HORTICULTURE A GREAT GREEN CARPET 427 



orchardist must select varieties to interplant for effective cross-pollination 

 and fertilization. And he would not use as pollenizers such triploid varieties 

 as the Gravenstein and Baldwin apples, nor the J. H. Hale peach, all of which 

 have defective pollen. This has been the product of research. 



In commercial practice, the bee may be used as the agent for pollinating 

 with some regard to temperature, bee flight, and number of bees required 

 for a given area. Traps have been devised so that pollen is scraped from the 

 creatures as they enter the hive loaded with pollen. In turn this pollen has 

 been placed in trays at the hive egress, so that bees emerge coated with proper 

 pollen ready for business. Hand pollination has been found practical in 

 some areas, and shot-gun shells loaded with pollen have been fired with some 

 success at trees in the unfortunate modern tempo of treating everybody and 

 everything as an adversary! 



Some plants, as the tomato and cucumber, will respond to applications of 

 certain chemicals, such as />arc-chlorophenoxyacetic acid for fruit setting, 

 and will produce seedless fruits without pollination and fertilization. Further, 

 it has been found that the tomato does not set fruit when night temperatures 

 are below 59°F. Under such conditions, hand spraying with plant-regulating 

 chemicals and raising the night temperature by artifical covering have both 

 proved effective. As an additional practical sidelight, the knowledge that 

 tomatoes do not set fruit in early spring until night temperatures are above 

 59°F. has made it possible to forecast several weeks in advance when the 

 main crop of tomato fruits will reach the local market. 



Blossom thinning and fruit development. In recent years, securing a 

 set of fruit has become less of a problem generally in orchard circles than 

 thinning off excess fruits. Here it has been found that early thinning is 

 most effective, beginning with blossom thinning. It is interesting to note in 

 this connection that as long ago as 1835, Robert Manning of Salem, Massa- 

 chusetts, one of America's early pomologists, found that by removing all the 

 blossoms from some biennially bearing apple trees and not from others, he 

 caused some trees to fruit one year and others the next, thus ensuring fruit 

 each year. However, thinning of fruit by hand is now largely a thing of 

 the past. In its place are chemical thinning and pole thinning of various types, 

 in which blossoms and young fruits are literally beaten or brushed crudely 

 from the trees. 



Thinning of apples by means of blossom-thinning sprays has become stand- 

 ard practice in large areas, and there is some success with peaches from appli- 

 cations several weeks after bloom. Dinitrocresols have been used in some 

 regions, but growth regulators, such as naphthaleneacetic acid and naphtha- 

 leneacetamide, have been found more effective in others. It has been learned 

 that such sprays tend to "knock off" the weak blossoms and leave the strong, 

 so that the quality of the remaining fruit is improved both by reduction of 

 competition and by "the survival of the fittest." The concentration of the 



