iThe Canadian Horticulturi^ 



''ol. XXXII 



APRIL, 1909 



No. 4 



Why Wc Prune* 



Prof. J. C. Whitten, College of Agriculture, Columbia, Missouri 



'N the management of fruit trees 

 perhaps ho other factor is of greater 

 interest or more significant than that 

 each section of country has a shape or 

 Ideal of its own to which each kind of 

 jfree is made to conform. We are struck 

 by the differences between the low-grow- 

 Hng fruit trees of the central-west and 

 the lofty ones on the Atlantic coast ; we 

 contrast the dense heads, or branching 

 system, of the west, and the more open, 

 or spreading heads of the east. Still 

 more striking are the espaliered trees of 

 Europe, whose limbs are often trained 

 like the ribs of a fan, in flattened form, 

 upon a trellis or against the sunny side 

 of a wall. Each of these different systems 

 of pruning or shaping is a means of 

 adapting the tree to its environment. 



ADAPTING TREE TO ENVIRONMENT 



In the foggy climate of western 

 Europe it is desirable to admit all possi- 

 ble sunlight to the parts of the tree. The 

 thin, open head exposes the fruit buds, 

 flowers and ripening fruits to the favor- 

 able influence of the sun, thereby fur- 

 thering what is secured in part by plant- 

 ing the tree on a south slope or on the 

 sunny side of a wall. 



In the dry. sunny, continental climate 

 of the central-west of our country, a sys- 

 tem of pruning quite oposed to that of 

 western Europe is employed. Through- 

 out the prairie section especially one is 

 .struck by the low, dense heads of the 

 fruit trees. The trunks of the trees are 

 usually from one foot to three feet hip-h, 

 thus securing low heads or branchine 

 systems. These low heads help to insure 

 the trees against injury from prairie 

 winds. They lessen the number of wind- 

 falls among the fruit. They shade the 

 ground under the trees and prevent undue 

 loss of moisture from the soil. Their 

 shade keeps the soil from becoming too 

 hot during inten.se sunlight in summer 

 and opposes sunscald, which sometimes 

 injures the exposed trunks and main 

 limbs of high headed, open branched 

 trees. Low heads also, in some degree, 

 retard the blos.soming period, rendering 

 the flowers less liable to injury from 

 spring frosts, which here so frequently 

 follow the first warm, sunny days of 

 early^ .spring. The den.ser branching 



• An adrtrcBs delivered at the last convention of 

 iiri Illinoix .State Horticultural Society. Its principlOR 

 , may be applied in the orchards of Canada. 



system aids in accomplishing the same 

 purposes which are sought through the 

 adoption of the low head. 



In the various sections of the world 

 where fruit growing is carried on, some 

 intermediate form between the two above 

 extremes is adopted to adapt the height 

 and density of the head of the tree to 

 climatic influences. Near the Atlantic 

 coast, where there is brighter sunlight, 

 more wind and less moisture than in 

 western Europe and yet less sunlight, 

 less wind and more moisture than in the 

 continental climate of the west, the mid- 

 dle ground is adopted with respect to 

 height and density of the head of the 

 tree. 



In extreme continental climates, the 

 low. dense head is in keeping with the 



Ten Years in Advance 



I am glad that The Canadian 

 Horticulturist devotes more 

 space than formerly to the grow- 

 ing of flowers, in which I am 

 much interested. I am sending 

 $5.00 for my subscription up to 

 the end of igi8. — Mrs. P. E. 

 Harvey, Toronto. 



selection of a north or east slope for the 

 orchard. This is an interesting contrast 

 to the south slope, or sunny location pre- 

 ferred in western Europe. 



FUNGOUS diseases AND PRUNING 



In recent years attention is being given 

 to shaping the tree so as to oppose 

 fungous diseases. Leaf rust, fruit scab, 

 many of the rots and many other mala- 

 dies which affect fruit trees are now 

 known to be due to parasitic fungi that 

 attack the parts of the tree or its fruits. 

 Many of these parasites thrive better in 

 cool, damp, shady places than they do in 

 sunlight, just as molds develop in cellars 

 or damp places. In a foggy, humid cli- 

 mate the high, open head admits sun- 

 light and air and opposes the develop- 

 ment of these diseases. In a dry, sunny, 

 or windy location it may not be neces- 

 sary to maintain an open head to secure 

 enough sunlight and aeration. 



wood growth and fruitfulness 



In connection with pruning it should 

 be borne in mind that other factors than 

 73 



merely shaping the tree to adapt it to 

 climatic conditions must be taken into 

 consideration. Fruit trees may be said 

 to expend their energies in two ways— 

 by producing wood growth and by pro- 

 ducing fruit. It is a well known fact 

 that a fruit tree may sometimes grow 

 with exceeding luxuriance and fail to 

 produce fruit. In fact, too much wood 

 growth and leaf growth is opposed to 

 fruitfulness. The orchardist often says 

 of a vigorous tree that it is "running to 

 wood growth" instead of to fruit. Any- 

 thing which tends to check this exces- 

 sive vegetative activity usually throws 

 the tree into bearing, or favors reproduc- 

 tive activity. On the other hand, the 

 production of a heavy crop of fruit 

 opposes excessive wood growth. 



A proper balance between vegetative 

 and reproductive activity (or wood 

 growth and fruit production) may in part 

 be maintained by proper pruning. If a 

 tree is pruned by cutting back or by re- 

 moving some of its branches in winter, 

 its wood growth will be accelerated dur- 

 ing the following growing season. If a 

 part of the buds which normally would 

 have been pushed into growth in spring 

 are removed, there will be correspond- 

 ingly greater growth from the fewer 

 buds which remain. If this length 

 growth is excessive, and if it continues 

 too late in the season, few or no fruit 

 buds may be formed for the next year's 

 crop. As a rule, length growth of limbs 

 is continued at the expense of diameter 

 growth and storage of plant food in the 

 twigs and buds. Fruit buds usually 

 begin to form in early summer, for the 

 coming spring, about the time rapid 

 growth ceases. The maxim, "prune in 

 winter for wood but in summer for fruit" 

 is an old one. 



Cutting out or shortening limbs in 

 summer, when the leaves are elaborating 

 plant food, usually checks wood growth 

 and thereby often favors the formation of 

 fruit buds. Whether to prune more in win- 

 ter or in summer depends much upon the 

 vigor of the tree. If vegetative activity 

 is weak and the energies of the tree too 

 low for the maturity of a good fruit crop, 

 winter pruning tends to increase its 

 growing energy. If the tree is making 

 too luxuriant wood growth, summer 

 pruning (checking this growth) may re- 

 sult in the formation of fruit buds. 



