Fruit trees would sometimes line paths, to provide shade and produce, but fruit bushes were as common as fruit trees and always planted in the interior of the garden. Fruit trees would also be planted along the external border of the garden (while wealthier people with more land planted them in orchards). Ornamental shrubs were rare, but could include azalea, lilac, and mock orange. A stand-alone herb garden was uncommon in the United States. However, Colonial American herb gardens were generally of the same design as other gardens. They were usually less than across, and often consisted of four square plots separated by gravel paths. More commonly, herbs were mixed in with flowers and other plants. Commonly planted herbs included angelica, basil, burnet, calendula, caraway, chamomile, chervil, coriander, comfrey, dill, fennel, licorice, mint, nasturtium, parsley, sage, and tarragon. Herbs to a Colonial American did not have the same meaning as the words does in modern America. To colonists, "herb" meant not only savory plants added to dishes to enhance flavor but included medicinal plants as well as greens (such as nasturtiums and calendulas) meant to be eaten raw or cooked as part of a salad. The Colonial Revival gardening movement traces its origins to the Centennial International Exhibition of 1876, the first official World's Fair held in the United States. The Centennial Exposition was held in Philadelphia, Pennsylvania, from May 10 to November 10, 1876, and it celebrated the 100th anniversary of the signing of the Declaration of Independence. Although the Colonial Revival gardening movement had already begun a short time before, the Centennial Exposition created intense interest in all things colonial — including the colonial garden. Colonial Revival gardens were widely popular from the late 1800s to the late 1930s. The Colonial Revival gardening movement occurred primarily in the eastern United States (where colonial heritage was strongest), although the gardens were constructed across the country. A number of writers published highly influential books about the Colonial Revival garden. Among these were  Alice Morse Earle's "Old Time Gardens" (1901), Alice Morse Earle's "Sun Dials and Roses of Yesterday" (1902), and Grace Tabor's "Old-Fashioned Gardening" (1913). Colonial Revival gardens do not seek to imitate or replicate actual colonial gardens or colonial planting schemes.