A yucca plant is a hardy annual that thrives with little maintenance. It also produces a wonderful spray of white, bell-shaped flowers (even though they don't last long). In many cases of dying yuccas, the problem is too much attention or not enough light.
Tip: Spider mites are a common problem with indoor yuccas as well. If you notice the tiny red mites on your plant, take your potted yucca outdoors or into the shower and spray well, including the underside of the leaves. A spray of dish soap and water will control bugs and mites.
Yuccas grow well indoors and can often extend themselves above the natural light coming through a window. The first sign of a light problem is when the leaves become a richer green as the plant produces more chlorophyll to take advantage of what little light there is. When the leaves are no longer in the direct light, you might not spot this color change, however.
This is followed by a yellowing of the leaves as they fail to produce the level of food necessary for the roots. The yellowing is caused by the plant trying to remove toxins that have developed. The leaves will then droop and die off. While the leaves are still alive, this situation is very quickly resolved by putting the plant in a position where the leaves are in full sunlight again.
The yucca is very susceptible to various kinds of rot and as such, needs to be in well-drained soil. The quality of the soil does not need to be high, as long as it's loose. Overwatering can lead to yellow leaves, a spongy trunk, and root rot.
Allowing the plant to dry out will cause a rapid recovery. If your yucca is in a pot without drainage, it must be repotted into one that does drain. Sometimes, having too large a pot can also have a similar effect, because the soil stays moist for too long. Most yucca plants can cope with about an inch of soil around the base of the trunk.
A major problem caused by overwatering is root rot. If the roots have turned a brown color instead of being pale, they have gone too far to recover. Remove the rotted roots by cutting the trunk so that you remove all signs of rot. The part of the trunk that is left, if it has sound roots, can be repotted into dry soil and allowed to recover before being watered again.
The trunk of the yucca can hold a lot of water and will do so, but this is a survival mechanism. If the trunk stays wet it will rot and grow very spongy. A tall yucca will start to lean and may even collapse as the trunk loses strength, so before watering your yucca, always check that the soil is dry.
A yucca tends to do better in a constant temperature when grown indoors. If your yucca is in your garden, it will be able to tolerate a wide range of temperatures, but indoor yuccas like warm, dry air and lots of ventilation.
As long as you water it only when it's dry and keep it in direct sunlight, your indoor yucca should remain healthy.