﻿14 BULLETIN 13, U. S. DEPARTMENT OF AGRICULTURE. 



REPRODUCTION. 



Where it is planned to raise successive crops of trees, a comparative 

 study of the methods of reproduction is important. The best and 

 most economical means of reproduction are the natural ones afforded 

 by the stand itself, provided these can be relied upon. Artificial 

 methods are expensive, and require considerable technical skill in 

 carrying them out. On the other hand, since they do not require the 

 presence of trees to seed the area, a free choice of seasons and sites is 

 possible. With plantations the element of uncertainty which sur- 

 rounds natural reproduction is avoided. 



The abundance and thrift of the second growth white pine on 

 pastures and abandoned farms in the Northeast show that under 

 proper conditions white pine can reproduce itself excellently by 

 natural means. 



SEED PRODUCTION. 



The production of seed, like that of wood, depends upon the amount 

 of food which the leaves manufacture. With other conditions equal, 

 the more light a tree receives the earlier and more abundantly will it 

 bear. Thus full-crowned, open-grown trees will begin to bear earlier 

 and will produce more seed than small-crowned forest trees of the same 

 age and on the same kind of soil. Seed production is also earlier and 

 more abundant on good soils than on poor. With plenty of light, 

 white-pine saplings begin to bear cones when less than 20 years old. 

 As a rule, however, seed are not produced hi abundance until the 

 trees are from 35 to 70 years old, depending upon the amount of light 

 received. As the trees increase in age they bear more prolifically, 

 and the proportion of fertile seeds increases. With the decline in 

 vigor which attends old age there is probably a corresponding decline 

 in the amount and quality of seed produced, but white pine continues 

 to bear fertile seed in abundance for at least 200, and probably 300, 

 years. 



White pine cones require two years to mature. They begin to 

 form hi June, and by the fall of the first year reach a length of 1 or 2 

 inches. Thus it is possible to tell a year in advance whether or not 

 there will be a heavy seed crop. The cones reach their full length — 

 5 to 11 inches — early in the summer of the second year, and open in the 

 fall, usually in September. A frost sufficiently severe to kill squash 

 vines will often cause mature cones to open. Each cone bears from 

 50 to 75 oval seeds — two on the upper face of each scale — about one- 

 fourth of an inch long, and equipped with thin, membranous wings. 

 A bushel of cones will yield from one-half pound to a pound of cleaned 

 seeds, which run from 26,000 to 30,000 to the pound. 



Heavy crops of seed are borne at intervals of from 3 to 7 years, with 

 occasional intervening years of lighter production. The same year 



