Walnut tree wood ashes in the garden

Asked November 4, 2019, 3:57 AM EST

Clearly, there are benefits to adding wood ashes to compost and using it in the garden. I have taken down a dead walnut tree and have lots of walnut firewood. Will the walnut wood ashes, after composting, hurt the plants I will grow in them? Should I avoid putting walnut wood ashes in my compost, and hence in my garden?

Nevada County California

1 Response

Thank you for your question. The answer depends on the interplay between the means by which the ‘poison’ in walnut tissue (juglone) breaks down so as to become ineffective, and whether high heat speeds up this degradation. The phenomenon is described here: https://www.extension.iastate.edu/news/2005/jul/070701.htm So, the composting process itself will reduce or eliminate the effects of juglone on susceptible plants (https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/430/430-021/430-021_pdf.pdf) but only over 6 months or so. I have been unable to find any research specific to the high temperature effect on the chemical. However, you should proceed cautiously before adding any wood ash to your soil—either directly or as a component of compost—according to this Extension article: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16789 Not knowing what your soil pH is, or what you are growing makes it difficult to give you a thumbs up or down, butI hope this is helpful. Good luck!