I have a few of the non-invasive species of Cotoneaster and last week I gave one of them a good pruning to clear some ground. The cuttings sat around for a while in the heat (it’s been hot all summer) and then got rained on a couple of days ago. Then I decided to shred them. Mmmm, what a delicious and really quite strong smell of almonds from those bruised and shredded stems and leaves…yum…hang on…my Agatha Christie knowledge tells me that could be cyanide…
A quick search later reveals that Cotoneaster contain cyanogenic glycosides (see e.g. The Poison Diaries). That means chemicals in the plant that can produce cyanide. Usually these are at low concentrations and toxic effects only occur if large amounts are eaten (such as by an unfortunate llama reported in a veterinary journal (Grüss & Priymenko, 2009)). Of the leaves, bark or fruit of some species, the leaves have been found to have the greatest concentration (Tidwell et al., 1970). However after all that sun we’ve had, my herbs are very tasty at the moment – maybe the Cotoneaster has more cyanogenic glycosides than usual, that have started converting to cyanide in the damp of their waste heap? I stopped sniffing and stopped shredding and washed my hands, but the compost heap where I’d put some shredded material might take a little while to recover.
References
Grüss, Aurelie & Priymenko, Nathalie (2009) Cotoneaster sp. poisoning in a llama (Lama glama) Journal of Veterinary Diagnostic Investigation 21, 247-249. Retrieved from SagePub.com on 17Aug2018
Robert H. Tidwell, Beal, J., Dhanooprasad G. Patel, Tye, A., & Patil, P. (1970). A Study of the Cyanogenetic Content and Toxicity of the Fruit of Selected Species of Cotoneaster. Economic Botany 24(1), 47-50. Retrieved from http://www.jstor.org/stable/4253108 on 17Aug2018
Limestone Garden 