When little is in flower, gardeners turn to variegated leaves to provide winter interest. Two-toned or bicolour leaves are relatively rare in the wild. Variegated Holly is just one seasonal horticultural option. Variegation is found at the leaf margins in Holly. This isn’t the case in all plants. Some plants go for a more mottled effect. Others even have 3 or 4 colours.
Variegated leaves have an irritating tendency towards reversion for gardeners. Green highlights the presence of nutrient-producing chlorophyll in a leaf. Plants need chlorophyll for photosynthesis. Its partial absence in variegated leaves makes them less efficient at generating energy. A totally white leaf is redundant. Such albino growth will not survive. The pretty variegated leaves desired by gardeners do not present a desirable situation for the plant itself.
Totally green leaves on a variegated plant can be larger and more vigorous. Variegation is the result of a mutation or virus that plant breeders have encouraged. Variegated plants are not stable. In order to prevent reversion, gardeners have to cut out any green leaves from their variegated plants. If left to their own devices, variegated plants become untidy and lopsided with green leaves rapidly taking over.
Variegation in the Garden
Another plant associated with Holly at Christmas and often found in variegated form is Ivy. The choice of variegated plants for gardeners is seemingly endless: variegated Dogwood, Salvia, Nasturtium, Phlox, Iris, Columbine, Sage, Hostas, Euonymus, Euphorbia, Begonias, Weigela, Agave, Abelia, Elaeagnus, Cyclamen, Phormium, ornamental grasses, etc.
Variegation in the Tropics
It is possible to find variegated leaves in the tropics in the rainforest understory. Many of these plants are familiar as house plants. Variegation seems to act as a form of camouflage in exposed positions. New, vulnerable leaves have a higher degree of variegation. Older leaves seem to lose their variegation. Check and compare your variegated house plant’s leaves.
The more you learn about plants, the more astonished you become. Plants cannot shift their roots and move away to resist attack from insects. They are not without ruses. Researchers are still working on understanding them. The absence of chorophyll in irregular patterns can suggest the presence of leaf miners. Variegated leaves present the image of a plant that is diseased and not fit to eat. It seems to be a plant’s way of putting up a sign to say, “Don’t eat me”. Why else would it compromise its ability to feed itself in demanding, low-light conditions?
Any passing insect or herbivore is searching for an entire, recognisably healthy and tasty leaf. Clever tropical plants trick them into looking elsewhere. It is a tactic that seems to work on shady tropical forest floors. It is not a tactic seen higher in the canopy, suggesting that the dim light on variegated leaves may play a part in the deception. Some herbivores have poor sight. If you can’t be seen, you can’t be eaten.
Archangels are normally considered welcome visitors at Christmas. There are good and fallen angels in the plant world too. If you spot Yellow Archangel with variegated leaves, treat it as an invasive devil. The good Yellow Archangel with entirely green leaves is a welcome sight. In fact, maybe we should revert to appreciating entirely green leaves more?
© Karen Netto (Andrews) 2018-19
Lev-Yadun, Simcha (2014) Defensive masquerade by plants. Biological Journal of the Linnean Society. Volume 113, Issue 4. December 2014. Pages 1162-1166. Published 18 November 2014.