The VisionarySterling silver walnut on a grosgrain ribbon. The ancient Roman author and naturalist, Pliny the Elder once noted "the shadow of the walnut trees is poison to all plants within its compass" because the fallen leaves and husks of the walnut produce a chemical that oxidizes in soil and impedes other plants ability to grow near them. The truth was actually that the walnut proved poisonous for only certain species of plant and for this reason walnuts