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Convolvulus is a genus of flowering plants composed of about 250 species. Convolvulus species can be upright, crawling, or climbing plants, and either annuals or perennials. The genus name, which means "wound together," is reflective of some species' habit of binding themselves to other plants or landscape features. Genus members with solitary flowers include the ornamental morning glory, C. tricolor, and the invasive field bindweed, C. arvensis. C. cneorum, sometimes called silverbush, is a perennial shrub evergreen cultivated for its flower clusters.
Species of the Convolvulus genus occur widely in subtropical and temperate climates around the world. The flowers of most trailing species are usually about an inch (2.5 cm) wide, and come in a variety of colors, including white, pink, and violet. Most Convolvulus species prefer poor to average, well-drained soil, as well as full sun and moderate watering. Due to their less demanding soil requirements, they are often grown in rock gardens. Most cultivated species also grow well in containers or hanging baskets, which can be desirable if the species has a tendency to spread.
Perhaps the most popularly cultivated Convolvulus species is C. tricolor. This plant is often called a morning glory, but that name is also shared with other Convolvulus species, as well as some species of other genera. C. tricolor is usually cultivated as a bushy annual that grows about 12 inches (30 cm) tall and produces 1 1/2 inch (4 cm) flowers. Its three-colored flowers have a yellow center, white middle ring, and violet or purple outer ring. The flowers last only a day, but new flowers appear in great numbers throughout the summer.
Sometimes called bush morning glory or silverbush, C. cneorum is an evergreen shrub with silky, silver leaves. It bears flowers similar to those of C. tricolor, that are mostly white with a yellow center. The flowers grow in clusters of about five. When grown in a container, C. cneorum can be brought indoors during cold winters. Other cultivated species include C. althaeoides, C. sabatius, and C. boissieri, all of which are trailing or creeping perennials.
Some Convolvulus species produce running or spreading roots and can quickly become invasive. Field bindweed, C. arvensis, is one example, and while not usually found in gardens it can be damaging to agricultural crops. The running roots of bindweed, which spread underground, can be up to 20 feet (6.1 m) long. The flowers are similar in shape to those of C. tricolor, but are usually white with a pinkish hue.