BETTER FRUIT 



EDITOR: W. H. WALTON 



STATE ASSOCIATE EDITORS 



Lewis. Horticulturist. 



Meiander. Entomologist : 



OREGON— C. 



WASHINGTON - 

 O. M. Morris. Horticulturist. Pulln 



COLORADO— C. P. Gillette. Director and Entomologist; 

 E. B. House, Irrigation Expert, State Agricultural College. 

 Fort Collins. 



ARIZONA— F. J. Crider. Horticulturist, Tucson. 



MONTANA— H. Thornber, Victor. 



CALIFORNIA— C. W. Wood worth. Entomologist. Berke- 

 ley; W. H. Volck, Entomologist. Watsonville; Leon D. 

 Batchelor, Horticulturist. Riverside. 



INDIANA— H. S. Jackson. Pathologist. Lafayette. 



An Illustrated Magazine Devoted to the Interests 



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Entered as second-class matter April 22, 1918, 



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Volume XV 



Portland, Oregon, October, 1920 



Number 4 



The Propagation of Apple Trees on Their Own Roots 



By J. K. Shaw, of the Massachusetts Experiment Station 



THE methods of propagation of 

 tree fruits in common use among 

 nurserymen produce trees the 

 trunk and crown of which are of the 

 variety desired, while a part or the 

 whole of the root system is of seedling 

 origin. In many cases roots are thrown 

 out from the base of the scion that are, 

 of course, of the variety of the aerial 

 part of the tree, but it is doubtless true 

 that in most cases, especially with 

 budded trees, the seedling forms the 

 greater part, if not the whole, of the 

 root system. This means that in any 

 orchard of any one variety there is a 

 great deal of variation in the root sys- 

 tems. No two are of identical consti- 

 tution. This is due to the complexity 

 of the genetic constitution of our cul- 

 tivated varieties of apples. Seedlings 

 of a single variety, even if from self- 

 fertilized seed, show great variation 

 and many different combinations of 

 characters. 



It is reasonable to suppose that these 

 differing seedling roots should cause 

 more or less modification of the top, 

 and there is abundant evidence that 

 this is the case. The most common 

 example is found in dwarf trees. There 

 are many types of the common apple 

 that, when used as stocks, inhibit the 

 growth of the scion, and those that will 

 throw out roots from the stem readily 

 are used as dwarfing stocks. It is well 

 known that dwarf stocks influence also 

 the size, color, quality and season of 

 maturity of the fruit. It is therefore 

 reasonable to believe that many of the 

 individual differences among the trees 

 in an orchard may be due to the vary- 

 ing seedling root systems, and such in- 

 dividual differences, especially in pro- 

 ductiveness, are greater than is gener- 

 ally realized. If trees could be propa- 

 gated on their own roots, or on the 

 roots of a clonal variety known to be 

 well suited to the scion variety, much 

 might be gained in uniformity and 

 fruitfulness in the orchard. 



Another advantage in having trees 

 grafted on roots of known varieties 

 lies in the greater resistance to insects 

 and diseases of the roots that can be 

 secured in this way. This idea is in 

 practical use in Australia and South 

 Africa, where the method is used to 

 avoid serious trouble with the root 

 form of the wooly aphis. This insect 



was early imported from America, and 

 is there known as the American blight. 

 It was found that Northern Spy roots 

 were highly resistant to this insect, and 

 it is now the usual practice in those 

 countries to propagate all varieties on 

 roots of the Northern Spy, or some 

 other resistant variety. 



It has been the observation of the 

 writer that roots of different varieties 

 differ in their susceptibility to crown 

 gall, and it is reasonable to suppose that 

 the same may be true with other root 

 diseases. Root troubles are the cause 

 of failure of bearing trees more often 

 than is generally realized. Propagat- 

 ing varieties on known roots offers a 

 chance of overcoming, to a consider- 

 able degree, at least, many of these root 

 troubles. 



In the northern part of the apple belt, 

 especially in the prairie northwest, re- 

 sistance of the roots to extreme cold 

 becomes important, and it is considered 

 highly desirable to get varieties on their 

 own roots in order to avoid root killing 

 in winter, when the temperature of the 



soil falls to an extremely low point. 

 If trees of the varieties suited to these 

 conditions could be worked on roots 

 known to be of extreme hardiness, it 

 would contribute to the longevity and 

 consequent fruitfulness of the orchards. 



If we concede that trees growing on 

 roots of known varieties, either as own- 

 rooted trees or trees on roots of other 

 known varieties, may be more desir- 

 able for orchard purposes than trees 

 on miscellaneous unknown seedling 

 roots, there are suggested many prob- 

 lems for investigation. For example, 

 what varieties on their own roots are 

 resistant to the various insects and dis- 

 eases, and what ones possess extreme 

 hardiness to severe cold? What is the 

 effect of different varieties used as root 

 systems on the growth and fruitful- 

 ness of the scion variety? 



Before these problems can be solved 

 it is necessary to propagate trees on 

 their own roots. The general question 

 of the interrelation of stock and scion 

 is under investigation at this station, 

 and it is the purpose of this paper to 



Green wood apple cuttings, showing callus formation. From left to right: 

 Fall Pippin, Itcd Astrachan, Bough, Ben Davis, Wagene 



