I’ve had this plant for 9 months now. Leaves used to be a bright green. I water it moderately every couple of weeks. Lately it’s turned yellow and wilting. Leaves are no longer sharp. which means either under watering or over watering but I can’t tell which it is. Do you mind taking a look and advising? P.s. I was at the bessarian station library last night and thoroughly enjoyed the caring for houseplants session.
Thank you for contacting Toronto Master Gardeners with your question.
Most Yucca palms sold as houseplants belong to the species, Yucca elephantipes, a plant native to dry areas in the southwest United States, Mexico and Central America. It is very drought-tolerant which can be a great advantage in a houseplant. It can, however, be overwatered very easily. This is the most likely the problem with your yucca. These plants also thrive in bright light conditions. It is difficult to tell from your photo, but it is also possible that your plant is not getting enough light. Bright, indirect light is best.
It is normal for older plants to begin to drop their lower leaves. Some hold onto the leaves but they droop. This could be what is happening to your plant, but the yellowing of the leaves suggests the over-watering scenario. Normally, under-watering is indicated by browning leaf tips. Water requirements can vary with differing indoor conditions but a general rule of thumb is watering every week or two in the spring and summer (during the growing season), and every 2 – 4 weeks in the fall and winter. Your watering program sounds reasonable for summer. I wonder if there has been any standing water in the pot or drainage saucer? That can be particularly problematic for these plants because they store excess water in their stems/trunks. The potting soil used should also promote good drainage, and, as with all potted plants, a pot with multiple drainage holes is important.
I hope these suggestions help to identify and correct the problem with your yucca. You may wish to consult these 2 online articles: this article from Spruce and this one from My Garden give some good, general information on the care of yucca houseplants.