The aggressiveness of morning glories depends on the specific species being observed. The common name “morning glory” refers to over 1,000 species of flowering plants belonging to the family Convolvulaceae. This broad category includes desirable annual vines, typically from the Ipomoea genus, and persistent perennial weeds, often classified under Convolvulus or Calystegia. Managing growth requires understanding the specific species, as ornamental varieties spread mostly by seed, while weedy types rely on deep, tenacious root systems.
How Morning Glories Propagate
Morning glories employ two primary mechanisms to spread: prolific seed production and vegetative root growth. Many species produce seeds with an exceptionally hard outer shell, which contributes to their longevity. This hard seed coat allows seeds to remain dormant for decades, creating a persistent “seed bank” that results in new plants emerging annually.
The plant’s vining habit also contributes to its dominance by rapidly climbing and twining around other vegetation, competing for sunlight. Perennial varieties, such as Field Bindweed, spread laterally through an extensive underground network of roots and rhizomes. These root systems can penetrate the soil to depths of 20 feet or more, enabling the plant to survive harsh conditions. Even a small piece of root can regenerate into a new plant, which is why mechanical disturbance often worsens the problem.
Differentiating Between Invasive and Ornamental Varieties
Distinguishing between ornamental annuals and aggressive perennial weeds is essential for management. Cultivated morning glories (Ipomoea species) are generally annuals in cooler climates, meaning they complete their life cycle in a single season. They typically have distinct heart-shaped leaves and are less destructive because they lack the deep, rhizomatous root system of their weedy relatives.
The perennial “bindweeds” (Convolvulus and Calystegia) are the aggressive spreaders. Field Bindweed (Convolvulus arvensis) features smaller, trumpet-shaped flowers, about an inch across, and distinct arrow- or spade-shaped leaves. Hedge Bindweed (Calystegia sepium) has larger flowers and leaves that are more distinctly arrowhead-shaped with deep, pointed lobes. The extensive, carbohydrate-storing root network of these perennial varieties makes them difficult to eradicate, as they quickly resprout after top growth is removed.
Strategies for Managing Aggressive Growth
Managing aggressive morning glory growth requires targeting both the seeds and the root system. For annual species, persistent hand-pulling before flowering prevents the formation of a future seed bank. For perennial bindweeds, consistent physical removal of the top growth is necessary to starve the deep root system of solar energy.
Cultural methods are effective at suppressing new growth and controlling the seed bank. Applying a heavy layer of mulch, four to six inches deep, blocks light and suppresses seedling germination. Another method is soil solarization, which involves covering the affected area with clear plastic sheeting during hot summer months for six to eight weeks to heat the soil and kill seeds and root fragments near the surface.
For established perennial infestations, targeted chemical control is often necessary due to the depth of the root system. Herbicides formulated for broadleaf weeds are most effective when applied in the late summer or fall. This timing is strategic because the plant actively transports nutrients down to its roots for winter storage, pulling the chemical deep into the rhizome network. Successful management requires repeated applications and vigilance to address re-emergence from dormant seeds or deep root reserves.