In the Garden Articles

Variegated Leaves

by Joan S. Bolton

Variegated plants have a way of sneaking up on you in the garden.

You might not notice them at first. After all, they don't usually produce big, in-your-face flowers or turn flaming red in the fall.

But look around and you'll begin to see them. They're the ones that bear leaves of more than one color -- usually a discreet edge of white, cream or yellow, but sometimes with unusual splotches, spots or irregular marks, and in red, purple, pink or chartreuse.

While they're not prized for their blooms, variegated plants are standouts year-round. When your more flamboyantly flowering plants take a rest, they'll still be there, stepping up to provide contrast and color in what might otherwise be an all-green garden.

What Makes a Variegated Leaf?

Ordinarily, leaves are generously endowed with the green pigment chlorophyll. Chlorophyll enables photosynthesis, the process by which plants absorb sunlight and convert the energy to carbohydrates.

The leaves of variegated plants are typically caused by a mutation. A portion of the leaves -- generally the outer edges -- loses the green pigment and the ability to photosynthesize sunlight. Fortunately, the remaining green tissue keeps the plant alive, although the plant is not usually as vigorous as its all-green counterpart.

Popular society garlic is an example. Clumps of the all-green species, Tulbaghia violacea, grow 2 feet tall and 3 feet wide, with prolific stalks of starry, lavender flowers rising 3 feet tall. Clumps of the variegated version, Silver Lace (Tulbaghia violacea 'Silver Lace'), top out at 1 to 1 1/2 feet tall and 2 feet wide. Silver Lace also blooms less profusely, with stalks reaching only 2 feet tall. Yet it's not less healthy: it simply doesn't grow as big.

In some plants, the absence of chlorophyll provides an opportunity for color other than -- or in addition to -- cream or white. Sometimes present is anthocyanin, a pigment that produces leaves in shades of pink, purple or red; or carotene, which produces yellow or orange-tinged leaves.

These rainbow pigments are present year-round, and are not to be confused with the process that occurs when deciduous trees develop fall color. That has to do with the trees converting starch in their foliage to sugar, to store in their branches and trunks as reserve energy for sustenance over winter.

These colorful pigments are also not to be confused with chlorosis, an iron deficiency that often afflicts citrus trees and causes the leaf veins to turn yellow; or disease, such as rose mosaic virus, which shows up as yellow zigzags and spots on rose leaves in spring and early summer.

In the Garden

Variegated plants come in all shapes and sizes, from creeping ground covers to full-size trees. They may also be traditional landscape shrubs, ephemeral bulbs, sturdy succulents, water-conserving natives and ornamental grasses. There are even variegated edibles: diminutive lemon thyme (Thymus x citriodorus 'Variegata') sports yellow edges on its tiny leaves, while Pink Lemonade lemon displays irregular yellow patterning on its leaves and green stripes on its yellow fruit.

Regardless of their character, variegated plants tend to be more delicate than their all-green brethren. As such, they especially enjoy all the conditions that most plants appreciate: fertile soil, decent drainage and sufficient irrigation, depending on their needs, which may range from desert-like to wanting to slurp at the water's edge of a pond or creek.

Many also welcome some shade, at least during the middle of the day. The reasons are several. Chlorophyll helps protect leaves from intense sunlight -- and the variegated plants' lack of it can lead to sunburn. Also, too much sunlight can stimulate the plant's latent desire to produce chlorophyll, which can bring on more green in the leaves, which has the potential to make the variegation fade or even disappear.

The good thing is that planting variegated plants in the shade helps bring color to areas of the garden where it might be difficult to get a flowering plant to bloom. In addition, the contrasting colors help provide a sense of depth in what might otherwise be a dark, all-green space.

On the other hand, some variegated plants do perform best in full sun, especially in protected areas along the coast. There, the play of light and dark on the leaves brings a sense of sun and shade, all on the same plant. The lighter-colored surfaces also catch the last hint of sunlight at day's end, and reflect moonlight at night.

Wherever your variegated plants land, don't try to boost their growth by applying lots of fertilizer. Too much nitrogen can pump up the chlorophyll at the expense of the variegation. And depending on your fertilizer, any nitrogen that the plants don't use can build up as salts in the soil around their roots. That, in turn, can cause the edges of the leaves to brown and curl. Salt burn is not a pretty sight.

Combinations

Repeating variegated foliage throughout your garden will help bring continuity to the landscape year-round.

Typically, variegated leaves look best paired up with plants that bear leaves in a solid color, such as all-green, all-blue, all-gray or all-purple.

For instance, spiky Silver Dragon grass (Liriope spicata 'Silver Dragon') looks fantastic with the olive-green and purple leaves of Chinese fringe flower (Loropetalum chinense).

Planting variegated plants side by side is trickier: the distinctive patterning on the leaves can get lost if there's too much going on with the neighbors.

For example, I once had someone suggest matching two variegated California lilacs (Ceanothus): shrubby, 8-feet-tall El Dorado (Ceanothus thyrsiflorus var. thyrsiflorus 'El Dorado'), which bears glossy green leaves edged in chartreuse, with ground-hugging Diamond Heights (Ceanothus thyrsiflorus var. griseus 'Diamond Heights'), which bears lime-green leaves with a hint of dark green in the center.

The vision was too gaudy for my taste. I prefer planting El Dorado with green-leaf natives, where the chartreuse edging achieves just the right subtlety; Diamond Heights packs the perfect punch when planted at the base of a dark-green hedge.

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Revolting Reversions

If solid green leaves appear on your variegated plant, snip them off at the base. Those all-green intruders are more vigorous and can crowd out the variegated leaves. In time, if you do nothing, your plant may revert to all-green.

Some plants are more prone to reversion than others. Certain varieties of New Zealand flax (Phormium) are notorious for reverting from their carnival colors to green. Look for flax that is labeled "stable."

Also, because variegated plants contain more than one type of genetically different tissue, their offspring may not look the same when grown from seed. Instead, variegated plants are usually propagated by leaf cuttings, division or tissue culture. That way, the new plants share the same mix of genes from the mother plant.

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Seeds of Wisdom

Use variegated plants in areas of your garden where the year-round color of their leaves will provide a consistent backdrop for flowers that come and go.