Japanese gardens (日本庭園, nihon teien) are traditional gardens whose designs are accompanied by Japanese aesthetics and philosophical ideas, avoid artificial ornamentation, and highlight the natural landscape. Plants and worn, aged materials are generally used by Japanese garden designers to suggest a natural landscape, and to express the fragility of existence as well as time's unstoppable advance. Ancient Japanese art inspired past garden designers. Water is an important feature of many gardens, as are rocks and often gravel. Despite there being many attractive Japanese flowering plants, herbacious flowers generally play much less of a role in Japanese gardens than in the West, though seasonally flowering shrubs and trees are important, all the more dramatic because of the contrast with the usual predominant green. Evergreen plants are "the bones of the garden" in Japan. Though a natural-seeming appearance is the aim, Japanese gardeners often shape their plants, including trees, with great rigour.