Science lesson: variegation

by Caroline Brown

Variegation is when plant foliage, stems, or flowers have more than one color. It’s most often found in leaves. The most common leaf variegation colors are white, cream and yellow, but there are many others, including pinks and purples.

Cats can also be variegated, but I’ll leave that phenomena for the pet bloggers to explain.

Most plants with variegated foliage are chimeras. Chimeras have a gene that causes some areas of their leaves to have less–or in some cases, completely lack–chlorophyll, the green pigment in plants. In chimeras, the gene causes the cells in the variegated area to lose their ability to produce chloroplasts, which is where chlorophyll molecules are housed.

In some some non-variegated plants, chlorophyll is completely masked by the pigment anthocyanin, which is responsible for reds, purples, and blues. Anthocyanin brings us foliage with dark reds, purples and pinks–think of all the Japanese maple (Acer palmatum) hybrids with dark purplish-red leaves. Anthocyanin is one of the pigments that’s often left behind in the fall when chlorophyll fades, giving trees such as the red maple (Acer rubrum) their name. Add excess anthocyanin to a chimera and that brings us all sorts of variegated combinations; think of tri-color beech, coleus, or the endless variations of the heuchera.

Gardeners value variegated plants for their ornamental beauty. Plantsmen know this and are more than happy to provide us with our fix of plants that are specifically cultivated for variegated foliage. But because not all parts of the plant can photosynthesize, some variegated plants are not as robust as a “normal” green plant. Variegated plants are rarely seen in the wild for this reason (survival of the fittest and all that.)

Want to propagate one of your favorite variegated plants? Both the green and the “non-green” plant tissues have to be present. Stem cuttings or bud and stem grafting usually work better than root cuttings. Variegation is not always a “stable” trait, meaning the plant or its progeny can “revert” back to the all-green. I often see plants described as losing their variegation if they aren’t given the proper amount of light…both too much or too little sunlight can be a culprit, depending on the plant.

At left is a pruned branch from a tri-color beech. It’s not a great photo but you can see how the white, pink and green variegated leaves on the bottom part of the stem have given way to much larger, green-only leaves towards the top. This is an example of a branch that is reverting back to the all-green version. I don’t know exactly why this particular branch reverted (none of the others did), but it was extremely unattractive and had to go.

My favorite variegated plants are heucheras (coral bells). Several varieties, such as ‘Velvet Night,’ ‘Plum Pudding,’ and ‘Prince of Silver,’ are beautifully dimensional with variegations of dark green, purple, and silver. To me, variegated plants look best in the shade garden, because shade can make green look pretty dark and monochromatic. In the shade garden , variegated leaves are like little splashes of sunlight.

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8 Comments to “Science lesson: variegation”

  1. I like this photo a lot.

    Variegated leaves add such beauty to so many plants, especially the deep reds and pinks, with the beautiful velvety leaves (have no idea what plants these were, but so pretty).

    Variegated coats on felines are even better!!! 😉

  2. This was a great explanation for variegation of foliage – something I’ve always wondered about. As I was reading this, I looked at the Hoya. The variegation is very uneven. There are some totally green leaves near the bottom with some almost totally cream-coloured leaves near the top. Interesting to see an example of what you are talking about without even leaving my chair!!

  3. Very well written explanation, thanks! I love the photo with the cat! Excellent!

  4. I’m really glad I read this. I’m trying to propagate a “Dark Heart” coleus I love, but that’s really getting aged and leggy. He’s actually throwing out seed (huh, did someone say porn?), so I’m trying to grow it. Anyway, now I know why that plant is the color it is.

  5. Gee, now I know! Thanks. I do love variegated plants. I think it just might just be mandatory to have a variegated cat to go with them. I’ll have to look that up.

  6. Dear Caroline – I now have a better understanding of variegation in my acers but I dont know how to correct some branches and later maybe the tree from reverting to plain green. Is there anything Ican do other than remove the offending branches ? Can I feed itwith anything to help?Apreciate a response -many thanks Roger.

  7. Hi Roger, it’s my understanding that the best way to get rid of the reversion is to prune the branches. However if this means you’ll be pruning so much of the tree that you will “maim” it, maybe you should just consider leaving it. (no pun intended). I guess a green tree or part-green tree is better than an ugly maimed one!

  8. Just a quick note on this though may be too late. Roger if your Acer’s are reverting and they are Norway Maple, I wouldn’t leave it, I’d cut down the tree. They commonly revert and the common species can set seed and become horribly invasive. I have first-hand experience with this. Norway maples really need to be stopped.

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