Walnut

What shall I do with fallen walnut leaves?

Garden Experts

As my walnuts were once again almost completely back this year, I'm attempting to gather as many nuts and shell remains as possible.

What should I do with the leaves? The first leaves that fell earlier than usual were all spotted and looked very unwell. Is it worth gathering as many of these leaves as possible and destroying them, as you would with chestnut leaves? Or can I leave the foliage lying on the soil as usual? Alternatively, can I compost some of them?

The GARDENA Garden Expert answers

You are correct — fungal infections in walnut shells and leaves mean that you have to consider what is the best way to proceed with infectious garden waste such as this. Leaving them to lie and rot is not the solution, as this will allow the fungal spores to terrorise your walnut tree even more. The spores are essentially everywhere, even on the bark of the tree, but disposing of the waste will at least minimise future infestation.

Composting the waste probably won't achieve anything, as you have to be able to ensure that the composting will take place under heat, at a decomposition temperature that will kill the pathogens reliably. The only way to reliably achieve this is by dedicating special attention to the issue and composting in the proper manner. Achievable in principle, but takes a great deal of effort.

Therefore it seems to me that the most feasible option is gathering the waste and taking it to a bio-waste recycling facility, where it can then undergo professional hot composting.

Quite pragmatically, I have resolved the problem in similar scenarios like so: Dig a pit in an inconspicuous corner of your garden, approximately three cuts of a shovel deep and sufficiently large, throw in the necessary waste and then cover it all in earth again. If you want a perfect result, place the rotting material in the pit in layers and sprinkle each layer with quicklime to disinfect it. Be careful when handling quicklime, as it is extremely alkaline.

This procedure will initially result in something resembling a burial mound—hence why you should choose an inconspicuous corner of your garden—but this will diminish again in a few months. If necessary, you can hide the mound by planting courgettes or similar in the spring. The important thing is that you dig the pit deep enough so that the rotting material (if left untreated with quicklime) doesn't make its way back to the surface when you next dig up the earth.

In addition, you can apply 70 grams of quicklime per square metre (roughly equivalent to three tablespoons) to the soil underneath the walnut tree itself in order to disinfect the earth. It is best if you do this shortly before a rain shower.