The question of whether a morning glory is a weed or a flower depends entirely on the specific species of plant. Both the beloved garden vine and the aggressive agricultural pest belong to the same botanical family, Convolvulaceae. This family encompasses over 1,600 species, ranging from the sweet potato to various ornamental vines and noxious weeds found globally. The plant’s identity lies in recognizing the difference between the cultivated annuals and the tenacious perennial varieties.
The Dual Identity of Morning Glories
The confusion stems from the common name being applied to two distinct groups of vining plants with similar trumpet-shaped flowers. The desirable plants people cultivate are typically annual species from the genus Ipomoea. These ornamental varieties, such as Ipomoea purpurea or Ipomoea tricolor, are grown for their large, showy blooms in vibrant shades of blue, purple, pink, and white. They complete their life cycle within one growing season and are easy to manage, often used to cover trellises or arbors.
Conversely, the plant classified as a noxious weed is Field Bindweed, Convolvulus arvensis, a different genus within the same family. Field Bindweed is a perennial with an aggressive growth habit, making it a significant problem in yards and agricultural fields. It spreads rapidly and smothers other plants by twining around them and blocking sunlight. Its status as a weed is defined by its perennial nature and deep, persistent root system, which makes it difficult to eradicate.
Distinguishing Invasive Varieties
Identifying whether you have an ornamental or a problematic weed requires inspecting a few physical characteristics. The most reliable visual cue is the shape of the leaf. Ornamental morning glories (Ipomoea) feature soft, heart-shaped leaves that are broad and rounded at the base. In contrast, the invasive Field Bindweed (Convolvulus arvensis) has a distinctly different leaf shape, typically appearing like an arrowhead or a spade with sharp, pointed lobes.
Flower size and color also offer a clear distinction. Cultivated Ipomoea varieties produce large, colorful flowers measuring between two and four inches across. The weedy Bindweed has much smaller, less showy blooms, usually measuring less than one inch in diameter and appearing mostly in white or pale pink. The root system is another important diagnostic feature, visible upon attempted removal. The roots of annual ornamentals are shallow and fibrous, while the rhizomes and taproots of perennial Bindweed are aggressive and can extend nine feet or more into the soil.
Controlling Aggressive Growth
Managing invasive Field Bindweed requires a long-term, multi-pronged strategy focused on exhausting its deep, persistent root system. Simply pulling the visible vines is often counterproductive, as the brittle underground rhizomes easily break apart, and each fragment can sprout a new plant. The most effective mechanical strategy is consistent, repeated cutting of the new top growth at ground level to prevent photosynthesis. This process must be maintained every two weeks for at least a full growing season to slowly starve the extensive underground network of stored energy.
Cultural control methods can suppress the weed by blocking sunlight. Applying thick layers of mulch or using opaque landscape fabric can smother the top growth and prevent emergence. For heavily infested areas, solarization—covering the area with clear plastic sheeting during the hottest months—can heat the soil to temperatures that kill seeds and shallow roots. This technique works best when left in place for several weeks during peak summer.
When infestation is severe, a targeted chemical approach using systemic herbicides is often necessary. Products containing active ingredients like glyphosate or 2,4-D are effective because they are absorbed by the leaves and translocated down into the deep root system. For best results, these herbicides should be applied when the plant is actively growing and flowering, but before it sets seed, to maximize translocation to the roots. Multiple applications over several seasons are generally required to achieve complete eradication.