With spectacular trumpet-shaped flowers up to 6 inches in diameter, morning glories (Ipomoea spp.) are most frequently grown as annuals, though they can be perennial in U.S. Department of Agriculture plant hardiness zones ranging from 8 to 12. Their heart- or ivy-shaped 4 to 6-inch leaves decorate twining vines which can climb to 20 feet or more. Morning glory blooms usually close by noon on sunny days, but frequently will remain open longer on overcast ones. Easy to grow, the plants can become invasive in almost any climate due to their heavy self-seeding.