Plant Doctor Archive

Ailing camellias

THREE years ago 27 sasanqua camellias were planted as a hedge in my garden and they flourished until last year. Now, most of them have symptoms such as swollen black veins and leaves that have become hard to the touch rather than being soft and supple. The whole hedge has lost its vigour.

I CHECKED with camellia expert Neville Hayden who confirmed my opinion that your camellias almost certainly have a root problem. Neville calls these symptoms "leaf scab" or "corky excrescence". The most likely cause is root disease caused by waterlogged soil in winter, excessive drought in summer or a combination of the two. The failing root system is incapable of conducting water from the soil to the leaves, causing the leaf symptoms and the obvious lack of healthy buds and no new growth.

If the soil does get excessively wet in winter you need to try to improve drainage. I suggest you first try digging a drain about 50cm or so out from the hedge along the whole length of one side. Dig the trench as wide as your spade and about 30cm or so deep and make sure one end leads downhill so any water that collects in the drain can flow away. I'd leave it as an open trench for several months until it's obviously working well, then you could fill it with coarse gravel or scoria.

Alternatively, if you feel summer drought is more likely the cause, you could consider installing an irrigation system. There are simple kits available at most garden centres and hardware stores. Or spread a 10cm layer of bark or compost mulch over the soil beneath the hedge to help retain moisture and water deeply with a hose once or twice a week during dry periods. Once it gets well established, a sasanqua hedge should be capable of withstanding most summer conditions without extra watering.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.