LUTHER BURBANK 
tree that naturally blooms late enough to avoid 
these frosts. 
This is especially important in view of what 
has just been said about frosts waylaying trees 
on a southern exposure, because precisely such ex- 
posure is of value at the other end of the season, 
to hasten the ripening of the fruit. This is not 
only important in the case of fruits designed to 
meet an early city market, but it applies to many 
varieties that tend to ripen late in the fall and 
which thus may suffer from the early frosts of 
autumn. 
It should be recalled that the warm southern 
exposure also tends to take the moisture from 
the soil early in the season, so varieties planted 
in such a location should be able to resist drought. 
Trees planted on a hillside will probably have 
natural drainage. Otherwise it may be necessary 
to drain the soil with tile or with open ditches, or 
else to select varieties of fruit that are known to 
thrive in a moist, cool soil. Such varieties must 
necessarily have an unusually large leaf surface 
and shallow root system. For this reason they 
should not be placed where they are subject to 
heavy winds. 
What may be called air drainage is sometimes 
quite as important as water drainage. Cold air 
flows down the hillsides and settles in the valleys. 
[64] 
