Monday, September 23, 2013

Citrus Fruit Drop

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.