WINTER INJURY 



291 



Whitewashing and Shading. — Sunlight is an important influence 

 in forcing buds.^^" The spraying of peach trees with whitewash resulted 

 in a reduction of heat absorption, with the effects on blossoming shown 

 in Table 32, arranged from a similar table by Whitten. These data 



Table 32. — Blossoming Dates of Whitewashed Peach Trees^i" 



do not, however, show the full force of reduced sunlight absorption as its 

 effectiveness would be greatest during the warm periods of winter 

 while atmospheric temperatures are lower and when even slight develop- 

 ment may result in winter-killing. Somewhat similar results have 

 been obtained with plums in Ontario, but not with the apple, "^ which 

 blossoms much later when the air temperature has greater influence 

 in proportion to heat of insolation than it has earlier in the season. 

 Even farther south, because of the difficulty in keeping trees well covered 

 with whitewash and the consequent expense involved together with the 

 ever-present possibility of conditions that will kill buds despite the 

 covering, this method is little used. 



Board shelters have been found even more efficacious than white- 

 washing but again the expense involved precludes their use.^^*' However, 

 a choice tree or two can sometimes be located on the shady side of a 

 building to good effect and sometimes a hill can be of advantage in secur- 

 ing partial shade from the low midwinter sun for a good sized orchard. 



In General. — The peach has been used as illustrative matter here, 

 because it has been studied the most thoroughly. More or less similar 

 appHcation may be made to Japanese plums, apricots, almonds and 

 cherries. 



Finally it should be emphasized that the breaking of the rest period 

 in the buds is entirely independent of the roots and that efforts to retard 

 blossom development during warm periods in the winter by mulching the 

 ground to keep it frozen or by spreading snow on the ground around the 

 trees are absolutely wasted. Trees open their buds while the soil about 

 the roots is still frozen or after they have been cut away from the roots. 

 Time and again evidence to this effect has been presented and afterward 

 the same useless effort repeated. The winter rest period of buds can be 

 influenced through the roots during the growing season only. 



