Borax is the common household name for sodium tetraborate decahydrate, a naturally occurring mineral salt often utilized as a laundry booster and general cleaning agent. This compound contains the element boron, which is responsible for its herbicidal properties. When applied at high concentrations, Borax acts as a non-selective killer, eradicating grass and other vegetation. While effective for clearing unwanted growth, its use carries significant risks for the surrounding environment, particularly the soil.
How Boron Causes Toxicity in Plants
Boron is a required micronutrient for healthy plant growth, playing a role in cell wall structure and sugar transport. Plants require only very small amounts of this element to thrive, but the difference between a necessary dose and a lethal one is exceptionally narrow.
When applied in excess, boron disrupts fundamental cellular processes. It causes cross-links within the cell walls, leading to stiffening and reduced plasticity, which hinders the plant’s ability to expand and transport nutrients. The overaccumulation also leads to oxidative stress, impairing photosynthesis and causing cell membranes to break down. Visible symptoms start with chlorosis (yellowing) of the leaf margins, followed by necrosis (browning and eventual death of the tissue).
Application Methods for Eradicating Grass
Because of its non-selective nature, Borax is typically used to eradicate grass and weeds in confined areas where future plant growth is not desired. Common application sites include cracks in concrete, patio edges, walkways, and driveways. The high concentrations required make it unsuitable for treating an entire lawn, as the goal is to saturate the target area with a toxic level of boron.
One common method involves dissolving powdered Borax in water to create a liquid application, which is then sprayed directly onto the unwanted foliage. A highly concentrated solution, sometimes as strong as 10 ounces of Borax mixed into 2.5 gallons of water, is necessary to achieve a quick kill. The solution must thoroughly coat the leaves and stems of the grass to ensure the boron is absorbed.
Alternatively, a dry application can be used by sprinkling the Borax powder directly onto the target grass and then lightly watering it to move the compound into the soil. Regardless of the method, Borax must be applied heavily enough to overwhelm the plant’s tolerance for boron. This aggressive application ensures the chemical acts as a potent herbicide, but it also guarantees a high concentration of boron is introduced into the soil beneath the treated area.
Soil Contamination and Persistence
A consequence of using Borax as an herbicide is the lasting contamination of the underlying soil. Unlike many commercial weed killers that break down, boron is a mineral element that does not degrade over time. The sodium tetraborate dissolves in water, releasing boron, which remains in the soil structure.
The persistence of boron is heavily influenced by soil type. It is highly water-soluble and can leach quickly through sandy soils, potentially moving below the root zone. However, in heavy clay soils or those with high organic matter, boron is held more tightly, remaining toxic to plant roots for extended periods. This persistence means the treated area may become sterile or unsuitable for growing sensitive plants for several years.
To reduce high boron levels in contaminated soil, the primary remediation strategy is leaching, which involves flushing the area with large volumes of water to encourage the downward movement of the boron. This process can be slow and may require multiple attempts, especially in less permeable soils. Care must be taken to prevent contaminated runoff from sterilizing surrounding planting areas or entering local water systems.
Safe Handling and Environmental Considerations
Handling Borax requires specific precautions to protect the user, pets, and the environment from potential harm. As a fine powder, Borax can be an irritant; therefore, protective gear such as safety glasses and chemical-resistant gloves should be worn during mixing and application. Inhalation of the dust should be avoided, making a dust mask advisable, especially when working in poorly ventilated areas.
If ingested in large quantities, Borax can be toxic to humans and animals, potentially causing severe gastrointestinal distress. It is necessary to keep pets and children away from the treated area until the product has dried and the area has been thoroughly watered or rinsed.
The high solubility of boron poses an environmental risk to aquatic ecosystems. Runoff from treated areas can carry boron into ponds, streams, or storm drains, where it can be toxic to fish and other aquatic life even at low concentrations. Therefore, Borax should never be applied near water sources or on sloped ground where rain or irrigation could easily wash the chemical away.