Last fall, I raked up my fallen cherry tree leaves, and put them in my vegetable garden bed to use as leaf mulch. I don’t know what our cherry tree species is, except that it appears to be ornamental. Then I covered the leaves with burlap coffee bags to winterize the garden bed.
I’ve recently heard that cherry tree foliage and twigs release cyanide when they wilt and decompose. Does this mean that there is cyanide in my garden soil? And if so, will the cyanide be transferred to any vegetables that grow in it? Safe, or unsafe?
A general rule of thumb with fruit trees (in case your cherry is an edible cherry variety) is to gather up fallen leaves under fruiting trees and remove them for good garden hygiene (preventing the spread of disease and any unwanted insects). Provided your cherry is healthy, I don’t think the leaves would pose a serious problem if used as leaf mulch on top of the vegetable garden beds.
The leathery evergreen leaves of English laurel (Prunus laurocerasus, same family as deciduous cherries and plums) are not a good choice for the compost pile because they take a very long time to decompose (which is not the case with deciduous cherry), and they contain cyanide compounds. However, so do apples, plums, almonds, peaches, apricots–all have some cyanide in them.
This link briefly mentions the question of cherry leaves and cyanide in terms of toxicity to animals. Fresh new leaves have a higher concentration of hydrogen cyanide; toxic potential is gone when the leaves turn brown. True enough, this is about eating the leaves, not letting them sit on the soil, but I imagine the concentration would be very low, and there are all sorts of things in our soil that in small doses are not likely to cause harm, and may or may not even be taken up into the roots of anything you plant there.
I asked Washington State University Extension Horticulture professor Linda Chalker-Scott what she thought about the safety of using those leaves and twigs on your vegetable bed, and she said, “Cyanide does not persist in soils. It is HCN [Hydrogen cyanide], which is quickly broken down by microbes in search of nitrogen. It is really nothing to worry about.”