of New York 23 



correct working knowledge of trees will go far to guarantee 

 a sound program of forest conservation, which is one of the 

 most vital problems confronting the people of our state. 



WHEN TREES GROW 



MOST PEOPLE believe that trees grow from early spring 

 when the leaves begin to come out until the first frost 

 when they start to show their autumn color. That this wide- 

 spread belief is not correct is now known. For instance in 

 the latitude of southern Pennsylvania our native forest trees 

 make 90 per cent of their height growth in 40 days of spring 

 and early summer. 



Not all trees begin to grow at the same time. Some begin 

 early in spring, while others delay starting their growth 

 until late April or early May. The Wild Black Cherry 

 starts about the first of April, while the Tulip Tree or Yellow 

 Poplar does not begin until late in April, and the Norway 

 Spruce waits until early in May. The fact that the different 

 trees start their growth at different times may not seem 

 strange, but where is the person who is not amazed to learn 

 that the Sweet Buckeye has its whole height growth for the 

 season completed in some regions by the tenth of May. For 

 ten years the author has watched different specimens of this 

 tree in Pennsylvania, and with no single exception all the 

 height growth for the year was finished by May 10. This 

 means that the height growth took place in 35 days in spring- 

 time. 



An even greater revelation of this growth study was the 

 fact that growth takes place by leaps and bounds. Periods 

 of rest often occur between periods of growth. These rest 

 periods may be long or they may be short. In this respect 

 trees are not different from boys and girls who are willing 

 to have long rest periods scattered freely among their work- 

 ing hours. 



Several years ago, the author tagged a chestnut oak tree 

 and measured its growth carefully. It began growing on 

 April 17, and grew regularly until May 23. Then it began 

 a rest period of 32 days. On June 24 it started to grow 

 again and continued until July 13. If you figure out this 

 tree's height growth you will find that at the beginning of 

 the season it grew for 36 days, then rested for 32 days, and 

 thereafter grew again for 20 days. During the first growth 

 period it grew 10 inches — an average of about one-third of 

 an inch per day, and during the second period 13^ inches — 

 an average of more than three-fifths of an inch per day. 



