The classification of morning glory as a weed depends entirely on the specific species. The common name applies to numerous climbing plants, some cherished for their vibrant, trumpet-shaped blooms. However, the term also describes one of the most stubborn and reviled agricultural weeds worldwide. This dual identity is the source of frequent confusion for gardeners managing the plant in their landscapes.
The Botanical Identity of Morning Glory
All plants known as morning glory belong to the Convolvulaceae family, often called the bindweed family. Members share the characteristic of having funnel-shaped flowers and a twining, vining growth habit. A major distinction exists between the ornamental types and the problematic weeds, primarily concerning their genus and life cycle.
Desirable ornamental varieties are typically Ipomoea species, such as Ipomoea purpurea, often grown as annuals in temperate climates. These plants have characteristically large, heart-shaped leaves. In contrast, the most aggressive weed commonly called morning glory is Field Bindweed (Convolvulus arvensis), which is a true perennial.
Field Bindweed is smaller and less showy than its ornamental relatives, possessing arrow-shaped leaves and smaller, usually white or pale pink flowers. Another perennial nuisance is Hedge Bindweed (Calystegia sepium), which has larger, triangular leaves. Recognizing these differences is the first step in determining whether a plant is a welcome climber or an aggressive invader.
Why It Is Classified as a Nuisance
The notoriety of weedy varieties stems from highly effective survival mechanisms that allow them to out-compete and overwhelm other vegetation. The primary reason for control difficulty is their extensive, perennial root system, which acts as a massive underground energy reserve. Field Bindweed roots can descend 15 to 30 feet, making manual extraction nearly impossible.
These deep roots and associated rhizomes allow the plant to survive prolonged drought and readily regenerate even if the top growth is repeatedly cut back. Furthermore, any small fragment of a broken root left in the soil can sprout into a new, independent plant. Casual tilling or digging often spreads the problem rather than solving it. This regenerative capacity makes the plant a formidable foe in cultivated areas.
Above ground, the plant’s aggressive vining habit rapidly creates dense, tangled mats that smother desirable plants by blocking sunlight. The coiling stems wrap tightly around other vegetation, choking out growth and competing for water and nutrients. The plant also produces prolific seeds that remain viable in the soil for decades, sometimes up to 50 years. This long-term seed bank ensures the problem persists long after the parent plant has been managed.
Controlling Unwanted Morning Glory
Effective control requires a persistent, multi-year strategy to exhaust the plant’s massive underground nutrient reserves. Non-chemical methods focus on starving the root system by preventing photosynthesis. This involves relentlessly cutting or pulling above-ground stems as soon as they appear, ideally every one to three weeks, to deplete the energy stored in the deep roots.
Smothering is another labor-intensive, effective non-chemical approach, using thick layers of opaque mulch or landscape fabric to exclude all light from the soil surface. This method must be maintained for at least two to five years to fully deplete the perennial root structure. Complete manual removal is rarely feasible for established plants because the entire root system must be extracted.
For chemical control, systemic herbicides like glyphosate or products containing 2,4-D are the most effective options. They are absorbed by the leaves and translocated to the extensive root system. Timing is critical to maximize effectiveness against perennial weeds. Best results occur when the plant is actively growing and transporting sugars down to the roots, typically during the bud to full bloom stage or fall regrowth. Multiple applications over several seasons are required, as a single treatment rarely eliminates the deep-rooted network entirely.