502 CALIFORNIA FRUITS I HOW TO GROW THEM 



which come after the young fruits have made quite a growth are liable to do 

 more injury than the same degree of cold in the earlier part of the season, when 

 the fruits are less developed. At this stage of growth, 26 l / 2 to 27 degrees would 

 probably be dangerous to peaches. The very late frost of 25 degrees on May 4, 

 1912, killed practically all the peaches in the experimental orchard, while 24^4 

 degrees on April 17, 1910, left about 30% of the Elbertas. 



On the whole, apples and pears seem to be more resistant than peaches and 

 plums. This was strongly indicated in 1912, when practically all the peach crop 

 was destroyed on May 4, by a temperature of 25 degrees; while there was a 

 very heavy crop of pears and apples harvested the following fall. 



European and native plums seem to be slightly hardier than Japanese plums 

 and apricots, which are the least resistant of all the fruits included in the test. 



DELAYING BLOOM BY WHITEWASH 



Another suggestion conies from Missouri. It is concerning delay- 

 ing activity in deciduous trees by spraying with whitewash to reflect 

 heat the absorption of which by -dark bark causes the activity of the 

 tree to begin. Prof. J. C. Whitton of the Missouri Experiment Station 

 says: 



Purple coloring matter on untreated peach trees often absorbs heat enough 

 on a sunny cold day in winter to raise the temperature of the trees 25 degrees 

 or more above the temperature of the atmospehere. Whitened trees remain at 

 atmospheric temperature or usually a degree or so below. 



For ten consecutive years we whitewashed diagonal rows of peach trees 

 across the Experiment Station orchard just before midwinter. In this section 

 we had five general peach crops during that ten years on untreated trees; on 

 whitewashed trees of the same varieties we had eight crops. The five crops on 

 untreated trees were not all full crops; the eight crops on treated trees were all 

 but two full crops. More than double the amount of fruit was secured in ten 

 years on the whitewashed trees. The treated trees were anywhere from a few 

 days up to ten days later in blooming. In years when normal weather prevailed 

 until sudden warm spells brought the trees into bloom hurriedly, there was only 

 a little difference in time of blooming, and under normal conditions there was a 

 week or more difference in their blooming. This is less important, however, 

 than the fact that the whitewashed trees began their first starting into slight 

 growth on sunny days in late winter fully six weeks later than the naked trees. 



