Camellia Diary 4, July 27, 2010

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The ugly devastation of camellia petal blight

I suspect there has been a bit of a conspiracy of silence about the devastating impact of camellia petal blight in this country. Between camellia enthusiasts, growers and retailers, nobody has really wanted to own up publicly to the fact that it must irrevocably change the types of camellias we plant and they way we use them. The sad thing is that when it was first discovered in Wellington over a decade ago, it was only in two or three locations and if there had been a will, it could probably have been eradicated.

Camellia petal blight at the top, showing the distinctive white ring, merely botrytis on the lower flower

Camellias used to be the second biggest plant seller in this country (roses were number one) and it was the wide use of them in relatively large numbers which aided the spread of petal blight. It is a fungal spore which can travel, apparently, up to 5km on the winds as well as being transferred by infected blooms and soils. The overseas advice to rake up and burn all infected blooms to reduce the spread was simply impractical in a country where they are heavily used in informal hedges and windbreaks. Camellias are seen as utility garden plants in New Zealand and not as show blooms so people were never going to get out with the leaf rake to clear up every single affected bloom.

Botrytis shows up as a darker brown on the bush and has been with us for a long time but nowhere near as devastating as the more recently arrived petal blight.

Botrytis shows up as a darker brown on the bush and has been with us for a long time but nowhere near as devastating as the more recently arrived petal blight.

So petal blight has turned the annual flowering into something of a disappointment, particularly on the japonicas where mass display is a thing of the past. We have always had botrytis here, which can turn blooms to sludge on the bush but the combination of botrytis and petal blight has dramatically reduced the display. Botrytis shows up as darker brown markings whereas petal blight is a paler discolouration. When you turn the blooms over and flick off the calyx (the little hat that holds the petals together on the back), petal blight is revealed as a powdery white ring. Botrytis does not show that white ring. As the affected blooms reach the ground, they give rise to the mushrooms which form at the base of affected plants – these release the spore and the petal blight continues its self contained cycle. Alas the self grooming characteristic (where camellias drop spoiled blooms) so determinedly sought by Les Jury in his days of breeding, no longer apply. Blight means the blooms hang on way past spoiling.

Mark put camellia breeding on the backburner and is only now returning to it as the picture becomes clearer on the directions to pursue. They are still a wonderful and versatile plant but we need to explore different ways to use them in the garden.

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