Tim EntwisleVariegation – streaky, blotchy and generally unattractive

I hate variegated plants. There, it’s out. To me they look sickly, a little phoney and in most cases simply unattractive. It’s the washed out yellow colour I dislike particularly. Reds I can stomach, sometimes. Although we tend to blame variegation on viruses, mostly it’s bad genes. For example the streaked leaves of shell ginger (Alpinia zurumbet), and presumably the single leaf of the Oyster Plant (Acanthus mollis) I’ve photographed here, are caused by cells within the plant mutating so that the production of the green pigment, chlorophyll, is stopped.

Acanthus mollis variegated leaf

Acanthus mollis variegated leaf

 

If these yellow cells are in what is called the meristematic area – where new tissues are produced – a streak or blotch ensues. Meanwhile neighbouring cells retain the original genetic makeup and keep producing green and more productive tissue.

variegated coleus

Variegated subtropical plants

 

Red coloured blotches are caused by an overproduction of anthocyanin, in this case masking the green of the chlorophyll. (The same thing happens in autumn leaves – yellow leaves are yellow because the chlorophyll has been withdrawn, red leaves are red because anthocyanin has been added.) The actual patterning of the variegation depends on where in the meristem the mutant cells arise.

plant variegated

Variegated gold dust plant, Aucuba japonica

 

Genetic mutations occur often and throughout a plant. We don’t notice most of them because they are either in a non-meristematic area (so no or few new cells result with the mutation) or the mutation is not particularly obvious (e.g. it might result in more sugar being produced or a thinner cell wall).

Similarly I presume with viral infections – i.e. some are more obvious in their symptoms than others (and of course many a serious impact on agricultural crops). These days we can usually identify the virus responsible for a disease or a discolouring. For example the Bengal Tiger and Pretoria cultivars of Canna have been shown to be due to a Yellow Mottle Virus. And the stunted forms of Sacred Bamboo (Nandina domestica) with red, curled leaves are due to a virus called the Nandina Stem Pitting Virus.

Variegated mutation on Acanthus

 

In plants such as Sacred Bamboo it’s not known how the virus gets from one individual to another but normally it is through sap-sucking insects or a piece of the plant itself. Where a virus-induced variegated plant is widely available in horticulture it is usually propagated by cutting or graft.

By the way, viruses are tiny packets of genetic material inside a protein protective case, too small to be seen in a normal optical microscope. They can only reproduce inside the cell of a living organism, although there is a ongoing debate about whether to call a virus living or non-living (or indeed whether the word ‘life’ is useful at all when there is a continuum of life-like chemical reactions on Earth).

There can also be some uncertainty about whether variegation in some species is caused by a random mutation or the arrival of a colour inducing virus. Although Tulip Breaking Virus was encouraged in 17th century Holland during ‘Tulipmania’, these days bulbs producing streaky flowers and sold under the name Rembrandt Tulips are generally free of viruses (or at least of viruses causing floral streaking).

white variegated osmanthus

White variegated Osmanthus

Variegated hibiscus

Variegated hibiscus flower

 

I think its fair to say that in most cases variegation is caused by mutated genes rather than viruses. No matter what the cause, plants with variegated leaves will be out competed by fully green plants because the yellow plant tissue doesn’t have the chlorophyll required to trap the sun’s energy and turn carbon dioxide and water into the sugars required for growth. And variegated flowers are likely to be less attractive to pollinating the insects and animals that have evolved an attraction for a particular floral display. So you would expect to find few variegated plants in nature.

In (some) gardens, though, variegated plants thrive. They have seduced (some of) us into helping them survive and prosper. While I may not love them, I can turn a blind eye to a leaf or two.

[Thanks to Dan Murphy, a colleague at the Royal Botanic Gardens, for suggesting this topic.]

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Tim Entwisle

About Tim Entwisle

Dr Tim Entwisle is a scientist and scientific communicator with a broad interest in plants, science and gardens, and Director & Chief Executive of Royal Botanic Gardens Victoria. Previously he was Director of Conservation, Living Collections & Estates at Royal Botanic Gardens Kew and prior to that, Director of Sydney’s Royal Botanic Gardens for eight years. Read Tim's full blog at Talking Plants

8 thoughts on “Variegation – streaky, blotchy and generally unattractive

  1. Hi Tim (and Dan),

    Here comes a reply from a lover of variegated plants. Please come and see my collection and I’ll soon change your mind. I’m loving my striped grasses, my variegated Iris, totally adore Hydrangea macrophylla ‘Quadricolor’. Need and cosset the variegated land cress – one of the best. Have just had a query re a variegated Abutilon from S. Australia – we’re out there Tim. Please send all unwanted, rare preferably, plants to me at Bilpin. I believe that the Japanese nurserymen are adept at developing beautiful variegates. Give me my head and a book is there in the making. (I have been accused of maybe having a variegated brain by another keen plantsman). Love the fact that we all like something different.
    PS Angus Stewart once described one of my gardens as, “a bed of excitement”. Apparently too many variegated plants close to each other can cause this affliction!!
    Yours, Peta Trahar

  2. Excellent! As long as you have passion for plants I forgive you… Actually I have a few friends who have said that I should allow monocots to be variegated, as they do it quite well. Your garden does sound wonderful and I have not doubt I could be trained to get over my variegation phobia. I can’t remember if there is much variegation going on in my previous garden at Mount Tomah but I don’t think so. Or have I forgotten? Great to hear about your garden and your enthusiasm for these genetic and viral variants. Tim

    • And a PS. At the recent and inspiring Landscape Conference in Melbourne (great excuse to fly south), Ken Smith from New York arranged the big pots of variegated Beschorneria so that they resembled a cross between giant sea urchins and a sort of Dr Who army stalking each of the speakers. I loved them. Am pleased at the thought of converting you……Peta

  3. Robert Chin on said:

    Hi Tim. If your going to come out – then I am as well – thanks for having the courage to say this. I too think that plants that are variegated are just genetic mutants lacking the vigour of their uniformly coloured ancestors. But how far do we go? Is Cauliflower a mutant Broccoli without the chlorophyll? Like you I fear that this puts us in the minority. BUT – I work in the Nursery Industry and even though I don’t like them – the good ones do sell like the blazes so I would never say this publically or tell my wife who just loves them.
    A great column on a great website.

  4. dirtgirl on said:

    Gosh – I am with Peta – I adore variegated plants and will go out of my way to obtain them. I never realised folks didn’t even like the poor things until recently when a friend asked for some of the Nasturtium seeds from my garden, but then added – ‘Please don’t give me any variegated ones, I hate them’ Thank goodness we are all so different in our own ways, otherwise our gardens would all look the same…..

  5. I like the fact we can passionately love or hate, in this case, variegated plants. Better to be reacting in some way, and arguing the merits, rather than seeing all as green wallpaper. Tim

  6. Paul Plant on said:

    Well you can guarantee a response with that attention-grabbing title.
    Variegated plants are essential for garden designers, plant collectors and admirers of biodiversity as the offer us relief from the mundane catatonic proliferation of boring plain-leaved plants.
    Ahhh – that feels better 🙂

  7. Hi Paul,
    Don’t worry, I have no higher aesthetic judgement or perception – as you already know! It’s a funny personal thing. I know some people love them, and as you say they provide solutions to a wall of green. I personally try to avoid them and would favour other shades of green and other structural (leaf) elements, from among those charmingly elegant non-variegated plants. I have to confess I do have a wee soft spot for red foliage in the right place – the tropics/subtropics… Tim

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