Walnut trees are important food sources for wildlife and humans because they produce large quantities of edible nuts, and they are also valued for fine lumber. They are recognized by very large, alternate compound leaves, chambered pith, and rough bark, and the chemical juglone produced by walnut trees keeps many other plants from growing nearby. Black walnut is highly prized for its rich dark-brown heartwood used for cabinets, veneers, and gunstocks; its bark is used in tanning leather, and a yellow-brown dye can be made from the nut husks, which early colonists also used to dye hair and make stain. The globe-shaped nuts have a strong distinctive taste, and the leaves and nut husks have a citrus scent. Butternut, or white walnut, has lighter wood used for instrument cases and interior finishes, and Native Americans boiled its oblong-shaped sweet nuts to collect oil and make a type of butter, while the sap was boiled down to make syrup. English walnut, the type sold in grocery stores, was brought from the Old World and has smoother light-colored bark and mild-tasting nuts.