Plants with variegated leaves are usually found in gardens. But spend enough time in the field, and you might run across some unusual examples in the wild.
In the forest at work, there is a Common Hackberry about ten feet tall, and several limbs have beautiful leaves that are mostly white with green speckles. When I first noticed the tree a few years ago it was a few feet shorter and all the limbs had white leaves. The tree seems to be growing a little bit slower than other hackberries, perhaps handicapped by the diminished amount of chlorophyll fueling its growth. Nonetheless, it is persisting.
In an open area in the same forest, I once found a single Garlic Mustard plant with some very attractive variegated leaves. Garlic Mustard is biennial, so I knew this plant would be back in the coming years. I did check to see if any more came up in the same area after that, but I’ve never encountered another Garlic Mustard plant like the first. Just as well. I would hate to see unsuspecting visitors collecting and planting seeds of non-native and outrageously invasive species.
While sometimes due to a virus, intercell mutation, or “jumping genes”, variegation in plants usually occurs due to a cell mutation in one of the three layers in the plant’s bud, or meristem. If the mutation prevents the normal production of green chlorophyll, the cells arising from that layer will be white, or sometimes yellow or some other color if other leaf pigments show through. Plants with variegated leaves are often known as “chimeras” or “sports.” They are valued in the nursery trade, of course. Finding them in nature is even more invaluable!