Gardeners curse and celebrate the morning glory in the same breath. The common name "morning glory" drives this love/hate relationship -- the confusion comes from the common name spread over a large botanical family. Named for its funnel-shaped flowers that open to greet the rising sun, the morning glory family includes three common varieties: two tropical annuals and one perennial weed. While the garden varieties adapt to many soils, they are fussy about their planting time.
Climbing Morning Glory
Plant annual morning glory vine (Ipomoea tricolor) directly in the garden after danger of spring frost is over. It prefers warm weather. Cooler temperatures delay its growth and, unfortunately, reduce or eliminate the flowers altogether. If you prefer to start this morning glory variety indoors, plant the seeds two to four weeks before your last frost date. It grows rapidly in warm weather, covering trellises, mailboxes and arbors with flowers in shades of purple, pink, white or pale blue.
Dwarf Morning Glory
Plant dwarf morning glory (Convolvulus tricolor) directly in the garden after frost, just as you would vining morning glory. Its roots do not recover well from transplant disturbances. Unlike its cousin, dwarf or bush morning glory remains in one spot rather than wandering over trellises and is suitable for border plantings or foreground groupings. Dwarf morning glory forms a mound up to 16 inches tall and 12 inches wide with flowers in shades of red, blue and white.
Morning glory seeds have tough, hard shells that won't germinate without treatment. In nature, winter freeze-thaw cycles and spring moisture loosen the seed coat. To duplicate this, notch the seed with a knife or, to keep your fingertips safe, rub the seed coat with a file to create a thin area. You can also soak the seeds overnight in warm water. Seeds germinate in four to seven days.
Morning glory is also the common name for field bindweed (Convolvulus arvensis). Not to be mistaken for the tropical annuals that share its common name, this morning glory is a perennial that sends thick, white roots deep into the soil. It is nearly impossible to eradicate and grows quickly enough to overtake your garden in a single season. It regrows from the smallest bit of root and smothers cultivated plants. Use a wide-spectrum herbicide in late summer or fall to kill this weed completely.