At this time of year I don't usually recommend the burning of leaves. Indeed I have to say that one of the most important things you do in any garden is to build a leaf pit. As described last year, there are a few ways of doing this, from buying the string bags, to using old pallets and corralling the leaves for a year of gentle rotting. Then, when all is going to sleep next year, you can use the leaf-mould as a vital mulch.
However, with the rise of leaf borne pathogens in specific trees and plants, I would recommend you collect and burn as many leaves as possible. The two trees which are most important in this respect are the Aesculus hippocastanum (Horse-chestnut) and Fraxinus excelsior (Common Ash).
At present we are looking at the destruction of between 50% and 90% of these trees in our fair country. Some of you may have noticed over the past few years that the Horse-chestnuts have browned very early in the year. This is due to an invasive leaf miner moth (originally from Serbia, Cameraria ohridella), which lays its eggs on the leaf and the caterpillar eats its way through the leaf. These leaves fall to the floor and the caterpillar overwinters in the leaf litter. It must be said here, that the moth does not kill the tree. But it does weaken it enough for a fungus to attack the tree itself and kill it. Thus collect up all leaves of the Horse-chestnut and burn them. The moth is not native and should not be here. For more information visit http://www.forestry.gov.uk/fr/INFD-68JJRC
The second tree under threat of a leaf borne pathogen is the Ash tree. Approximately 80 million trees are under threat of destruction from the fungus Chalara fraxinea. With the same care and attention, if you have one of these beautiful trees in the garden, again collect up all the leaves and burn them. For more information visit http://www.forestry.gov.uk/chalara. Whilst it is admitted both these diseases are now established in the UK, perhaps we can, with care, prevent them from destroying our valuable woodlands.
For a handy hint on how to identify the horrible Ash Dieback disease watch this Youtube video.
-- Guy Deakins