PLUMS IX RELATION TO PRUNING 25 
small leaflets and which die after fruiting, the same as do leafless spurs (pi. 
21, D ) . It is rarely produced on the long new shoots which grow after the 
tree has been heavily headed back, although when this wood is 2 years old it 
bears heavily on the twigs and spurlike growth produced the previous year. 
If little or no pruning is practiced, the new growth is slender and of only 
moderate length, and the tree soon becomes spreading or drooping from carry- 
ing loads of fruit. On account of their strong vegetative vigor, however, trees 
of this variety which are irrigated and growing in fertile soil remain thrifty 
and produce regular crops of good-sized fruit where but lightly pruned (pi. 
22, A). If heavily cut back, very rampant shoots spring from near the point 
of pruning (pi. 22, B). These new shoots have large, heavy leaves and cause 
a dense shade in the center of the tree. Where water for irrigation is lacking, 
especially on soils low in fertility, the growth following pruning is only mod- 
erate, and considerable cutting back is necessary to insure the needed new 
growth. Under the latter conditions, little or no pruning results in short 
wood growth and therefore restricted bearing surface and often in small 
fruit (pi. 22. C)*. 
Under conditions favoring a moderate wood growth, this variety is more 
inclined to produce twigs from the terminal buds of its twigs and branches 
and less inclined to retain lateral fruiting spurs than almost any other of 
those commonly grown in the Pacific States. The Italian Prune is among the 
possible exceptions. The Agen (French prune), which is thought to be one 
of the parents of the Giant, resembles it closely in that the new growth de- 
velops from the terminal buds ; and the variety thought to be the other parent, 
the Pond, resembles it closely in its tendency to retain no fruit spurs. 
For a pruning method, light thinning of interfering branches, the cutting 
back of some of the long bending branches which require props when fruiting, 
and the removal of branches to admit sufficient light appear to bring satis- 
factory results where orchards are irrigated and the soil is at least moder- 
ately fertile. The cutting back of long drooping branches and training to de- 
velop strong upright leaders is particularly desirable on the fertile, deep, irri- 
gated soils where there is a strong wood growth. On unirrigated soils con- 
siderable cutting back of both new shoots and fruiting twigs is required to 
maintain the thrifty wood growth needed for the development of large fruit. 
GOLDEN DKOP (SILVER PRUNE) 
Tree upright spreading, open, only moderately vigorous, very sensitive to 
shallow soil and drought, and branches but little except for the growth of 
fruiting twigs and spurs. It is probably less inclined to send out new shoots 
from the terminals of the previous year's shoots than any other variety studied. 
Of the more distinctly spur-producing varieties, it is less inclined to retain 
spurs or to replace those which die or are broken off. 
The new shoots spring from near the point of cutting back of the branches, 
but they seldom grow from the old wood unless induced to do so by pruning. 
When old branches are shortened the ' new shoots, which are usually short, 
grow from terminals of vigorous spurs just below the point of pruning. Cutting 
back new shoots causes an occasional spur to produce a twig or short shoot, 
but aside from this the spurs make only a short annual growth (pi. 23, A). 
Thrifty spurs grow to considerable length the first summer, and if the tree 
is growing well they increase in length each year (pi. 23, B). They often 
produce several" branches, and under good growing conditions one of the 
branches may grow to a twig or longer shoot. In this case the other spur 
branches perform as normal spurs. The spurs are very sensitive to shade. 
They form in good number along the -1-year-old wood, or if this wood is above 
the normal in vigor fruiting twigs develop instead of the short spurs found on 
less vigorous shoots. These twigs produce both terminal and lateral spurs 
in their second year. Although the spurlike twigs remain vigorous and prolific 
for several years, the short spurs usually disappear within a few years (pi. 
23, C). On large vigorous branches spurs have been found on 15-year-old 
wood ; but on the more slender branches, where they are usually short and 
slender, they often disappear after their first crop bf fruit has ripened. This 
early dying out of spurs leaves the many barren branches found so commonly 
in the Golden Drop (pi. 23, D). 
The Golden Drop is inclined to bear fruit on alternate years. The slow wood 
growth made during years of heavy crops is inclined to be unfruitful the 
following year, and the vigorous wood growth made during seasons when the 
