PLUMS IN RELATION TO PRUNING 15 
poorly they are often unbranched and are more slender and more easily 
broken than elsewhere. Under conditions favorable for wood growth, many 
spurs along the larger branches grow to twigs, and in this way and by being 
killed with shade from the dense tops, many spurs or twigs in the interior of the 
tree are lost if the tree has been regularly and heavily headed back. On 
such trees the development of new spurs may often be induced by removing 
branches to admit light, as the older wood retains its vigor well (pi. 4, C). 
Fruit is borne on spurs of all ages throughout the tree and at nodes of 
1-year-old twigs. "Where the tree has been kept open and the crop is not 
excessive, almost all fruiting spurs produce leaves ; and the fruit on 1-year- 
old twigs is usually at nodes where spurs are forming, which indicates the 
strong vegetative vigor of the variety. 
This variety is very prolific and bears regularly, producing fruit in all 
parts of the tree. Unless twigs, branches, and fruit are well thinned out, the 
fruit will be small and much propping of branches will be necessary when 
the fruit approaches- maturity. As branches are inclined to be slender, 
heavy crops cause them to bend and expose fruit to the sun ; and as the fruit 
is easily sunburned, the loss from this cause is considerable, unless trees with 
strong rigid branches have been developed. 
BUEBANK 
Tree open, spreading, very vigorous, branches freely, and forms numerous 
spurs which are retained over a period of years (pi. 5, A). 
Spurs form at almost all nodes of 1-year-old shoots and twigs and, if not 
injured mechanically or by shade, remain thrifty and productive for many 
years. The spurs form many short branches but no decided leader, and they 
remain rather short, broad, and compact. Where light permits, they are heavily 
leaved and the leaves are long and large, indicating natural vigor (pi. 5, B). 
Heavily fruiting branches of the spurs sometimes die after harvest, and new 
ones rarely appear in their places. Where wood growth is considerably en- 
couraged by pruning or where a part of the spur is removed, a branch of the 
spur will often grow to a slender twig. These twigs produce spurs and bear 
fruit well but usually remain short and slender. The basal portion of the spurs 
is very strong, but the branches of spurs break easily at the termination of a 
year's growth. Many branches of spurs and slender twigs which grow from old 
spurs are therefore brohen by strong winds or through harvesting the fruit. 
If trees are thrifty and sufficiently open to admit the needed light, spurs which 
have been broken off are often replaced by new ones even along the older wood. 
With this variety, as with others, heading back causes a rank growth of new 
shoots just below the point of pruning, and differing from most varieties these 
shoots radiate outward in all directions, forming an almost spherical tree top 
(pi. 6, A and B). If, in pruning, the tree is thinned out well each winter and 
only moderately or lightly headed back, fewer long shoots and slender twigs 
grow from spurs than in a heavily headed-back tree, and a greater proportion 
of the new growth is short and stocky. In this case the spurs are retained 
throughout the tree and are vigorous and productive (pi. 7, A). With no 
pruning, few new branches are produced, and these are usually short and frail 
if growing conditions are not above normal. The fruit is small and usually 
unprofitable on such trees. 
Almost the entire crop of fruit is borne on spurs with leaves or at nodes of 
1-year-old wood where spurs are developing. This shows a decided tendency to 
produce and retain spurs (pi. 6, A, and pi. 7, B). Considerable fruit develops 
on 1-year-old twigs and more on the large 1-year-old shoots than is common 
with most varieties. This, with the strong growing tendency, indicates the com- 
bined vegetative vigor and fruitfulness of this variety. 
After a strong framework and numerous secondary and fruiting branches 
have been formed, the naturally open body of the tree should be kept well open 
and outer branches cut back and thinned moderately to maintain the needed 
vigor but not sufficiently to cause a compact tree. The removal of some of 
the more slender twigs, on which the fruit is often small, will not only admit 
light to the spurs below but prove an effective method of thinning the crop. 
By developing vigorous spurs throughout the body of the tree, regular crops of 
good-sized fruit may be expected. 
The uniformity of growth and production under different temperatures and 
cultural conditions is more marked with the Burbank than with most other 
