Question
Hi, I have had a ponytail plant for 15 years. I live in southeastern PA just a few miles from the Delaware state line.  I always put it outside on an uncovered front porch in the summer.It gets sheltered somewhat from a saucer magnolia tree. I am getting ready to move it back into the house and I noticed a small area about the size of a quarter on the bulb that is above the dirt has gotten kinda soft and has a small crack in it.  
I have never had any soft spots on this plant before.  Could it be rotting from too much water or is it a disease?  Otherwise the plant looks great and grew a good bit over the season.  It's not a very big plant I haven't repotted it in years, roots are starting to stick through holes in bottom of pot. Total plant size from what's above soil is about 2 feet.  I'd say half the bulb is under the soil.  It's in a 10" x 10" round plastic pot with about 2 inches of soil between it and the ides of the pot all the way around.  Any thoughts on what could be causing the soft spot and if I should repot it now.  Thank you for your time.

Answer
Ponytail's are native to the dry Mexican climate, this habitat allows it to survive interior winter heat very well, as long the plant doesn't receive too frequent waterings, and never allow water to sit in the bottom of the saucer or pot. An interesting fact is that Nolina recurvata stores its water in its base.

A sandy-mix soil generally minimize the probability of root rot, especially compared to the peaty mixes normally used in most tropicals. Specifically, allow the soil to dry well between waterings, and if you have any doubt on whether or not to water the plant, skip it until the next week.

Dry, brown foliage, a shriveled stem or desiccated roots are usually signs of underwatering. If you are overwatering, we normally see light new growth, stem rot or root rot will appear.

Light requirements for ponytails are pretty easy to remember if you think of where it is native to - the Mexico deserts. Provide bright indirect light to full sun. Any window space - particularly one facing north will suit the light requirements of this high-light plant. For optimum performance, however, full sun is best.