Avacado plant backing please?

i have an avacado plant and it's over a foot towering. the leaves closest to the bottom are turning brown and dry. what does it mean? i read that if i'm over watering they will turn sickly. i don't want to keep plucking them rotten until there are no leaves disappeared!!! help!!
Answers:    It's that time of year. Avocado trees are almost evergreen, but can shed leaves if it get cold or dry. They also tend to shed leaves during the blooming phase, which occurs surrounded by winter and early spring.

My neighbors hold avocado trees that almost completely shed their leaves each winter, while the fruit is still slack off the tree. Then, after the flower buds appear, the leaves come vertebrae.

Regarding watering, most plants grow so much slower in winter (colder temperature, lack of sunlight) that what would be a regular watering routine within summer would be severe overwatering in winter. This cause the roots to rot, killing the plant. And, the indication of this is yellowing of the leaves formerly they drop off.
Are you pinching the current top leaves off contained by order promote lower growth? Might also want to attach a small amount of fish fertilizer to the water. Overwatering is not what they resembling either. Could also necessitate potting up to a larger sized pot.