Thursday, March 29, 2007

Rhododendron problems

One of the gardens I look after is a woodland garden of about two thirds of an acre, where every plant seems to be about 20 feet tall. It's lovely - but I do seem to find myself doing a lot of pruning!

They've developed a terrible problem with rhododendron bud blast - a fungal disease thought to be spread by a leaf hopper. The leaf hopper is harmless by itself, but lays its eggs by making tiny slits in the buds of rhododendron flowers - which then becomes an entry point for the bud blast fungus.

You can tell bud blast because the buds turn black and look bristly. It's becoming a very common problem - last time I was at RHS Wisley a lot of their rhododendron bushes were affected. Goodness knows how they keep on top of it there.

You can spray against the leaf hoppers, but I've always thought that seemed a bit harsh (and very unfriendly to the environment). The usual treatment is to pick off the affected buds and burn them, but try doing that when the rhododendron bush is twice as high as you are. And you always miss a few, in any case.

I think we'll just have to keep at it and get as many as we can, and hope the problem doesn't do for the rhododendrons altogether. After all, there's not much point in keeping these rather sombre shrubs in your garden if they aren't even going to flower.

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