Black walnut is a species of tree native to North America, known for its dark, rich wood and edible nuts. The tree can grow up to 100 feet tall and is characterized by its compound leaves and rough, dark bark. The nuts produced by the tree are encased in a green husk that turns brown as it ripens. The wood of the black walnut is highly valued for furniture and cabinetry due to its strength and attractive grain. Additionally, the nuts are a popular food source, often used in baking and cooking. However, the tree's leaves and husks contain a chemical called juglone, which can be toxic to some plants.