When landscapers spray a distinctively colored product, often neon green or blue, it raises questions about the materials being used. The term “green weed killer” actually refers to two concepts: non-synthetic, naturally derived herbicidal products and the literal use of temporary green dye for application purposes. Understanding this distinction clarifies what is being applied to landscape areas.
Identifying the Professional “Green” Herbicides
The non-synthetic products that fit the “green” description fall into two categories: highly concentrated acetic acid and specific fatty acid compounds. Concentrated acetic acid, a much stronger version of household vinegar, is a popular non-selective herbicide choice for professionals seeking non-glyphosate alternatives. While household vinegar contains 4% to 6% acetic acid, horticultural-grade products are typically sold at concentrations of 10% to 20% or higher.
Another common class of professional “green” products involves naturally derived fatty acids, such as pelargonic acid or capric acid. Pelargonic acid occurs naturally in plants and is often used in fast-acting, organic-approved herbicide formulations. These fatty acid-based products offer rapid results, often showing visible effects within hours, making them desirable for quick-turnaround landscape maintenance.
The literal green color seen in spray applications is usually a temporary marker dye added to the tank mix, not the herbicide itself. This dye, which can be green, blue, or pink, serves a practical purpose for the applicator. It allows the landscaper to clearly see where the product has been applied, preventing missed spots or overlapping coverage. The color additive is not necessary for effectiveness and breaks down quickly in sunlight.
How Natural Contact Killers Function
The mode of action for these professional-grade natural herbicides is distinctly different from traditional systemic weed killers. Both concentrated acetic acid and fatty acid products are classified as non-selective contact herbicides. This means they only damage the plant tissue they directly touch, rather than being absorbed and transported throughout the plant system.
When applied to the foliage, the high concentration of the active ingredients causes a rapid breakdown of the plant’s cellular structure. Acetic acid works by disrupting the cell membranes, which leads to the leakage of cellular contents. This rapid cellular destruction results in desiccation, or extreme drying out, of the green tissue.
Fatty acid-based products like pelargonic acid also function by destroying the integrity of the leaf surface and cell walls. Because these products are not systemic, they do not translocate to the roots, which is why they are most effective on young, small annual weeds. Perennial weeds with established root systems often survive the contact application and regrow, requiring multiple treatments.
Safety and Environmental Impact
While these professional products are marketed as “natural,” the high concentrations require careful handling and pose significant safety risks if misused. Herbicidal acetic acid at 20% concentration or more is corrosive, carrying a “DANGER” signal word on its label from regulatory bodies. Exposure to the eyes can cause severe irritation and possible irreversible damage, including blindness.
The high corrosiveness means applicators must utilize personal protective equipment, such as gloves and eye protection, which is not required for lower-concentration household products. Before drying, the treated areas can also be corrosive to skin. This necessitates keeping children and pets away until the solution has completely dried.
From an environmental standpoint, these natural contact killers are considered less persistent than many synthetic alternatives. Acetic acid breaks down rapidly in the environment, often within a few days, and leaves no active soil residue. Similarly, pelargonic acid has no soil activity, limiting its environmental impact to the immediate application area. This rapid breakdown and lack of residual effect means these products are often approved for use in organic operations.