RELATION OF EARLY MATURITY TO HARDINESS IN TREES. 22 5 



RELATION OF EARLY MATURITY TO HARDINESS IN 



TREES. 



PROF. R. A. EMERSON, UNIVERSITY OF NEBRASKA, LINCOLN, NEB. 



That there is a close relation between early maturing and hardi- 

 ness is well known. Every one knows that a tree might be killed 

 by a light freeze in June, though it had withstood the extreme cold 

 of the preceding winter. I do not want it understood that I consider 

 lack of maturity the only cause of winter injury. Some plants are 

 constitutionally hardier than others of the same degree of maturity. 

 For instance, beans and peas behave very differently toward frost, 

 the one being killed and the other uninjured, though both may be 

 immature and growing rapidly. 



Before calling your attention to some of the ways in which a 

 knowledge of the relations of early maturity to hardiness can be 

 made use of by the practical horticulturist, I desire to give you a few 

 illustrations of this relation. 



In the group of plants to which plums and peaches belong, some 

 species are hardier than others, and some ripen their wood earlier 

 than others, but is there any connection between these two facts? 

 The peach is an extremely late grower and is not hardy. The 

 Chickasaw plums mature their wood fairly early and are fairly 

 hardy ; the wild plums of the northwest stop growing early and 

 spend the whole autumn in maturing their tissues, and you all know 

 that the native plums are ironclad in hardiness. 



The same thing holds true for varieties of apples. The Whitney 

 crab in Nebraska nurseries stops making length growth in July, and 

 all the warm weather or rains of autumn cannot induce it to make 

 a second growth. The Oldenburg stops growing almost as soon, but 

 will sometimes make a small second growth. I need not remind 

 you of the hardiness of the Whitney crab, nor tell you that the 

 Oldenburg is only slightly less hardy. The Wealthy and North- 

 western Greenings are somewhat slower in maturing their summer's 

 growth, and, while hardy, they will, nevertheless, not stand the try- 

 ing conditions the Whitney or Oldenburg will endure. Ben Davis, 

 Winesap and many other varieties mature their wood fairly well 

 and with us in Nebraska are found hardy, yet they are injured some 

 winters. Grimes' Golden is still later in maturing, and one year old 

 nursery trees of Grimes' are often killed to the snow line, even in 

 southeastern Nebraska. 



All of you know that young seedlings or grafts are winter injured 

 much more frequently than older trees of the same sort, providing 

 the trees are not so old as to be feeble. It only remains to note that 



