BETTER FRUIT 



KDITOR: W. H. WALTON 



STATE ASSOCIATE EDITORS 



OREGON— C. I. Lewis. Horticulturist. 



WASHINGTON — Dr. A. L. Melander. Entomologist ; 

 O. M. Morris. Horticulturist. Pullman. 



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

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

 Fort Collins. 



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



MONTANA— H Thornber. Victor. 



CALIFORNIA — C. W. Woodworth. Entomologist. Berke- 

 ley; W. H. Volck. Entomologist. Watsonrille; Leon D. 

 Batchelor, Horticulturist. Riverside. 



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



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Entered as second-class matter April 22, 1918, 



at the Postofflce at Portland, Oregon, under 



the Act of Congress of March 3, 1879. 



Volume XV 



Portland, Oregon, January, 1921 



Number 7 



Stock Influence on Scion In Regard to Top Grafting 



By A. E. Murneek, Assistant Professor of Horticultural Research, Oregon Experiment Station 



of producing dwarfed trees by growing 

 standard varieties on dwarf or dwarf- 

 ing stocks. The apple on Doucin or 

 Paradise stocks, the pear on the quince, 

 the cherry on Mahaleb are but a few 

 familiar examples. 



1. The diminished size in most cases 

 of dwarfing is due to a lack of supply 

 of raw material to the scions, or a par- 

 tial starvation. The cause of this may 

 be attributed either to the particular 

 character of the stock or, in some in- 

 stances, to the imperfections and con- 

 striction of conducting vessels at the 

 point of the graft union. In many in- 

 stances, however, the scion partakes of 

 the character of the stock to an extent 

 which cannot be ascribed to the dimin- 

 ishing of food supply alone, but rather 

 to some more specific and more pro- 

 found effect brought about by a selec- 

 tive influence of the protoplasm. 



2. As the stock has a tendency to im- 

 part its characteristics to the scion and 

 as the commonly used stocks for top 

 working are more vigorous than the 

 scion, we can expect thus an increase 

 in vigor of the top grafted tree. That 

 many varieties of apples have been 

 changed in vigor because of top graft- 

 ing we have not only individual but also 

 cumulative evidence, as will be seen 

 below. In most instances vigor has 

 been increased by top working, espe- 

 cially with such weak growing varie- 

 ties like Grimes, Winesap and others. 

 In an investigation of the adaptability 

 of various stocks for the American 

 grape, Hedrick reports that all top 

 grafted vines are more vigorous than 

 when grown on their own roots, as- 

 cribing this to the existence of a high 

 degree of congeniality between the 

 stocks and varieties under test. 



The general cause of increase in vigor 

 of top grafted trees may be due either 

 to an increased supply of sap or raw 

 material by the more active or faster 

 growing stock, or due to some specific 

 influence, which is of mutual benefit to 

 bolh the stock and scion, and is often 

 covered in a loose and general way by 

 (he term "congenial." That many var- 

 ieties-are made more vigorous when 

 grafted on a particular stock (not nec- 

 essarily of more vigorous growth) has 

 long been an observed fact among prac- 

 lical horticulturists, though the reason 

 of Ibis effect is not known. Most ap- 



THAT the two consorting parts of 

 the graft, though remaining dis- 

 linctly individual in their main 

 characteristics, are reciprocally influ- 

 enced by each other, has long been the 

 subject of observation and study. 



It is well known to most nurserymen 

 that the scion or top of a grafted tree 

 has a marked effect upon the stock or 

 root system of the plant. This impres- 

 sion may be so profound and character- 

 istic that varieties may be recognized 

 by the root system formed, though the 

 root be originally but a mongrel seed- 

 ling. Unright growing varieties of 

 apples of the Russian type, for instance, 

 will form a correspondingly deep-grow- 

 ing root system, while those of the 

 spreading Winesap type will be flat and 

 shallow. This can be extended even to 

 particular varieties. The Red Astra- 

 chan, Oldenburg, Fameuse, for example, 

 form each a characteristic root system 

 of their own. In this connection, Shaw 

 believes that "the size or stoutness of 

 the main branches is positively corre- 

 lated with the size of the main roots 

 and angle of the branch with the angle 

 of the main roots and the axis of the 

 tree. In many individual cases this 

 correlation is obscure, yet careful ob- 

 servations with large numbers of trees 

 will reveal it." 



But it is not only the form of the root 

 that is changed by the stock. The phys- 

 iological modification brought about in 

 the root may be effective enough to 

 make it markedly different in hardiness 

 and resistant to many external vicissi- 

 tudes. To what degree of economic 

 importance are these modifications can, 

 however, only be conjectured. 



The reverse of this, the influence of 

 stock on scion, has been the subject of 

 much more recorded opinions and ob- 

 servations than that of the scion on the 

 stock. 



English horticultural literature, espe- 

 cially the pages of the "Gardener's 

 Chronicle," abound with plentiful and 

 rich information on this topic. Though 

 very scattered and more or less of a 

 subjective nature, there is much mate- 

 rial on this question recorded in the 

 transactions of various state horticul- 

 tural societies. 



From the point of view of the fruit 

 grower, the subject falls under two 

 topics: First, the influence of the stock 



on the scion proper, and, second, the 

 indirect influence on the fruit. 



Influence of Stock on the Tree. 

 The ways in which the scion may be 

 modified by the stock may be in re- 

 spect to — 



1. Form and size of the plant. 



2. Vigor of growth. 



3. Health. 



4. Hardiness. 



5. Productivity; precocity. 



6. Time of blossoming and maturing 

 of fruit. 



Some of these may not be directly 

 traceable to the stock, but rather the 

 secondary results of one or more of the 

 above effects. Thus many of the modi- 

 fications stated above may be due to 

 increased vigor of the plant. Again, 

 productivity is often directly depend- 

 ent upon health and so is longevity. 

 These in turn may be closely connected 

 with hardiness. 



That the stock has a marked and 

 characteristic influence on the scion in 

 respect to form and size of the tree is 

 well illustrated in the common practice 



Fig. 1. Cornice pears. Scions overgrowing 

 stock. Such differences in growth must have 

 some effect upon the performance of the tree. 



