Variegated plants can revert or turn green for a number of reasons. It can be a reaction to extremes of hot and cold or a reaction to low-light levels.

Why are my variegated hostas turning all green?

According to Bob, nutrients have no bearing on this gradual color change. This reversion to green is called viridescence and is a physiological response to warm summer nights. In regions where the nights are cool, the leaf color of ‘Albomarginata’ hosta remains unchanged.

Why are my hostas losing color?

Once the growing season dies down, hostas will naturally begin to enter dormancy. When this happens, you may notice yellowing hosta leaves. This is perfectly normal and nothing to worry about. Once the leaves have completely died back in fall, you can cut the plant back.