Walnut trees release a chemical called juglone which is toxic to some vegetables and plants, such as tomatoes so it is best to avoid composting anything related to walnuts in case you want to use the resulting compost with susceptible veggies.

The shells from a handful of walnuts isn’t going to cause a huge problem in a big compost heap but if you’re got a lot of shells or nuts to get rid of, it would be better to look for an alternative method of disposal.

Cracking the shells into smaller pieces helps them break down a bit faster and “disappear” into the bulk of the compost – you might not be able to use the compost for sowing small seeds or potting on delicate baby plants, but they’ll be fine in your veg patch or flower beds.

You might be able to reuse or recycle them for something before flinging them in the compost – see Recycle This for creative ways to reuse the shells – such as to aid drainage in plant pots, to make rattle instruments for kids or crafts.