Bright Variegation for Foliage Contrasts
by John Richmond
Some gardeners love variegated plants, collecting every one they can find, no matter how bizarre. Other gardeners loathe them, refusing to have any plant whose foliage is striped, streaked or blotched with white or yellow variegation. I like to steer a middle ground. Some variegation I wouldn't give garden room to. Other variegated plants are among my treasures.
Variegation in leaves is caused by a loss of light absorbing pigments in the plant cells. Remove only the green chlorophyll and the result is yellow variegation. Remove both chlorophyll and the yellow pigment xanthophyll and the variegation is white. Yellow variegated leaves are still quite efficient at using the energy of sunlight to produce sugars. Plants tend to grow a little more slowly but will usually tolerate the same conditions as their green leafed relatives. White variegated areas on leaves use none of the sun's energy. Plants with this type of variegation grow more slowly and are often far less vigorous than their plain leafed cousins. Many need shade to prevent burning of the white areas. In the wild they would soon die out but observant gardeners have gathered the best into cultivation. We can now enjoy a tremendous range - but not all are good.
What makes a good variegated plant is a matter of personal opinion. I loathe variegation that is blotched and spotted randomly across the leaf surface. Plants like the heavily spotted Aucubas, Abutilon x hybridum 'Thompsonii' or variegated nasturtiums look diseased to my eyes. I wouldn't waste garden room on them. I also abhor variegated forms of invasive weeds. Bishop's weed (Aegopodium) has a reasonably attractive white variegated form - but it's still an invasive runner. Variegated mints are no less invasive for having white edged leaves. Variegated horseradish or comfrey are even worse. If you wouldn't trust the parent in your garden, why trust its variegated offspring?
Some good plants are spoiled by excessive variegation. Euphorbia characias is a noble plant with great heads of lime green flowers in late spring. Recently, a heavily white variegated form has come into cultivation. Compared with the original it lacks all grace and elegance, even if it does stand out against a dark background. Plants with heavily cut leaves are rarely enhanced by variegation. Geranium phaeum, the mourning widow geranium, has a form where an irregular white edge to the fresh green leaves spoils the effect of the dark petalled flowers. I grow the type - but won't grow the variegated form.
What I most enjoy is plants whose simple leaves are enhanced by broad streaks of white or yellow. Grassy leafed plants, broad-leaved perennials, plain leafed shrubs, all look good with bold variegation.
I love variegated irises. Striped in white, yellow or a combination of the two, the vertical shapes of the leaves are enhanced by the lack of pigment. My favourite is Iris foetidissima 'variegata'. It rarely flowers, but the evergreen leaves are at their whitest in winter when a good clump is a thing of rare beauty. Others, a variegated bearded iris, white striped iris laevigata in my pond, and yellow striped, yellow flowered flag iris have the bonus of attractive blooms and long lasting foliage interest. Be careful with the last one. It seeds freely and seedlings do not come variegated.
Grasses, sedges and bamboos are grown mostly for their foliage and anything that enhances that effect is worth having. Many of the varieties of feather grass, Miscanthus sinensis, have white variegation that complements their graceful growth. Hakenechloa macra 'Aureola' is built on a lower scale but has white and yellow stripes on the arching tufts of leaves. Vivid yellow streaks on the 3-ft tall bamboo, Arundinaria auricoma, make this a superb border plant. Carex morrowii 'Oshimoensis' has bright yellow midrib variegation on its low growing evergreen leaves. With me the brightness lasts all winter.
About the Author John Richmond is a keen gardener who lives and works in the South West of England. He has a scientific background as a professional ecologist. He has written occasional articles for gardening and other magazines in Britain since 1984, specializing in garden wildlife issues and hardy plants. His own garden can be visited via the web, and correspondence