

 by taking a piece of root with a small sucker. Root cuttings 

 should be planted very shallow to allow the bud to reach the 

 surface quickly and begin to make food. 



Grafting is the placing of a cutting of last year's growth 

 called the scion into another plant called the stock in such 

 a manner that like tissue will grow together and become a 

 single plant. There are several kinds of grafting, but they 



