Autumn blazing in gardens

There’s been a lot of high pressure over the past few weeks and this has resulted in sunny autumn days followed by quite cold nights, writes Dick Warner.

This kind of weather tends to produce better than usual autumn colour in deciduous trees and shrubs. The Irish climate never manages to produce quite the intensity of colour that they have in the eastern US or Japan, even among American or Japanese species that are planted here, but some autumns are brighter than others and this is shaping up to be a bright one.

Walking through my little wood I noticed something odd. There were two young sycamore trees about 20 metres apart. I planted them on the same day and they are of the same age and provenance but they looked completely different. One was a blaze of pale yellow leaves and the other was a dowdy dark green. They had both experienced exactly the same weather conditions but they had reacted differently to them.

Closer examination revealed that all the leaves on the dowdy tree were covered in black spots about the size of a finger nail. This is sycamore tar spot, a fungal disease that affects all members of the maple family. The other tree was disease-free. The experts say that this disease, which is very common, does the tree no harm, apart from making it a little unsightly. But it seems it must affect the ability to produce autumn colour. As many ornamental maples are grown specifically to provide bright colour at this time of year this makes it a problem.

There’s no cure for sycamore tar spot but you can take preventive measures. The spores of the fungus over-winter on dead leaves on the ground and then reinfect the tree the following spring. If you collect dead leaves at this time of year and burn them there shouldn’t be any spores around next year.

Garden bonfires are illegal nowadays but my information is that you are not breaking the law if you light your fire in a container with a flue or chimney. You can buy (or make) garden incinerators that look a bit like old-fashioned galvanised dustbins with a short flue in the lid.

The smoke that comes out of a short flue is no less polluting than the smoke from an open bonfire so this is all a bit illogical. It’s also possible that different local authorities may have different interpretations of the regulations, so it might be as well to check. But it’s true that there are certain plant pathogens that can not be reliably killed by composting, particularly fungus spores, and we need to be allowed to light an occasional fire.

And I must admit I get nostalgic about garden bonfires in the autumn. This is my favourite season and part of its appeal, for most of my life, was the sight and smell of a gently smouldering pile of garden rubbish.