Rainbow in a Pot: What is variegation?

Why does it happen?

Variegation! Most people know this is a plant that has become a different colour. What is it really, though, and why does it happen?

A plant’s cells may sometimes undergo a random genetic mutation which affects the plastids. Plastids are plant cells that contain chlorophyll, which under normal circumstances would be green. These cells are responsible for creating food for the plant through photosynthesis. 

Instead of creating normal plastids, though, plants sometimes produce defective ones that are colourless. These cannot provide any direct energy value to the plant. The plastids, in some cases, can also be completely absent from a portion of the plant’s tissues. 

The above means variegation is in most situations not beneficial for the plant, as the mutation will cause it to not produce a normal amount of energy. Oddities intrigue us humans, though. A white, yellow, orange or even red plant to show off to our friends can be quite beneficial!

Different types of variegation

Variegation is not something that only occurs in private collections after intense selective breeding, though. It can also appear in nature. Plants may find variegation detrimental in terms of generating energy, as they cannot photosynthesize as they normally would. There are some benefits, though, and straight lines across the leaves are thought to be helpful in repelling pests. Insects may think the plant is sick, and avoid eating it. Many of the variegated forms of houseplants originated from forests, where variegation seemingly occurs more often than normal. It is possible that the low-light conditions of the forest understory play a role in this, but there is currently no adequate explanation for it.

Many species that are currently popular in cultivation have naturally occurring variegation. There tend to be spots on various Adromischus and Aloe species, for example. In addition, a variety of plants like Sansevieria and Euphorbia have lines of variegation running across the body of the plant.

As mentioned above, variegation can occur naturally as spots or lines on a plant. It can also occur as a carefully cultivated and selected-for lack of chlorophyll in certain portions of the plant. The most interesting form of it, though, is “reverse” or “aurea” variegated. This is where the green chlorophyll is completely hidden by defective white plastids. This gives the plant a ghostly white appearance, with vague grey-green lines of chlorophyll hidden deep within the plant tissue. 

Why are they so sought after?

Who doesn’t want to own a rainbow of colours in a pot?

Variegation is popular in cultivation, as many people want to show off something abnormal or unique. This has resulted in the creation of many different selectively bred cultivars and forms, which are readily available in nurseries. Aeonium ‘Sunburst’ is one such plant. It is easy to propagate and grows quickly, and interestingly enough tends to also become crested quite often. Variegated spekboom (Portulacaria afra) and variegated jade tree (Crassula ovata) are also common and easy to grow.

The variegated forms of species such as Haworthia and Aloe, however, tend to grow slowly and are difficult to propagate. They also rarely create offsets that are “true-to-type”, or offsets that are similar to the parent plant. These species also tend to have the most interesting variegated forms. Some have neat lines, and others have a half-and-half split, with one side completely variegated and the other totally green. This combination of a slow growth rate and interesting colouration makes these species highly prized, and incredibly expensive, when in their variegated forms.