In most cases, less than 5% of citrus blossoms will actually develop into
mature fruit. An overwhelming number of
the blooms naturally drop from the tree during bloom and shortly thereafter.
This is a natural thinning process. Once
the tiny fruit has reached about 1 inch in diameter they tend to stay on the
tree. After this point, if fruit continue
to drop, it is due to some type of environmental stress. Here are several possibilities: nitrogen deficiency or excess, sudden high
temperatures, a lack of water or too much, a heavy
insect/mite infestation, hot dry winds, air pollution and severe pruning. Constant rain
during the bloom period can also stress the tree. Any one of these factors that occurs around the time
of bloom can cause the flowers and young fruit to drop.
The question may arise, “Why does one citrus variety drop its fruit, but other
varieties in the same garden do not?”
Here are some of the more common answers.
1. Different citrus varieties obviously
have a different genetic composition.
Consequently, the various varieties will react differently to the
numerous stresses.
2. In the same manner, citrus trees are normally
budded or grafted onto different rootstocks. These various rootstocks will react
differently to the many diverse environmental conditions.
3. And lastly, although difficult to observe,
some locations in the garden may be more conducive to plant growth: better soil
drainage, greater soil fertility or more protected from dry wind and high
temperatures.
