INFLUENCE OF STOCK ON CION 



In Grafted Trees, One Parent Usually Modified, Sometimes Both — Explanation 

 of the Changes — Remarkable Almond Grafts in California. 



B. S. Brown 

 Professor of Pomolofiy and Plant Breedinsi, University of Maine, Orono, Me. 



MUCH has been said in recent 

 x'ears regarding the effects of 

 graftage upon the co-joined 

 jjarents. That there is a very 

 decided difference in certain fruits 

 when grafted upon different stocks no 

 one will deny. But to what extent these 

 influences represent fixed or dependable 

 characters is still an open question. 



The best recognized example of 

 reciprocal influence is the dwarfing of 

 certain standard fruits when grafted 

 upon smaller stature plants. Thus 

 pears are put upon quince or apples 

 upon doucin or paradise stock^ for this 

 purpose. While slow-growing stocks 

 tend to reduce the stature of plants 

 grafted upon them, the converse of this 

 is also true, that rajjid-growing stock 

 will stimulate the growth of naturally 

 dwarf plants. While quince stock will 

 reduce the size of a pear tree, a pear 

 stock will increase the stature of a 

 quince that is worked upon it. This is 

 not only true in the above relation but 

 also where conditions are reversed. 

 That is, pears grafted on quince stock 

 will stimulate greater root growth to the 

 quince. Another o^t-citcd example of 

 this same condition is the influence of 

 standard apples when grafted on stock 

 of the Siberian Crab. Such a union 

 alwayr stimulates the root system of the 

 stock to a larger siz.. than it would 

 grow naturally. 



Because of the commercial importance 

 (){ the subject, growers of all kinds of 

 fruit are now attempting to find out 



definitely the reciprocal influence of 

 various kinds on each other. One of 

 the interesting experiments is that 

 made by grafting tomato on belladonna, 

 when analysis showed that the tomatoes 

 borne contained an alkaloid allied 

 chemically and phj siologically to a tro- 

 pin, whereas tomatoes do not normally 

 coniain any .such substance. - 



The California agricultutal experi- 

 ment station has been eonducling a 

 series of < xperiments to determine the 

 exact results in various grafts on citrous 

 fruits. One of the interesting results, 

 which may serve as a specimen of 

 many, is that when lemons are budded 

 on the hardy, savage, Japanese, three- 

 leaved species {Citrus trifoliata), they 

 are dwarfed, and the diameter of the 

 trifoliate stock, below the bud union, 

 is nearly always increased.^ 



While investigating the almond in- 

 dustry in Central California recently, I 

 discovered a peculiar case of reciprocal 

 influence of stock and cion, to which it 

 may be of interest to call attention. 

 An orchard of 10 acres had been set 

 to peaches and then a year later toj)- 

 workcd to almonds, the union being 

 made just above the ground. The 

 orchard had been in existence for 42 

 years and contained many trees as 

 sound as they were at the age of five. 



Many of these trees were 50 feet 

 high and ranged from two to three feet 

 in diameter. Figures two and three are 

 individual trees in this orchard, showing 

 the peculiar enlargement at the i)oint 



' Doucin and Paradise are types of wild apj)!'.', probably of central Asian oriKin, which are 

 widely grown for stock on which to hud cullivaled varieties of apjile. In the jiast they have 

 betn eonsid'-red distinct species but at present are held rather to be trade names, each one 

 embracing 10 i>T a dozen varieties of the ordinary apple. Doucin stock is used when "semi-dwarf" 

 trees are wanted; while the use of Parachse stock results in a still greater reduction of size. 



*See Gardeners' Chronicle, London, May 16, 1914. 

 F 'This was pointed out 10 years ago by H. H. Hume (Citrus Fruits and their Culture, 1904) 

 and is true of all species and varieties that have been tested (jn trifoliata stock. 



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