14 
BULLETIN 1477, U. S. DEPARTMENT OF AGSICULTUEE 
Table 1. — Maximum, minimum, and mean temperatures, May to September, 
inclusive, for cool and warm plum-producing districts in California 
[Data for cool and warm plum-producing sections, from the summaries of climatological data for the United 
States by sections for the different stations of the Weather Bureau, as follows: A, United States Depart- 
ment of Agriculture, Weather Bureau, summary of the climatological data for the united 
states, by sections. reprint of section 14.— central and southern california, p. 23, 1925. b, 
United States Department of Agriculture, Weather Bureau, summary of the climatological 
data for the united states, by sections. reprint of section 15.— northeastern california, p. 36, 
37, 1917.1 
Stations 
Temperatures ( 
°F.) 
May 
June 
July 
August 
Septem- 
ber 
Oakland ( A) _ 
Auburn (B). 
(Maximum 
< Minimum 
[Mean 
[Maximum 
69.0 
50.2 
58.1 
74 7 
50.1 
62.7 
78.5 
48.6 
642 
72.7 
52.7 
61.5 
85.1 
55.0 
70.8 
84.1 
51.7 
71.0 
73.0 
53.8 
61.8 
91.7 
61.1 
76.8 
93.5 
55.8 
75.5 
70.2 
543 
61.3 
91.8 
60.3 
75.9 
92.1 
55.6 
74 5 
70.6 
541 
61.2 
83.5 
545 
Vacaville(.B)_ 
(Mean 
(Maximum 
I Minimum 
[Mean 
71.0 
86.4 
52.5 
70.8 
The difference in temperature of these regions has decidedly less 
effect on the rigor of the varieties of the domestica group than of 
the Japanese, although the vigor in the fruiting twigs has been ob- 
served to be notably less with the varieties Grand Duke and Diamond 
than with most others in the cooler region or when compared with 
trees of the same varieties in the warmer places (pi. 3, B, and 20, B). 
^Washington and Sergeant illustrate domestica varieties which grow 
well in cool as well as warm sections (pi. 3, C, and 34, B). 
HABITS OF GROWTH AND PRODUCTION OF SOME PLUM VARIETIES 
GROWN IN THE PACIFIC STATES 
VARIETIES OF THE PRUNUS TRIFLORA GROUP AND ITS DERIVATIVES OR HYBRIDS 
Tree very vigorous, erect, branches very freely, and produces and retains 
fruit spurs and twigs in all parts (pi. 4, A). 
The shoots which grow freely from cut-back tops and along fruiting branches 
and trunks of open trees make a rapid, slender, upright growth ; and those 
on the outside of the tree or in open trees branch freely their first season. 
The new branches are slender, make an upright growth, and are often numer- 
ous, thus producing a compact top and dense shade lower in the tree. Slender 
twigs and longer shoots appear at the terminals of spurs and twigs through- 
out heavily pruned trees (pi. 4, B). When the tree is lightly pruned and 
other conditions are unfavorable for wood growth, spurs and twigs make 
little or no new wood, lose vigor, and produce small fruit. In unirrigated 
orchards the wood growth is decidedly less than in irrigated ones, and fewer 
large shoots and long fruiting twigs are produced, except in the tree top. 
Instead of the long slender branches and twigs which are found throughout 
the body of the tree in the irrigated orchard there are short twigs and spurs. 
Spurs on this variety form in greater numbers than on almost any other, 
appearing at almost all nodes along the 1-year-old wood. In this the Beauty 
differs from the many varieties which bear heavily on 1-year-old wood but 
fail to produce spurs there. The spurs are slender, easily broken, branch 
freely in open places in the tree, are long lived and productive, and those 
bearing fruit are more inclined than those of most other varieties to produce 
a good crop of leaves. In shaded places and on trees which are growing 
