Variations in citrus seedlings and their relation to rootstock selection

Abstract

does not appear. First page follows. Although the question of securing the best rootstocks to use in citrus propagation has for many years attracted the attention of growers, experimentation on the subject has been very limited. The earliest general publication on citrus stocks in America, that of (Van Deman (1891)), is a summary of the observations and studies made on groves in Florida and is not based on comparative experiments. (Mills (1902)) has described the results of certain experiments conducted by the California Experiment Station at Pomona, California; and (Bonns and Mertz (1916)), the results of a series of comparative experiments made at the Citrus Experiment Station at Riverside. A carefully planned and executed experiment was also carried out for a limited time by (Taber (1904)) at Glen St. Mary, Florida, with certain varieties propagated on Trifoliate orange, sour orange, and sweet orange. The experiment was designed primarily to determine the comparative value of the cold-resistant Trifoliate orange as a stock. As a result of these studies and experiments and of the cumulative understanding of growers derived from long experience, certain stocks have come to be commonly used, and success in general has been achieved with them. It is well recognized, however, that the problems connected with rootstocks are poorly understood, and there is little evidence to justify a conclusion that the species and varieties now used as stocks are the best available. A fair appreciation of the value of sour orange, sweet orange, lemon, grapefruit, and certain other species as stocks has been acquired, but until recently no attention has been directed to variations within these species and the influence of such variations on the fruit or scion variety. Until recently this was also the case in the propagation of all other commercial fruits, such as the apple and pear. The experiments herein reported, which were started in 1914 (Webber, 1919) and (1920), resulted in directing attention to the great variability among seedlings of the same species or stock type, and to the probable influence of such variation on the uniformity of the orchard trees produced. The present paper will outline the results obtained with these experiments up to the present time, and will discuss briefly the influence that the findings may have in improving nursery methods in the future.