Question
why are the  leaves on the pony tail palm turning brown on the bottom

Answer
Kathy,

It is not getting enough sun in the house during the winter months. If you can move it to a sunnier location that may help. Also cut back on the water for the winter. Indoors during the short days of winter it needs very little water. With too much water you risk root rot. You should only be watering every 3 weeks and only 1/3 the amount of water you gave it during the summer. Good luck.

Darlene