MAPLE SIRUP PRODUCERS MANUAL 



wood forests. In the ideal sugar grove, most of 

 the other trees have been cut out and the 

 maples have been thinned sufficiently to allow 

 the trees to develop a good crown growth (,63). 

 Thinning should be done according to a care- 

 fully planned program, with the assistance of 

 the State extension forester and the State for- 

 ester for the area. If the stand is made up 

 entirely of maples, approximately the same vol- 

 ume of sap is produced per acre regardless of 

 the size of the trees (^6). As the number of trees 

 per acre decreases below 160 trees 10 inches in 

 diameter at breast height (d.b.h.) or 40 trees 25 

 inches d.b.h., the size of the crovvTis and the 

 yield per tree may increase but the cost of 

 collecting sap also increases because the dis- 

 tance between trees requires longer sap mains 

 when tubing is used, and sap collected by hand 

 must be carried farther. 



Figures 1 and 2 show a maple grove with the 

 large full crowns that are so important to the 

 production of large amounts of sweet sap. 



For maximum returns, the grove should con- 

 tain at least SOOtapholes, that is, a minimum of 

 500 trees 10 inches d.b.h. Groves with fewer 



than 10 maple trees per acre are not profitable; 

 groves with 30 to 40 trees 25 inches d.b.h. are 

 ideal (<54). 



Maples grown in the open — for example, 

 along the roadside (fig. 3) — are excellent sap 

 producers (6Jf, 65, 67) not only because they 

 have large crowns but also because they have a 

 large leaf area, which is necessary for both 

 starch and sugar production. Because of their 

 shorter boles, roadside trees do not make as 

 good saw logs as do trees that grow under 

 crowded conditions. Studies have been con- 

 ducted on the effect of fertilization {^6). 



Trees in a crowded stand have smaller 

 crowns and therefore are not good sap produc- 

 ers (figs. 4 and 5) because of their reduced leaf 

 area. 



The ideal sugar grove (figs. 6 and 7) requires 

 not only a planned spacing of trees but also a 

 good understory to protect the ground, keep it 

 moist, and permit growth of seedling maples to 

 replace mature trees that should be cut down 

 (fig. 8). Often these mature trees can be sold for 

 lumber. However, there is no such thing as a 

 dual-purpose maple tree — one that serves 



PN-469S 



Figure 1. — Grove of maple trees v/ith large crowns.which 

 are needed for large yields of sweet sap. 



PN-4699 



Figure 2. — Same grove shown in figure 1 after defoliation, 

 showing the branch structure of trees with large crowns. 



