There are over 45 named species of yuccas, drought-tolerant plants sometimes classified as succulents and popular for their ease of care, long leaves and tall clusters of white flowers. Some yuccas are cultivated to look like trees, while others grow as small, bushy shrubs. All thrive in arid climates, making them excellent desert landscaping plants. Regardless of the species, yuccas can suffer from a number of problems, often signified by yellowing of the plant's leaves.
Note the location of the yellow leaves. Yellowing on the crown of the yucca plant leaves can indicate too much sun. This is especially true for yucca houseplants placed right beside a hot, sunny window. Yucca plants, although sun lovers, can be scorched by the sun. Yellowing leaves on the bottom of the plant may indicate insufficient sun.
Examine the yellow leaves. If you see tiny bugs on the leaves, the plant could be suffering from an insect pest infection, although pests usually cause leaves to wither and turn brown. Yellow spots on yucca leaves often signify a fungal infection. These spots will spread, turning all the leaves yellow.
Prune the yellow leaves. Once the leaves turn yellow, they are not going to recover. Instead, they will wither and die. Yuccas are tough plants that can tolerate severe pruning, so go ahead and cut off all the yellow leaves. Not only will this improve the look, but if the yellowing is caused by a fungus, it will prevent its spread.
Dispose of the leaves in a trash bag. Do not let them sit on the ground underneath the plant. If the leaves are infected with a disease or fungus, it can overwinter in the soil and infect the plant again in the spring.
Prevent the problem from returning. If no signs of insects or fungi are evident, chances are your yucca is either sunburned or has been overwatered. Overwatering will cause the leaves of a yucca plant to turn yellow. Let the soil become moderately dry between each watering. If the leaves continue to turn yellow, let the soil dry out even more. If you believe the problem is insects or fungi, spray your yucca with an insecticide or fungicide and, if it is potted, re-pot in new soil.