In order to keep your ivy healthy, you need to keep a keen eye out for problems, including yellowing leaves. There are a number of possible causes for this condition, and ways to deal with them.
An ivy's leaves may turn yellow if it is being over watered and has "root rot," due to being in soggy soil. Ivies need to dry out between waterings, and over watering means the plant's roots are continually wet. Always use well-draining potting soil and make sure your pot has drainage holes in the bottom.
Inadequate lighting also can cause your ivy's yellow leaves. Try placing your plant closer to a light source to see if that helps its growth. Most ivies are tolerant of low-light situations; however, a constant lack of light can result in yellow leaves.
A lack of nitrogen in the soil or your fertilizer can also hurt your ivy, causing the yellow leaves. Try changing your fertilizer to one with a higher nitrogen content, as ivy's high concentration of leaves means it needs a lot of this. Ivy should be fertilized every month when it is actively growing.
If the roots of your ivy become too big for the pot then it will react to the cramped space with yellow leaves. Check the roots, if they are completely surrounding the soil, or there is little soil left, it's time to re-pot.
Ivy can be susceptible to spider mites, which cause the bottom leaves to turn yellow and fall off. Sometimes you can see webs on the leaves or stems. Misting, washing, lowering the temperature or using pesticides can help control these pests.