“Hairy Mary” is a common name for Commelina benghalensis, also known as Benghal Dayflower, a highly pervasive weed found in diverse garden and agricultural environments. While Calamus australis is sometimes called “Hairy Mary,” this article focuses on the problematic Benghal Dayflower due to its aggressive growth. Understanding its characteristics and management is crucial for gardeners and agricultural professionals.
Identifying Hairy Mary
Benghal Dayflower is a creeping perennial herb that can also grow as an annual in temperate climates. Its fleshy, light green stems typically grow prostrate along the ground, readily rooting at the nodes, contributing to its spreading habit.
The leaves are ovate to triangular-ovate with parallel veins. A distinguishing characteristic is the presence of reddish or white hairs at the tip of the leaf sheath. Above-ground flowers are small, typically lilac to blue, with two prominent petals that open in the morning and often wilt by midday.
A unique feature of this plant is its production of underground flowers, which are small, white, and do not open. These subterranean flowers are borne on burrowing rhizomes and produce seeds that remain viable for extended periods. The plant also produces above-ground seeds in pear-shaped capsules.
Why Hairy Mary Is a Problem
Benghal Dayflower is a challenging weed due to its aggressive growth and diverse reproductive capabilities. It spreads rapidly through sexual reproduction, via aerial and subterranean seeds, and vegetative means, such as rooting at stem nodes and from rhizomes. Each plant can produce a substantial number of seeds, with aerial seed production being significantly higher than subterranean seed production.
Stem fragments can easily root and establish new plants, even after being detached or tilled. This resilience makes mechanical control methods less effective, as broken pieces can regenerate. The plant’s ability to produce seeds both above and below ground ensures continuous propagation, with subterranean seeds often remaining viable in the soil for several years. These characteristics allow Benghal Dayflower to form dense stands, outcompeting and smothering desired plants.
Effective Control Methods
Controlling Benghal Dayflower infestations requires a persistent approach. Manual removal is effective for small infestations, but it is important to extract the entire plant, including all roots and subterranean flowers, to prevent regrowth. Proper disposal, such as bagging and removing fragments from the site, is advised. Hand-pulling is generally easier when the soil is moist.
Chemical control is often employed for larger infestations. Benghal Dayflower is tolerant to many common herbicides, including glyphosate, which may only provide partial control, especially on mature plants. Multiple applications may be necessary for better efficacy.
Herbicides such as 2,4-D, bentazon, glufosinate, and pelargonic acid have shown some effectiveness. Systemic herbicides, which move throughout the plant, are generally more effective for perennial weeds like Benghal Dayflower than contact herbicides. Combining post-emergence and pre-emergence residual herbicides is often recommended to manage existing plants and prevent new seedlings from emerging.
Prevention Strategies
Preventing Benghal Dayflower establishment is a proactive approach to weed management. Applying organic mulches, such as pine straw, at a depth of 2 to 4 inches can help suppress seed germination and establishment. Mulches create a physical barrier that makes it difficult for seedlings to emerge and can also inhibit rooting of stem fragments.
Regular monitoring and early removal of new seedlings are important to prevent them from becoming established. Maintaining clean gardening tools and equipment is also advised, as viable stem fragments or seeds can be inadvertently transported to new areas. Improving overall soil health can also contribute to weed prevention by promoting the vigorous growth of desirable plants that can outcompete weeds for resources.