29 



Yield. The principal returns from the hard maple will be 

 that of sap for syrup or sugar, and the planting should be 

 made with the idea of maintaining a sufficient stand to shade 

 off lower limbs. Trees with full crowns and an abundance of 

 foliage yield the greatest amount of sap, and the planting 

 should be made with this object in view. One thousand trees 

 per acre are entirely too many to allow to grow to maturity. 

 When they begin crowding each other fully half of the trees 

 may be tapped and bled to death during a period of three or 



FIG. 179. A grove of sugar maple trees growing in Linn county, Kansas. 



four years. These should then be cut out to make room for 

 the remaining trees, which should grow until they reach a 

 diameter of from 12 to 15 inches before tapping is begun. 

 From this time on, by careful management, they may be bled 

 annually without serious loss or injury to the trees. 



No very definite data can be given on the yields from the 

 maple industry, as so many factors enter into consideration. 

 From 5 to 40 gallons of sap are obtained from a tree during 

 a season ; an average is somewhere between 10 and 20 gallons. 

 Normal sap of an average year contains about 2 per cent of 

 sugar, although it may vary from .5 per cent to as high as 

 7 or even 10 per cent. The sugar content varies greatly with 



