by Vancouver Island Master Gardeners Association
Question: Where can I use chips from a Horse Chestnut tree?
Though most chips are fine for use in the home garden, there are some that should be avoided. Through a unique process called allelopathy, some plants release chemicals through their roots and their leaves that suppress the growth of other plants. This gives the trees a competitive advantage for space and other resources. The horse chestnut is one of these trees, but it is considered only a moderate risk and not likely to affect mature, well-established plants; however, it is better to avoid using them on newly planted beds.
You can age or mature the chips by gathering them in a pile where they will not affect any desirable plants and leaving them to weather for three to four months. This process allows any toxic compounds to break down and renders the chips safe even on newly planted beds.
If you are not comfortable with using the chips in your gardens, you can always use them where you do not want plants to grow.