THE INFLUENCE OF CERTAIN ENVIRONMENTAL AND 
CULTURAL CONDITIONS ON FRUIT-BUD FORMATION 
OF PEAR AND APRICOT * 
By C. B. Wiggans a 
Department of Horticulture, University of Arkansas 
INTRODUCTION 
The pear and apricot fruits are formed from flower buds differen¬ 
tiated during the summer previous to blossoming. It is generally 
assumed that fruit-bud formation can be influenced only by opera¬ 
tions performed before the time of differentiation. If this is true, 
the orchardist is not only interested in the approximate time of 
differentiation, but also in the influence which certain cultural opera¬ 
tions, such as pruning and irrigation, may have on the time and 
subsequent development of fruit buds. To add to the present 
knowledge of flower-bud formation, and to obtain information which 
might be of immediate practical value to the fruit industry of Cali¬ 
fornia, an attempt has been made to answer the following question: 
What influence do (1) different degrees of severity of dormant 
pruning, (2) irrigation, and (3) climatic conditions in the coastal 
valleys, interior valleys, and foothills have upon the time of differ¬ 
entiation and the rate of development of the fruit buds of the pear 
and apricot? 
As far as the writer knows, the only exact data which had been 
collected with regard to fruit-bud formation in California previous to 
the present investigation were those that dealt with average interior- 
valley conditions, no attempt having been made to determine the 
influence that such cultural practices as pruning and irrigation might 
have upon the time of differentiation and subsequent development 
of fruit buds. Likewise, data collected in the Eastern and North¬ 
western States possibly do not apply directly to California condi¬ 
tions, and furthermore, these other investigations have devoted 
little attention to the special problems involved here, since irriga¬ 
tion with them is not a common practice and neither does there 
exist such a diversity of pruning methods as in California. 
Pruning, commonly recognized as a necessary orchard operation, is 
one of the most expensive and time-consuming practices of the Cali¬ 
fornia orchardist. In this State there are practically as many prun¬ 
ing methods as fruit-growing sections. Until recently the common 
practice in California has been to severely head back at the dormant 
pruning. A radically different method is rapidly gaining favor. 
This system consists essentially of thinning-out only and is popularly 
known as “long” pruning as opposed to the method of heavy heading- 
back or “short” pruning. 
1 Received for publication Nov. 28, 1924; issued January, 1925. The work was carried on under the 
auspices of the California Agricultural Experiment Station. 
2 The writer wishes to express his appreciation to the following: Prof. W. P. Tufts for counsel and sug¬ 
gestions in planning and carrying forward this investigation; Dr. W. W. Robbins and Dr. W. L. Howard 
for suggestions and criticisms on the preparation of the manuscript; Miss Edna Russ for her assistance in 
the preparation of the photographs; and B. J. Jones and Henry P. Everett “for collecting part of the 
material. 
Journal of Agricultural Research, 
Washington, D. C. 
( 865 ) 
Vol. XXXI, No. 9 
Nov. 1, 1925 
Key No. Calif.-42 
