7 ee 
LUTHER BURBANK 
acteristic of the tree—the extreme sensitiveness of 
its blossoms to the slightest fall in temperature. 
The apricot tree itself under proper conditions 
is relatively hardy and extremely productive. It 
is long-lived, and it attains great size. Moreover, 
it sends out a very extensive root system; demand- 
ing plenty of room, and justifying the demand by 
its increased production when the trees are not 
crowded. It continues to grow for many years, 
constantly extending its root system; so that some 
orchardists recommend planting the trees origi- 
nally twenty feet apart and then, after a number 
of years, as the trees increase in size, removing 
every other one, thus securing a forty foot space 
for the roots of each tree. 
In the matter of pests that attack it, the apricot 
is relatively favored. It is on the whole a very 
healthy and vigorous, as well as very beautiful 
tree. 
But the sensitiveness of its blossoms to the 
slightest chill has hitherto put a restriction upon 
the spread of the tree beyond the sub-tropical 
zones, except in such a territory as that of Cali- 
fornia, where, because of exceptional topograph- 
ical conditions, a sub-tropical climate prevails 
even at relatively high latitudes. There are ex- 
tensive areas of the middle and eastern states, well 
toward the north, where the apricot tree may be 
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