The answer to whether “Weed and Feed” is the same as fertilizer is no, though they are closely related products frequently confused by homeowners. Standard fertilizer serves a purely nutritional function for the lawn, providing the necessary elements for turfgrass to grow dense and green. “Weed and Feed,” however, is a combination product that mixes fertilizer with an herbicide. This gives it a dual purpose of both nurturing the grass and killing or preventing weeds.
The Purpose and Composition of Standard Fertilizer
Standard lawn fertilizer is a nutritional supplement designed to enhance the growth and health of turfgrass. These products are formulated around the three primary macronutrients, represented by the N-P-K ratio printed on the packaging. This ratio indicates the percentage by weight of Nitrogen (N), Phosphorus (P), and Potassium (K) in the product.
Nitrogen (N) is responsible for vegetative growth and contributes significantly to the grass blade’s lush green color by supporting chlorophyll production. Phosphorus (P) plays a role in energy transfer and is largely responsible for developing a strong and healthy root system. Potassium (K) aids in regulating water balance and strengthens the plant’s overall resistance to environmental stressors like drought, heat, and disease.
These nutrients are often not present in sufficient concentrations in the soil to support the dense, vibrant growth desired. By providing a measured dose, fertilizer helps the grass grow vigorously, which naturally aids in crowding out weeds. Fertilizers can also contain micronutrients like iron, which assists in chlorophyll production.
How “Weed and Feed” Differs: The Herbicide Component
The fundamental difference between pure fertilizer and “Weed and Feed” is the inclusion of a selective herbicide. This component is designed to target and eliminate unwanted broadleaf weeds and grassy weeds without damaging the turfgrass itself. The product attempts to achieve two separate goals—feeding and weed control—with a single application.
The specific function of a “Weed and Feed” product is determined by the type of herbicide it contains.
Pre-Emergent Herbicides
Pre-emergent herbicides prevent weed seeds from successfully germinating by inhibiting cell division in the young root system. This type of product is a preventative measure, creating a chemical barrier in the soil. It controls weeds before they even become visible by stopping the weed life cycle at the seed stage.
Post-Emergent Herbicides
Alternatively, a “Weed and Feed” may contain a post-emergent herbicide, designed to kill existing weeds that have already sprouted. These chemicals are systemic, meaning they are absorbed by the weed’s foliage and translocated throughout the plant to the root system, killing the weed completely. The fertilizer is merely a carrier for the herbicide, and its application method must prioritize the herbicide’s requirements.
Strategic Application: When to Use Each Product
The timing and conditions for application highlight the practical differences between fertilizer and “Weed and Feed.” Pure fertilizer should be applied when the grass is actively growing to maximize nutrient absorption. It is the preferred choice when the lawn is largely weed-free or when a homeowner is seeding.
Application Considerations
Using a “Weed and Feed” product that contains a pre-emergent herbicide is not advisable when overseeding or planting new grass. The chemical barrier that prevents weed germination will also prevent the desirable grass seed from sprouting. Pre-emergent products are applied in early spring or late fall, before soil temperatures are conducive to weed seed germination. The application must be watered in promptly to activate the herbicide and establish the barrier.
Products containing post-emergent herbicides, which target visible weeds, require a different strategy for effectiveness. The granules must stick to the weed leaves, so application should occur when the foliage is damp, often in the early morning when dew is present. Post-emergent applications are most effective when weeds are actively growing and not stressed by high heat or drought. Applying any “Weed and Feed” product during extreme heat can cause the chemicals to burn the turf, a risk not associated with pure fertilizer.