Morningglories are a family of annual weed known for their vining characteristics and their trumpet-shaped flowers. Their vining nature can be injurous to surrounding plants, and they are best controlled at the seedling stage. They prefer moist soils.
Morningglory seedlings usually germinate during favorable moisture conditions. The cotyledons are butterfly-shaped with tips having two lobes. Seed leaves are hairless, partially glossy, and dotted with glands on the upper side. Unlike other morningglory species, the cotyledons are mostly squarish. The first true leaf is heart-shaped and generally hairless, while the subsequent leaves keep the shape and add hairs.
The mature leaves of the morningglory grow alternate and have small, evenly distributed hairs that lie flat. They grow 3 to 5 inches long and maintain the heart shape throughout the life of the plant, with the older leaves sometimes having lobes that overlap at the base. Some leaves are three-lobed. The stem of the morningglory is a vine that branches, twines, and climbs up surrounding plants. Tall morningglory plants can reach 6.5 feet in length. They are distinct from other morningglory species because of the heart-shaped leaves.
Tall morningglory flowers bloom from June to November. Colors can be red, blue, violet, white, and pink, with some being multi-colored. They grow in singles or clusters of 2 to 5 and are funnel-shaped, stalked, and overall quite showy. Flowers grow up to 3 inches long.
Tall morningglory plants are very aggressive and can quickly become problematic to farmers if they are not destroyed as seedlings. Being vines, they by nature climb neighboring plants and compete heavily for sunlight. having 2 morningglory weeds per square foot can reduce yields in soybeans by 40 percent. The tough stems can also become tangled in combine heads. Once a vining tall morningglory has established itself, it will be extremely difficult to control without damaging the crop. Seeds contain alkaloid compounds which are toxic to humans and animals when consumed.
There are not many options for mechanical control of tall morningglories. Typical practices for weed control such as tillage and crop rotation may prove effective. A cover crop will potentially exacerbate the problem.
In corn, tall morningglory is best controlled with a combination of preemergence and postemergence herbicide programs. In corn and soybeans both, a postemergence application of glyphosate will control or suppress tall morningglory. Be aware that many morningglories are not particularly sensitive to glyphosate. Some active ingredients in contact herbicides that are effective include fomesafen, lactofen, and acifluorfen. These must be applied early on in the plant's life for maximum effect. Please contact your local weed specialist to learn what is most effective in your area and how to use it best. Always read and follow all label instructions.