So how do plants that start their lives as normally green-leaved plants suddenly develop white stripes on the leaf margins? Strangely enough, variegation often starts off as one microscopic plant cell getting its genetic information a little mixed up and then growing and multiplying, producing a succession of cells carrying the same misinformation as the original wayward cell. It’s been estimated that something like one in every 500,000 cells produces a mutation spontaneously. Usually the mutation is lethal and the cell simply dies, but rarely the cell survives and replicates, reproducing the mutation right along with its normal characteristics. This is how variegated flowers and foliage come into being.
Not all mutations produce attractive results. The next time you shop in the produce section of your grocery store, have a look at a variety of different fruits and vegetables. If you’re lucky (or, rather, unlucky) you may find a few that look a little strange. I’ve seen navel oranges, for example, that look like half of a smaller orange has been “welded” onto a larger orange half; in other words, a round orange with a thick skin on one half of the sphere and a much thinner skin on the other half. This is the fruit equivalent of variegation on a leaf.
Although it’s rare to find these variegations popping up in your existing, previously non-variegated garden plants, it does happen. (Plant breeders, who propagate millions of plants every year, have a much better chance of discovering spontaneous variegation.) However, even if variegation occurs on your plants, that variegation may not be stable – that is, the new colouration may last only the length of the season in which it originally appears. The following year, the plant may revert back to its original colour, sometimes Canna 'Stuttgart', above, reverts back to an all-green leaf, several shades lighter as well.
Stability of variegated plants has a lot to do with where the variegation itself originated in the plant. Mutations that originated in a specific layer of cells in the growing point have the greatest chance of producing stable offspring for years to come, but if the mutation originated outside of this layer, the chances of that mutation remaining stable are far slimmer.
Not Universally Popular
Of course, some gardeners would be relieved if a spontaneous variegation went away on its own. I find it interesting that a few gardening purists consider variegated plants to be abominations, unworthy of inclusion in the garden because they deviate from the norm, and in the Victorian and Edwardian eras that was the consensus opinion. But in reality, every single species of plant in the world owes its existence to a string of mutations that occurred over the eons. Variegation is just one more variation, and one that I feel makes gardening so rewarding.