Q. Just this last year we have had very little fruit on our Kumquat whereas prior to that the tree was ample with fruit. The tree appears to be healthy, just no fruit. The only difference I can think of is that in previous years I covered the tree whenever the temperature was below freezing. However, this past year I only covered it when the temperature fell to the upper 20’s.
A. Kumquat is a very winter hardy citrus and can survive most winter temperatures here without any problems provided it is in a sheltered spot. It is considered one of the most cold tolerant of the citrus. The key question you have to ask yourself is whether it produced any flowers or not this past year. No flowers equals no fruit.
The major reasons for early fruit drop are temperature and irrigation problems. If we have freezing temperatures or if the plants become water stressed from not enough water, they tend to drop fruit and flowers if they were produced. Flower buds and fruits are much less hardy to freezing temperatures than the plant itself.
Kumquat may produce fruit all through the year but tend to produce fruit in the spring and fall months and through the winter. If it does get some winter damage, you would have seen plant dieback.
When dieback occurs, the plant will regrow to the height it was before it had damage and produce very few flowers. Once it reestablishes its previous size it will then begin to flower again and produce fruit.
If there were some spring freezes the flower buds would be killed before anything else would show any damage. This would tend to minimize fruit production. If the plant receives a lot of fertilizer, particularly nitrogen, it may tend to put on new growth with few flowers and of course very little, if any, fruit.