WINTER INJURY 269 



Northern trees are constitutionally no hardier than southern but their 

 superior resistance to winter cold was due to their habit of ripening their 

 new growth perfectly in the fall." 



Macoun''^ introduces evidence to the same effect: "From the writer's 

 experience with over 3,000 species and varieties of trees and shrubs, 

 exclusive of cultivated fruits, from many countries and climates, which 

 are under his care and observation at the Central Experiment Farm, 

 Ottawa, we have drawn the following conclusions regarding the hardiness 

 of trees: A tree or shrub which will withstand a test winter at Ottawa 

 must be one which ripens its wood early. Trees or shrubs which are 

 native to places having a longer or much longer growing season than at 

 Ottawa grow larger than native species or those from a somewhat similiar 

 climate to the native species, and when a test winter comes their wood is 

 not sufficiently ripened, or winter-resistant, and they are more or less 

 injured or perish. . . . Another observation regarding tender trees has 

 been that after a season when the growth has been strong more injury is 

 likely to occur than in a season when the growth is short . . . the 

 season of all the hardiest varieties [of apples] is summer or autumn . . . 

 apples which mature early and are in condition for eating in summer and 

 autumn are grown on trees which ripen their wood early, and, on the other 

 hand, an apple which is not ready for use until winter is usually grown 

 on a tree which does not ripen its wood early." 



Attention may be called to the doubtful wisdom of fall planting in 

 northern regions of trees grown far to the south. These trees, to be 

 shipped in time for planting in the north, must be dug when they are 

 still quite immature. They are, if planted in the fall, exposed to cold 

 winter temperatures and are thus doubly at a disadvantage. It is true, 

 the digging may in itself induce a degree of maturit}^ through drying out, 

 but hardly as much as would be attained by trees grown farther north. 

 The wisdom of delaying digging as long as possible is obvious. 



Tender Plants may he More Resistant than Hardier Plants. — A tempera- 

 ture of 15°F. at South Haven, Mich., on Oct. 10, 1906, uniformly 

 killed peach trees while pecans, in the same orchards, survived. ^^* Here 

 is undeniable evidence of a tender species being more hardy at that time 

 because of maturity than a species that is far more hardy in its mature 

 condition. Similarly, records show that apple trees planted 2 and 

 3 years in Wyoming were killed by a temperature of 12°F. in Septem- 

 ber, when they were still in full leaf ,^^ though there are numerous instances 

 of trees surviving approximately equal temperatures without material 

 injury when they were partly leaved out in the spring. 



The Effect of Slimmer Conditions Favorable for Late Growth. — During 

 the winter of 1903-1904 in Ohio, though the chief damage was to trees of 

 low vitality, vigorous trees succumbed in numerous cases. These were 

 almost invariably in "low, moist, rich black soil favoring extreme growth 



