Tall Morningglory

What is tall morningglory?

Tall morningglory identification is mostly about the flowers and the hairs: big, showy trumpets in purple, pink, blue or white, plus soft hairs pressed flat on heart-shaped leaves and twining stems. It is the same species sold as common or purple morning glory for fences and trellises, which is how many yards and farms acquired it in the first place.

It becomes a problem because each plant can drop thousands of hard-coated seeds that sprout year after year, and the vines climb over and smother vegetables, shrubs and crops. In farm fields, morningglory vines compete for light and can wrap around crops and harvest equipment. The seeds also carry alkaloids that make them unsafe to eat, which matters around children and pets.

Tall Morningglory identification: what to look for

Check the hairs, the leaf shape and the flowers. Run a finger along a leaf and stem; tall morningglory feels fuzzy, while pitted morningglory is smooth. If you find seedlings, the shape of the seed leaves is a quick giveaway.

• Seed leaves: Green and butterfly-shaped, about 0.6 to 1 inch long and about as wide, so the pair fits neatly inside a square.
• Leaves: Heart-shaped and unlobed, 2 to 5 inches long and nearly as wide, with basal lobes that may overlap slightly. Hairs lie flat on the surface, even on young leaves.
• Stems: Hairy, green to maroon, slightly ridged and twining.
• Flowers: Funnel-shaped, 1 3/4 to 2 3/4 inches long, pale in bud and opening to purple, pink, blue or white, often with a white throat; usually three or more per cluster in the leaf axils.
• Sepals: Narrow and lance-shaped, about 1/2 inch long, clasping the base of the flower instead of curling outward.
• Seeds: Capsules hold 4 to 6 dark brown to black seeds about 1/5 inch across, with two flat sides and one rounded side.

Where it grows in the United States

USDA treats tall morningglory as introduced across the lower 48 states, Hawaii and Puerto Rico. Cornell describes it as established in most of the country, most troublesome in warm, humid regions, and scattered in northern and western states. Because it is still widely grown as an ornamental, you will often find it near old gardens, fences and farmsteads where someone once planted it.

It prefers acid to neutral soils, germinating best around pH 5 to 7 and growing poorly below about pH 5.3, and it needs sun. It cannot flower in shade, so it climbs toward light, which is why it ends up draped over shrubs, corn and fences. Expect it in row crops, gardens, landscape beds and disturbed ground.

Tall Morningglory look-alikes

A few plants get mixed up with it:

• Pitted morningglory (Ipomoea lacunosa): Nearly hairless leaves and stems, a long tapered leaf tip, and small white to pinkish flowers only 0.6 to 1.2 inches long. Its seed leaves split into a narrow V.
• Ivyleaf morningglory (Ipomoea hederacea): Mature leaves are usually three-lobed and covered with upright hairs rather than flat ones. Its bristly sepals curve backward at the tips, and it carries one to three flowers per cluster.
• Field bindweed (Convolvulus arvensis): A perennial that returns from its roots in the same spot every year. Tall morningglory is an annual that dies at frost and comes back only from seed.

How to get rid of tall morningglory

Pulling, digging and mowing: Pull or hoe seedlings as soon as you see the butterfly-shaped seed leaves, and keep cultivating often enough to kill new flushes before they attach to nearby plants. Once a vine has climbed, cut it at the base and let it dry before peeling it away so you don't tear the plant it is wrapped around. On any vine you can't remove yet, pick off flowers and young capsules, since seed matures about four weeks after a flower opens.

Cultural control matters most, because the right conditions keep it from coming back.

• Think twice before planting it near gardens or fields; if you grow it on purpose, remove spent flowers before capsules ripen, because it self-seeds readily.
• Close the canopy: plant crops early and densely so seedlings sit in shade, where tall morningglory cannot flower.
• Do not count on mulch alone; seedlings emerge through thick straw and vines escape through plastic planting holes, so hand-weed mulched beds.

Herbicides: Cornell's turfgrass weed guide lists post-emergence active ingredients for tall morningglory that include dicamba, MCPP, bentazon, quinclorac, halosulfuron and carfentrazone (alone or in combination), plus pre-emergence options pendimethalin and trifluralin; glyphosate is listed as a nonselective treatment for spots with no desirable plants. Post-emergence products go on growing plants, while pre-emergence products must be in place before seeds sprout. Lawn herbicides belong only on lawns and bed or crop herbicides only where their labels allow, so choose a product labeled for your site and for morningglory, and follow it exactly. The label is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Stop the seed. One tall morningglory can produce up to about 26,000 seeds, and hard seed coats keep many of them dormant for years. Pull vines before they flower, and if you keep it as an ornamental, deadhead before capsules ripen.

Be careful with feed grain, manure and hay that might carry seed, and keep fencerows and garden borders clean so vines cannot seed where you are not looking. Working the soil can wake dormant seed, so expect a flush of seedlings after early-summer tillage and hoe them out promptly.

Questions we get about tall morningglory

Similar weeds

Pitted MorninggloryIpomoea lacunosaIvyleaf MorninggloryIpomoea hederaceaField BindweedConvolvulus arvensis