JoAnne Skelly: Why variegated plants revert to green

My friend Diane grows perennial flowers quite successfully in containers on her patio. She is good at it and grows a greater variety of perennials than I do. Recently, she pointed out a variegated plant called Glechoma hederacea, commonly called ground ivy or sometimes creeping Charlie. It is a member of the mint family. It is not the creeping Charlie often found as a houseplant. It is a hardy perennial that lives outside through the winter. She actually had two pots of this plant, one, as I said, was variegated white and green. The other was solid green. The green one was a cutting off the variegated plant and Diane had expected it to also be white and green. However, the variegated parent plant is now also sending off shoots of solid green. Diane wondered why and how this occurred.

A variegated plant is originally a cultivated variety started from a green parent plant with selective breeding. It may be a chimera in which the genes within the plant vary. Cell division, frequency of cell division and organization of cells mutate and cause the variegation resulting in colorless rather than green cells.

Diane’s plant may be reverting back to the original green. Why? One theory is that a variegated variety is not as vigorous as a green parent, because it has less chlorophyll. Chlorophyll is an essential component of photosynthesis, the process by which green (chlorophyll causes the green) plants manufacture the starches a plant needs for survival, a food of sorts, in the presence of carbon dioxide, water and sunlight. The plant may be struggling to get back to a stronger version of itself.

Diane’s plants are growing in semi-shade. Shady or semi-shady locations put variegated plants at a disadvantage. First, the plants have less chlorophyll and that is compounded by low light levels. Less light also produces less “food” through photosynthesis. A plant may revert to try to compete more efficiently, increase its harvest of solar energy and produce stronger growth. Changes in variegation can also be stimulated by temperature changes. Sometimes a waterlogged plant may revert.

Finally, variegation can be lost if the growth occurs in side shoots rather than in the tissues located in the tips of plants.

A possible solution to keep the leaves variegated is simply to prune out the newly developing green shoots. If that doesn’t work, Diane may want to enjoy her new chimera.

JoAnne Skelly is associate professor & extension educator emerita at University of Nevada Cooperative Extension. Reach her at skellyj@unr.edu.