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AMERICAN HOMES AND GARDENS 



November, 1910 



Glass Espalier Walls 



By Jacques Boyer 



N THE cultivation of fruits on the espalier 

 system, the trees and vines are planted 

 along a wall of stone or brick, to which 

 all their branches are carefully attached, 

 so as to spread them out into a plane 

 surface, and allow free access of light and 

 air to every part. Ordinarily, the direc- 

 tion of the wall is determined by local circumstances, and 

 the varieties of pears, cherries, peaches, apricots, apples, 

 and other fruits which are planted along the wall, are 

 selected with reference to this direction. Until very re- 

 cently, if the wall was built in an east and west direction, 

 so as to expose one face to the south, the other face was 

 ialmost entirely wasted. In order to remedy this state of 

 affairs, several fruit growers have conceived the idea of 

 employing trans- 

 parent espalier 



walls, through ' 



which the light 

 of the sun can pen- 

 etrate to the trees 

 planted on the 

 north side of the 

 wall. Count Hor- 

 ace de Choiseul, in 

 particular, has con- 

 ducted a series 

 of very interest- 

 ing experiments 

 of this sort on 

 his estate at Viry- 

 Chatillon, in the 

 Department 

 of Seine-et-Oise, 

 and has obtained 

 some very prom- 

 ising results. He 

 built a glass wall 

 GYz feet high and 

 about 60 feet 

 long, extending 

 in an east and 

 west direction, 

 and planted fif- 

 teen pear trees 

 of the variety 



"Winter Doyen" on each side, north and south. The bear- 

 ing surface of the wall amounted to about 26 square yards 

 on each side. The south side yielded 134 pears of a total 

 weight of 91 pounds, and the north side bore 119 pears 

 weighing 77 pounds, making in all 243 pears with an aggre- 

 gate weight of 168 pounds. All of the pears were of par- 

 ticularly fine appearance, without blemishes of any kind, and 

 it is a remarkable fact that the fruit which was gathered 

 from the north face of the wall was even smoother of skin 

 than that which was produced on the southern side. Each 

 square yard of the glass wall produced nine or ten pears of 

 an average weight of about 1 1 ounces. 



Another experiment with glass espalier walls has been 

 made by MM. Croux & Sons in their nursery at Val 

 d'Aulnay in the Department of the Seine. The wall which 

 they constructed also lies east and west, and consequently 



presents northern and southern exposures. As the accom- 

 panying photographs show, the wall is surmounted by a 

 glazed roof projecting on each side. Along each face of 

 the wall were planted Calville apples. Winter Doyen, Passe- 

 Crassane, and Directrer Alphand pears, together with peach 

 trees and grape vines, care being taken to place the same 

 varieties on each side, in order to make the comparison 

 easy and accurate. 



In 1907 these trees and vines produced their first crop, 

 in which no difference between the fruit produced from the 

 north and south sides of the wall could be detected. The 

 same result was shown by the crops of 1908 and 1909. 



There is, indeed, little difference in temperature between 

 the north and south faces, as the former is heated by the 

 solar rays which traverse the glass, and the latter is cooler 



than the south 

 side of a masonry 

 wall, for the 

 very reason that 

 some of the inci- 

 dent solar radia- 

 tion is trans- 

 mitted through 

 the glass and 

 consequently less 

 is reflected and 

 absorbed. This 

 difference in ab- 

 sorbing power, 

 however, makes 

 the glass wall in- 

 ferior to the 

 masonry wall in 

 the matter of 

 warming the 

 plants and pro- 

 t e c t I n g them 

 from frost at 

 night. A masonry 

 absorbs a 

 deal of 

 during the 

 and gives it 



A glass espalier wall 



wall 

 great 

 heat 

 day 



out at night, but 

 this effect is com- 

 paratively small 

 in the case of a wall of glass. 



In the matter of cost, there is little difference between 

 the glass and the masonry walls. The cathedral glass em- 

 ployed by MM. Croux costs about $6 or $7 per linear 

 yard of wall eight feet high, including the cost of the 

 glazed roof projecting over both sides. A masonry wall of 

 the same height would cost $4 or $5 a yard, and the addi- 

 tion of the glazed roof, which of course is equally necessary 

 in this case, would raise the total cost to $6 or $7 per linear 

 yard. More extensive and long-continued experiments 

 must be made, however, before it will be possible to pro- 

 nounce a positive opinion concerning the relative merits of 

 glass and masonry espalier walls,- but the work already 

 accomplished is sufficient to show that the practical French 

 gardener may continue to be counted on to furnish im- 

 provements in his field. 



