Question
The leaves of my Lily of The Niles are turning yellow.  What could this be caused from?

Answer
Hi Alene,
Thanx for your question.  There are a number of reasons the leaves of the Lily of the Nile (Agapanthus) are turning yellow.

Too much water:  make sure soil is free draining.  If in a pot, make sure there is adequate drainage and no standing water.
Not enough water:  rare but might occur in pots.  Water every day in hot climates.
Lack of nutrition:  Feed with a 12-12-12 balanced fertilizer following application instructions on the package.  Available at most garden centers and nurseries.
Is the plant in full sun?  Too much shade will cause this too.  I hope this helps.
Tom