i have 4 different varieties of avocado growing in my garden. all of them flower and fruit, apart from the biggest one.

Question

Every year it flowers prolificly and the tree starts to lose its leaves, and over the next few months all the leaves will die and drop off and most of the blossoms with it. Then it shoots new leaves and is back to normal by Christmas. Can you tell me what is wrong with it? It has never been pruned and gets exactly the same attention as all the other avocados.

Answer 1

It may be a cultural issue or something associated with that particular variety, since you say they are all different. It may be leaf burn which can happen as a result of too much salt in the soil or irrigation not reaching far enough to the dripline. Or maybe that tree gets more sun than the others. The leaves would drop then return like yours do.
Here is more information:

https://www.gardeningknowhow.com/edible/fruits/avocado/avocado-tree-with-no-fruit.htm
https://www.gardeningknowhow.com/edible/fruits/avocado/what-causes-avocado-leaf-burn.htm
https://www.gardeningknowhow.com/edible/fruits/avocado/avocado-pests-and-diseases.htm