allelopathic

i am working with the United State Botanical Garden in Washington DC on a commission for a large shadowbox display on the black walnut tree. in preparation for that, i cut these tree circles to use in the display. can you believe how gorgeous black walnut wood is? the dark centers are called the heartwood, and the light outer circles are called the sapwood. black walnut trees are allelopathic, meaning they excrete chemicals into their environment that harm competition. records of walnut toxicity to other plants have been observed as far back as the first century when Pliny the Elder wrote: “The shadow of walnut trees is poison to all plants within its compass.”

eastern American black walnut tree circles (Juglans nigra)