Variegation is the appearance of differently coloured zones in the Leaf, Flower, and sometimes the Plant stem and fruit of Plant, granting a speckled, striped, or patchy appearance. The colors of the patches themselves vary from a slightly lighter shade of the natural coloration to yellow, to white, or other colors entirely such as red and pink.
Many species which are normally non-variegated are known to display variegation. Their appearance is desirable to enthusiasts, and many such plants are propagated and sold as unique Cultivar.
The term is also sometimes used to refer to colour zonation in Mineral and the integument of Animal.
Causes
Chimeral
Chimeric plants contain tissues with more than one
genotype. A variegated chimera contains some tissues that produce chlorophyll and other tissues which do not.
Because the variegation is due to the presence of two kinds of plant tissue, propagating the plant must be by a vegetative method of propagation that preserves both types of tissue in relation to each other. Typically, stem cuttings, bud and stem
grafting, and other propagation methods that results in growth from leaf axil buds will preserve variegation. Cuttings with complete variegation may be difficult, if not impossible, to propagate. Root cuttings will not usually preserve variegation, since the new stem tissue is derived from a particular tissue type within the root.
Structural
Some variegation is caused by structural color, not pigment; the microscopic structure of the plant itself reflects light to produce varying colors. This can happen when an air layer is located just under the epidermis resulting in a white or silvery reflection.
It is sometimes called blister variegation.
Pilea cadierei (aluminum plant) shows this effect. Leaves of most
Cyclamen species show such patterned variegation, varying between plants, but consistent within each plant.
The presence of hairs on leaves, which may be coloured differently from the leaf itself, can also produce variable coloration. This is found in various Begonia species and their hybrids.
Sometimes venal variegation occurs – the veins of the leaf are picked out in white or yellow. This is due to lack of green tissue above the veins. It can be seen in some Araceae. The Silybum marianum, Silybum marianum, is a plant in which another type of venal variegation occurs, but in this case it is due to a blister variegation occurring along the veins.
Pigmentary
A common cause of variegation is the masking of green
pigment by other pigments, such as
. This often extends to the whole leaf, causing it to be reddish or purplish. On some plants however, consistent zonal markings occur; such as on some clovers,
Bromeliaceae, certain
Pelargonium and
Oxalis species. On others, such as the commonly grown forms of Coleus, the variegation can vary widely within a population. In
Nymphaea lotus, the tiger lotus, leaf variegations appear under intense illumination.
Pathological
Virus infections may cause patterning to appear on the leaf surface. The patterning is often characteristic of the infection. Examples are the
mosaic viruses, which produce a mosaic-type effect on the leaf surface or the citrus variegation virus (CVV). Recently a virus disease,
Hosta virus X (HVX) has been identified that causes mottled leaf coloring in
hostas. At first, diseased plants were propagated and grown for their mottled foliage, at the risk of infecting other healthy hostas.
While these diseases are usually serious enough that the gardener would not grow affected plants, there are a few affected plants that can survive indefinitely, and are attractive enough to be grown for ornament; e.g. some variegated
Abutilon varieties.
Nutrient deficiency symptoms may cause a temporary or variable yellowing in specific zones on the leaf.
Iron and
magnesium deficiencies are common causes of this. Transposable elements can cause colour variegation.
Defensive masquerade
It has been suggested that some patterns of leaf variegation may be part of a "defensive masquerade strategy."
In this, leaf variegation may appear to a
leaf miner that the leaf is already infested, and this may reduce parasitization of the leaf by leaf miners.
Nomenclature
By convention, the italicised term
'variegata' as the second part of the Latin binomial name, indicates a
species found in the wild with variegation (
Aloe variegata). The much more common, non-italicised, inclusion of 'Variegata' as the third element of a name indicates a variegated
cultivar of an unvariegated parent (
Aucuba japonica 'Variegata'). However, not all variegated plants have this Latin tag, for instance many cultivars of
Pelargonium have some zonal variegation in their leaves. Other types of variegation may be indicated, e.g.
Daphne odora 'Aureomarginata' has yellow edging on its leaves.
Usage
Variegated plants have long been valued by gardeners, as the usually lighter-coloured variegation can give texture or variety to what would otherwise be blocks of solid green foliage. Many gardening societies have specialist variegated plants groups, such as the Hardy Plant Society's Variegated Plant Special Interest Group in the UK.
In 2020, a variegated Rhaphidophora tetrasperma plant sold at auction for US$5,300.
See also
-
Glossary of botanical terms
External links
