PLUMS IN RELATION" TO PRUNING 19 
The fruit spurs are large and strong and branch rather freely (pi. 10, C). 
They form at almost all nodes on 1-year-old wood and are very persistent, 
remaining thrifty throughout the tree for many years if given sufficient light 
(pi. 10, B). The branches of spurs are often short lived, owing to their heavy 
fruit production, but there is a succession of new branches replacing those 
which die. Spurs which are broken, even along the older branches, are often 
replaced by new ones if in a part of the tree which is exposed to light. Where 
the trees are headed back or the branches thinned to induce wood growth, one 
or more branches of a good number of spurs send out twigs several inches in 
length. These new twigs often appear along the old as well as on the new 
wood (pi. 10, D). 
When trees are thinned to admit light and only moderately headed back, 
the twigs which grow from spurs are more numerous but shorter and owing 
to the short internodes are more heavily leaved (pi. 10, A) than those on the 
long shoots of trees which have been severely headed back. 
The fruit is borne for the most part on leafy spurs which are 2 years old 
or older, if the trees are making a good growth or have been kept open; 
although on unirrigated or unthrifty trees many 1-year-old spurs are productive 
(pi. 10, E). On trees making a rapid new growth many 1-year-old fruiting 
spurs are leafless and die after the fruit ripens, but on trees growing some- 
what more slowly they usually retain their vigor, although bearing fruit. The 
1-year-old wood is inclined to fruit sparingly, and the fruit which appears is 
usually at nodes where spurs are forming, since spurs form at almost all nodes 
of the new wood. In shaded places, if the crop is excessive, many spurs along 
both twigs and older branches are leafless and die after the fruit ripens. 
As the variety is inclined to produce and retain a thick stand of vigorous 
spurs and spurlike twigs and these are inclined to be heavily leaved, only light 
cutting back is necessary to retain the vigor of the wood. 
Trees moderately vigorous, upright in growth, and produce both twigs and 
spurs. The vegetative vigor is confined largely to the newer wood, and most 
spurs and twigs die out as the wood becomes older. When branches become 
barren they usually remain so ; new spurs or twigs seldom appear on them. 
If the branches are severely thinned out or cut back or if growing conditions 
are otherwise made favorable, long new shoots sometimes grow from the older 
branches. 
The new shoots appear mostly on the stubs of headed-back branches, and 
but few grow on unpruned trees which are in full bearing. They are usually 
few in number, erect, and stout. The larger ones sometimes send out slender 
twigs a foot or so in length, and these produce numerous fruit spurs which 
if not shaded or crowded live for several years. 
The spurs are rather slender, brittle, frail, sensitive to shade, and for the 
most part short lived. If the tree is growing slowly because of drought or is 
kept open by the thinning of branches the spurs will naturally live much 
longer than where they are injured by the shade of heavily branched shoots 
such as grow on trees which have been severely headed back and whose new 
shoots have not been thinned. In the regions where summers are hot, most 
spurs of trees which are growing well die after two or three years ; but old 
trees which are growing slowly, especially if they have been lightly pruned, 
may retain some spurs for many years. To insure a good number of thrifty 
spurs, a good growth of shoots should be grown each year and these thinned 
out to admit light for spur development. Twigs often grow from spurs if the 
tree is kept open and has been encouraged to make wood growth by being 
headed back or otherwise. These, like twigs in other parts of the tree, develop 
many spurs and are also slender and make but little terminal growth. They 
are rather frail and require an abundance of light if they are to remain 
fruitful. 
In the cool coastal region of California, trees of the Kelsey variety which 
are severely headed back each winter are less vigorous than trees of most 
other varieties. The new growth is short, the new shoots in the tree tops 
often being less than a foot in length ; and the spurs are short lived, few of them 
living longer than two years if they bear fruit. In their poor growth in this 
region these trees compare well with Chalco, Gaviota, Wickson, and Occident, 
