Deciding whether to pull weeds or apply herbicide first is a common dilemma for anyone maintaining a yard or garden. Both manual removal and chemical control are effective, but the order significantly impacts long-term success. The correct sequence is not universal; it depends entirely on the type of weed you are treating and the specific chemical product you intend to use. Understanding the underlying science of how herbicides function is necessary to make the most efficient and effective choice.
The Foundation: Types of Herbicides and Their Action
Chemical weed control is divided into two primary categories based on when they are applied in the weed’s life cycle. Pre-emergent herbicides are designed to be applied to the soil before weed seeds germinate, forming a chemical barrier that prevents the seedling from successfully emerging from the ground. These products work by disrupting cell division in the root tip of the newly sprouted plant, which effectively stops growth before it is visible.
Post-emergent herbicides, in contrast, are applied to weeds actively growing above the soil line. This category is further separated by its mode of action within the plant. Contact herbicides kill only the parts of the plant they directly touch, causing the foliage to quickly wither and brown, though the root system may remain intact. Systemic herbicides are absorbed by the leaves and then translocated throughout the entire plant, including the roots, to achieve a complete kill.
Strategy 1: Why You Should Spray Before Pulling
Spraying before pulling is the preferred strategy when dealing with perennial weeds and stubborn annuals that have deep, extensive root systems. This approach is specifically reliant on using a systemic, post-emergent herbicide. These chemicals must be absorbed by the weed’s leaves to be effective, as the leaves act as the entry point for the chemical.
Once absorbed, the systemic herbicide travels through the plant’s vascular system down to the root structure. This translocation ensures the complete destruction of the weed, preventing regrowth from a surviving root fragment. Pulling the weed prematurely, even a day or two after application, removes the foliage before the chemical has had sufficient time to travel to the roots. By removing the leaves, you are essentially eliminating the “delivery system” for the herbicide, which makes the application ineffective and allows the root to survive.
To ensure that the systemic chemical has fully translocated, a waiting period is necessary before any manual removal is attempted. For many common systemic products, this waiting period is often recommended to be between 7 and 14 days. During this time, the weed’s appearance may not immediately change, but the herbicide is actively moving through the plant to kill the entire organism. Allowing the weed to die completely in place ensures that the energy reserves in the root are depleted, preventing the weed from growing back.
Strategy 2: Why You Should Pull Before Spraying
In certain situations, manual removal is the most logical first step, especially when chemical application is not the primary goal or most efficient method. This method is best used for very large weeds or in areas being treated with a pre-emergent product. Pre-emergent herbicides require the removal of all existing plant material first to create the necessary chemical barrier on the soil surface.
Pulling exceptionally large weeds before spraying can be a matter of efficiency and cost savings. A large weed requires a greater volume of post-emergent spray to cover its extensive leaf surface area. Removing the largest weeds first significantly reduces the amount of chemical needed, allowing the remaining spray to be directed at smaller, underlying weeds that are often obscured by the large canopy. This also ensures that the smaller weeds receive direct spray contact for better absorption.
If a weed has already produced mature seed heads, the physical act of pulling is also beneficial for containment. Spraying a weed that has gone to seed will kill the plant, but it does nothing to prevent the mature seeds from falling to the soil and germinating later. Carefully removing and bagging the weed prevents the dispersal of new seeds, proactively managing future infestations.