22 BULLETIN" 1477, IT. S. DEPARTMENT OF AGRICULTURE 
loads of fruit cause the branch to bend with its load and often to become 
sunburned. Small fruit only may be expected where twigs cease to grow and 
spurs only are formed. Thinning out of branches or the improvement of 
growing conditions will be needed to cause an increase in wood growth (pi. 
16, B). 
Although wood growth is gradually checked by unfavorable conditions, the 
effect on trees of this variety is less prompt and less marked than with most 
varieties, and branches and twigs continue to lengthen under adverse conditions 
longer than with most other sorts. 
Most of the fruits are borne along the basal portion of 1-year-old twigs 
and on spurs. Fruit is also occasionally found near the base of rather large 
1-year-old shoots. When on 1-year-old wood it is usually found at leafless 
nodes of slender twigs, although sometimes at nodes of vigorous 1-year-old 
branches, where spurs are forming. 
Plantings of this variety are confined almost entirely to the deep, fertile, 
valley soils, and the annual heading back practiced with most varieties is 
rarely given the Agen. The customary pruning of the bearing trees consists 
in an occasional light thinning out of branches. No pruning at all is done 
for long periods in a large number of orchards. 
Where the new growth is severely headed back each year numerous thrifty 
shoots and twigs are produced, and the trees are vigorous and productive. 
The favorable response to severe heading back of the 1-year-old wood in the 
few examples which have been observed indicates the benefit, in larger sizes 
of fruit, to be derived by pruning trees that are making a poor growth (pi. 
16, C and D). 
Thinning sufficiently to admit light and to insure a thrifty growth of twigs 
should result in a good crop of large-sized fruit, but the compact growth of 
stunted branches will result in small fruit. 
CALIFORNIA BLUE 
Tree moderately vigorous, with broad, rounded, spreading, open top; pro- 
duces many spurs and maintains them well down along the old branches. It 
is inclined to send out but few secondary or fruiting branches, unless encour- 
aged to do so by being headed back, and produces new shoots from the terminal 
buds of shoots of the previous season (pi. 1, B, and pi. 17, A). 
When branches are cut back, vigorous shoots spring from immediately 
below the point of pruning, but these are usually few in number. They 
rarely spring from framework branches except under conditions very favorable 
to wood growth, and then usually at a point where a branch was removed, 
but almost never on unpruned or lightly pruned trees. ' On both severely and 
lightly pruned trees much of the growth of new shoots, aside from that which 
occurs immediately below the point of pruning, is from the terminal of the 
larger, unpruned branches rather than on spurs or twigs. On such trees 
many short branches and twigs grow from terminals of spurs and in all parts 
of the tree (pi. 17, B). In unpruned or lightly pruned trees few twigs grow 
from spurs, and these are shorter than on trees of most other commonly 
grown varieties of the domestica group. Unlike many varieties, the Cali- 
fornia Blue continues terminal growth of the larger branches for a number 
of years after pruning has been discontinued, if conditions are otherwise 
favorable to wood production (pi. 17, A). 
When the framework branches are numerous and have but few lateral 
branches they remain slender, but become longer by the continued terminal 
growth if not headed back and often bend badly with a load of fruit. Care 
should be taken to select strong, well-spaced framework branches and to prune 
so as to induce the desirable branching and to prevent too long a growth of 
the branches. 
If not irrigated, trees of fruiting age soon cease to make terminal growth 
except to form spurs, and the heading back of branches is necessary to main- 
tain sufficient vigor in the trees to produce profitable crops (pi. 1, B). 
The spurs are of the single-leader type, increasing their length from year 
to year. Some spurs finally reach several inches in length. When the spurs 
are young they branch but little, although branches may grow from any part 
of them ; and both the spur leader and its branches continue terminal growth 
if the tree is open and good growing conditions prevail. On trees which have 
been headed back in pruning, numerous spurs send out twigs or good-sized 
