Did the leaves turn yellow before they dropped? If so it could indicate that the plant was getting too much water. The soil can dry out a bit before it is rewatered.

You can change the soil and repot the tree if you like, and then place it in a sunny window. Water with a weak fertilizer and you should shortly see new growth once it adjusts to the new soil.

Good luck with your avocado.

Trudi

I have an avacado about 1 year old, four foot high. Transplanted into the garden 4 months ago...took off fine then leaves started burning up on the edges like a torch applied around the edge of leaf, no yellowing...then leaf falls off after a time.
Plant is in full sun, 90-100 degree days, 80-100% humidity on a normal day. You can see huge avacado trees in town here producing fruit, so it is not impossible. Not enough water ???? Is there a mexican variety that perhaps is better suited to south Texas ??? any suggestions.