by Leslie Cox; Wednesday; January 16, 2019

We are entering into pruning season and there are quite a number of shrubs that need attention in our garden…not the least of which is the English laurel hedge, Prunus laurocerasus, in my front garden.

Did you know there is a hidden danger lurking under the bark of this very common shrub? I sure didn’t until very recently.

Catching up on my reading on the days the garden was being thoroughly rain-soaked, I came across a very short article, tucked in the bottom corner of a page in an English gardening magazine. A question in bold print caught my eye.

Are laurel clippings dangerous?

Well, I already knew English laurel (also known as cherry laurel) and Portuguese laurel, Prunus lusitanica, were both poisonous…although they remain very popular as hedging material. What I did not know was the fact they contain cyanogenic glucosides in the leaves.

And here is the potentially dangerous part…when the leaves and young branches are cut, chipped, and/or chewed, the cyanogenic glucosides convert into glucose, benzaldehyde and hydrogen cyanide.

The first two compounds are quite harmless. In fact, because benzaldehyde is aromatic, it is widely used in the perfume industry, pharmaceuticals, and as a flavouring.

However, hydrogen cyanide is another compound altogether. If ingested or inhaled in sufficient quantities, it can be lethal because it blocks oxygen from reaching the central nervous system. (It is also known by its other name, prussic acid.)

There is little danger of poisoning as you prune your laurel hedge. Hydrogen cyanide is easily dispersed when it hits the air…and helped along even more if there is a breeze on pruning day.

But if you like to chip your clippings, burn them, or transport them to the local dump…just be aware of the hidden danger and keep a safe distance. Or be sure to bag the clippings if transporting them in a van or car.

If you smell almonds, you are exposed to hydrogen cyanide. You are now forewarned.