Q: How do you keep variegated leaves variegated? I have a green spiderwort with white variegation. It looks very healthy but the leaves going all green. I have an acid-green heuchera but it too is going darker.

A: Variegation or other unforseen changes in leaf color are most often caused by genetic mutation: a leaf bud gets damaged by a cosmic ray or a chemical aberration and it then produces cells that aren’t the same color as the parent plant or branch. Some are stable traits that seem never to change back to their different-colored origin. Others are less stable and weakly or strongly revert to “look like Mama looks”. I’m sure you’ve seen a variegated privet hedges with patches of dark green in the light green foliage.

In evolutionary terms, lighter variegation does a plant no favors, since lighter cells don’t photosynthesize as much as darker ones. My guess is that your plants are slowly reverting. The best way to deal with it is to clip out unwanted leaves at the base and give the plants enough TLC to make it produce new leaves from the variegated part of the crown.