The leaves of my variegated hostas seem to turn all green in the summer. Why is this, and are there any varieties that don’t?
Beverly Wretman, Huntersville, NC
Cell mutations are responsible for many variegated hosta varieties, but they can be unstable.
Photo/Illustration: Jennifer Blume
Charles W.G. Smith, a horticulturist and contributing editor from Southfield, Massachusetts, responds: Hostas (Hosta spp. and cvs.) are valuable shade plants, in part because of the seemingly endless variations and patterns of white, yellow, gold, and green present in the thousands of available varieties. Ironically, it is the diversity of hostas that is partly responsible for some varieties’ changing color each summer.
The variegated patterns of hosta leaves are due to mutations of cells in one or more of the layers of the leaf. The mutations that produce variegation do so by altering the number and type of tiny organelles within the cell called plastids. Different types of plastids contain different-colored pigments. Chloroplasts contain chlorophyll and are green, while other plastids contain pigments that are orange, red, yellow, brown, or whitish to colorless. When a mutation occurs, the normal ratio of plastids is rearranged, some colors become more numerous, and the leaf takes on a characteristic variegated look.
The problem is that some mutations are stable while others are not. An unstable mutation can be affected by environmental factors, which can change the number and ratio of plastids in the cells. For example, sunlight can stimulate some plastids to change into different-colored types, while rapid growth can change the rate at which other plastids are produced in the leaf. Thus, the change in the number of plastids can change the color of the leaf.
The types of changes in leaf pattern resulting from varying levels of sunlight intensity can be diverse. A common change sees gold-leafed varieties with increased color intensity in brighter light and more muted color in deeper shade. Meanwhile, a variety that bears a streaky white central patch can quickly produce green leaves with a white margin, and plants with whitish or pale leaves can often darken into shades of green when exposed to more sunlight. Increased sunlight changes the plastids responsible for pale leaf color into the type containing chlorophyll, ultimately changing the leaf color.
Though changes in leaf pattern can happen in just about any hosta, some species and varieties seem more prone to variation than others. Perhaps the champion chameleon is Hosta ‘Undulata’. Varieties of H. ‘Undulata’ (syn. H. ‘Argentea Variegata’) have been around for a long time and are everywhere, like ‘Undulata Albomarginata’ with irregular white margins around a dark-green leaf, or ‘Undulata Univittata’ with wavy-edged leaves marked with a ragged central white blotch. These plants give new meaning to the word variety.
To minimize the chance of having your hosta change personality, I suggest the following guidelines: Select varieties with sharply defined leaf patterns rather than those that appear ragged or splashy; choose white or gold variegation along the margins of the leaf, as these are often more stable; and avoid planting variegated hosta in sunny spots, or even in very bright shade.