Funnel weed is the common name for Field Bindweed (Convolvulus arvensis), a persistent and problematic invasive perennial vine. It is notorious for its aggressive growth and deep root system, making it difficult to manage in agricultural fields and residential gardens. Its successful spread is due to dual propagation methods and its ability to store massive amounts of energy underground.
Identifying the Funnel-Shaped Invasive
Funnel weed (Convolvulus arvensis) is a tenacious perennial member of the morning glory family. Its common name comes from its distinctive small flowers, which are shaped like a trumpet or funnel. These blossoms typically measure about one inch across and can be white, pink, or a combination of both colors.
The leaves are often spade-shaped or arrowhead-shaped with rounded ends. Field Bindweed grows as a twining vine, with smooth, slender stems that wrap around nearby support structures or spread across the ground. It is important to distinguish this species from similar relatives. Hedge Bindweed (Calystegia sepium) has larger flowers, while Black Bindweed (Fallopia convolvulus) has inconspicuous, greenish-white flowers instead of the prominent funnel shape.
Aggressive Root Systems and Propagation
The primary reason this weed is difficult to eradicate lies in its extensive and deeply penetrating root system. The vertical roots, or rhizomes, can extend to depths of 20 to 30 feet, though most of the plant’s biomass is within the top one to two feet. This vast underground network stores significant carbohydrates, allowing the plant to survive harsh conditions and quickly regrow after foliage is removed.
The weed employs a dual strategy, spreading both vegetatively and through seeds. New plants can sprout from root fragments as short as one inch. This regenerative ability means that common practices like tilling can inadvertently worsen the problem by distributing root pieces. Furthermore, the durable seeds possess a hard coat, allowing them to remain viable in the soil for 20 to 30 years.
Detrimental Effects on Gardens and Agriculture
The aggressive growth habit of funnel weed causes significant issues for cultivated areas. As a vining plant, its stems twine tightly around desirable plants and crops, strangling them and causing structural damage. The dense, tangled mats formed by the vines can dominate local plant communities, reducing the aesthetic value of lawns and gardens.
Underground, the extensive root system aggressively competes with surrounding vegetation for limited resources. This competition for soil moisture and nutrients weakens or suppresses the growth of crops and garden plants. The plant contains toxic compounds that can cause gastrointestinal distress in pets and humans if ingested in large quantities.
Effective Control and Removal Techniques
Controlling Field Bindweed requires a long-term, persistent approach combining mechanical and chemical strategies due to its deep root reserves. Non-chemical control relies on exhausting the root system by preventing photosynthesis. Persistent hand-pulling or hoeing must be performed meticulously, cutting off all shoots every 10 to 14 days to deplete stored energy.
Smothering is another non-chemical technique, requiring thick, opaque materials like heavy mulches or black plastic to block sunlight completely. Mechanical cultivation, such as repeated tilling, is effective only if performed frequently—every two to three weeks for up to two years—to continuously disrupt the plant’s recovery. Pre-emergent herbicides that target seedlings are ineffective against mature infestations because of the deep roots.
Chemical control involves using systemic post-emergence herbicides, which are absorbed by the leaves and transported down to the root system. Glyphosate-based products are most effective when applied in the fall, when the plant is actively moving sugars down to its rhizomes for winter storage. For control in lawns, herbicides containing quinclorac or three-way mixtures of dicamba, 2,4-D, and MCPP/MCPA provide results. Repeat applications over multiple growing seasons are necessary to achieve long-term suppression of this tenacious weed.