Would four feet of good loose soil be enough for lemons?

Four feet of good soil, providing the underlying strata are not charged
with alkali, would give you a good growth of lemon trees if moisture was
regularly present in about the right quantity, neither too much nor too
little, and the temperature conditions were favorable to the success of
this tree, which will not stand as much frost as the orange.



Temperatures for Citrus Fruits.



What is the lowest temperature at which grapefruit and lemons will
succeed?

The grapefruit tree is about as hardy as the orange; the lemon is much
more tender. The fruit of citrus trees will be injured by temperature at
the ordinary freezing point if continued for some little time, and the
tree itself is likely to be injured by a temperature of 25 or 27° if
continued for a few hours. The matter of duration of a low temperature
is perhaps quite as important as the degree which is actually reached by
the thermometer. The condition of the tree as to being dormant or active
also affects injury by freezing temperatures. Under certain conditions
an orange tree may survive a temperature of 15° Fahrenheit.