A variegated leaf or stem has sectors, patches or stripes with two or more different colours, even distinct shades of green. Plants with variegated leaves are often highly prized.


Left: a variegated Cereus sp. forma mostruosa cristata

Right: a variegated Haworthia attenuata

 

Some variegations are attractive and ornamental, and many of them  has been preserved and widely cultivated.
Variegation may be due to a number of causes.

• Chimeral variegation In most plant species leaves or stems are normally green, and variegated leaves are an uncommon mutation, termed a chimera.  A chimeral variegation is due to losing the ability to produce chlorophyll in some of the plant’s tissue, so that this tissue is no longer green. Tissues lacking of chlorophyll are usually white or pale yellow coloured (due to carotenoid pigments) contrasting with the normal green tissue. There are several forms of such variegation, depending on the tissues that have been affected. The variegation in some forms is unstable. The extent and nature of the variegation can vary, and sometimes the plant will return to the green form. In others it is stable and does not change under normal conditions. 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. As these plants have some of their tissue unable to carry out photosynthesis (albinos), the plant will be weaker than the plain green plant. They should generally be expected to die out in the wild.

• Variegation due to reflective effects Some variegation is due to visual effects due to reflection of light from the leaf surface. 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. Cyclamen hederifolium leaves show such patterned variegation, varying between plants, but consistent within each plant. Another type of reflective variegation is caused by hairs on parts of the leaf, which may be coloured differently from the leaf. This is found in various species and garden hybrids.

• Venal variegation  the veins of the leaf are picked out in white or yellow. This is due to lack of green tissue above the veins. it is due to a blister variegation occurring along the veins.

• Variegation caused by other pigments A different cause of variegation is the camouflage of green pigment by other pigments, such as anthocyanins or betalain. This frequently expands to the entire leaf, whit reddish or purplish patterns. On some plants however, consistent zonal markings occur such as the common Coleus, the variegation can be very different inside a population.

• Pathological variegation Virus infections may origin variegation to appear on the leaf or stem surface. The feature is often characteristic of the infection. Examples are the mosaic viruses produce a mosaic type. Although these infections are generally grave enough to affected plants, there are a few infected plants that are grown for ornament;

• Nutrient variegation Deficiency symptoms may cause a temporary or variable yellowing in specific zones on the leaf. Iron and magnesium deficiencies make the leaf veins remain green and the areas between the veins turn yellow.