What Does Weed and Feed Do? | Fertilizer & Weed Killer In One

Weed and feed is a dual-action lawn product that applies fertilizer to nourish grass and herbicide to kill broadleaf weeds in a single pass.

One trip around the yard with a spreader drops two things at once: a nitrogen-heavy fertilizer that greens up the lawn, and a mix of herbicides that target dandelions, clover, and over 200 other broadleaf weeds. The fertilizer thickens the grass, which naturally crowds out new weeds, while the chemicals take down what’s already growing. The trick is applying it at the right time and temperature or the whole thing falls flat.

How Weed and Feed Actually Works

The science behind it is straightforward. Granules land on the lawn and stick to the wet leaves of broadleaf weeds, delivering the herbicide directly. The fertilizer inside the same pellet feeds the grass roots once it dissolves into the soil. Each major brand tweaks the formula.

• Scotts Turf Builder Weed & Feed: 28-0-3 NPK with four specific herbicides targeting broadleaf weeds.
• Pennington Full Season Weed & Feed: 25-0-8 NPK plus 5% iron for deep greening, uses polymer-coated urea that releases nitrogen over up to 4 months.

Selective herbicides like 2,4-D and dicamba kill the broadleaf plants but leave grass untouched. The grass species in your lawn determines compatibility — check the label before you buy.

When To Apply Weed and Feed For Best Results

Timing makes or breaks this product. Apply it when the grass is actively growing and the weeds are visible and leafed out. The calendar depends on where you live.

Stay between 60°F and 90°F — applying outside that range damages the grass or reduces the herbicide’s punch. One application usually does it for northern lawns. Southern lawns sometimes need a second round because warm-season grass stays active longer.

How To Apply Weed and Feed Step By Step

Doing it right takes about 30 minutes of prep and 15 minutes of spreader work. Here’s the sequence that works.

Preparation

• Mow the lawn 1–2 days before application. Leave the clippings.
• Apply when the grass and weeds are wet — dew in the morning or a light sprinkling if it’s dry. Granules need moisture to stick to broadleaf leaves.
• Check the forecast. No rain within 24 hours, or the granules wash off before the herbicide can work.

Application

• Use a rotary broadcast spreader for granules or a sprayer for liquid formulations.
• Set the spreader rate. For Scotts, that’s 0.9 lb per 250 sq ft, roughly 3.6 lb per 1,000 sq ft. Adjust walking speed: slower means a higher rate, faster means lower.
• Walk in one direction for full coverage with slight overlap between passes. A two-pass criss-cross pattern at half the rate is also acceptable — just don’t double the amount.

Post-Application

• Leave the product undisturbed for 24 hours. No watering, no walking on it, no pets on the lawn.
• After 2 days, water the lawn to dissolve the fertilizer and push nutrients to the roots.
• Leave the clippings on the lawn for the next three mows. Do not compost them or use them around vegetable gardens or ornamentals — the herbicide residue can damage sensitive plants.

What Weed And Feed Won’t Do

It handles broadleaf weeds well, but it has limits. The selective herbicides in standard weed and feed won’t kill grassy weeds like crabgrass or nutsedge — those need different products. And if the lawn is stressed from heat, drought, or recent seeding, the herbicide can do more damage than good. New lawns and areas you plan to seed are off-limits until the grass is established.

Some turf experts argue that weed and feed harms soil microbiology over time, and that building soil health with compost and overseeding is a stronger long-term strategy. That’s a fair counterpoint, but for most homeowners who want a green lawn and fewer dandelions in a single afternoon, weed and feed gets the job done.

Common Mistakes That Wreck The Results

• Applying to dry grass: The granules bounce off weed leaves instead of sticking. Result: weeds survive.
• Applying too early: If the grass is still dormant or hasn’t been mowed twice, the herbicide hits nothing active.
• Applying above 90°F: The grass burns. The herbicide volatilizes and drifts onto neighboring plants.
• Overlapping too much: Double-dosing burns patches into the lawn.
• Raking before the first mow: Breaks the pre-emergent barrier the granules laid down.

If you are shopping for the right product, check out our tested roundup of the best lawn weed and feed products for this season’s top picks.

Weed and Feed vs. Separate Fertilizer And Herbicide

The combined product wins on convenience. Separate products win on precision. For most lawns with a moderate weed load, weed and feed is the sensible middle ground.

Checklist: Your Weed And Feed Application

• ☐ Confirm grass type is listed on the product label
• ☐ Check 7-day forecast — no rain within 24 hours, temp between 60°F and 90°F
• ☐ Mow 1–2 days before
• ☐ Apply to wet grass and weeds (dew or light watering)
• ☐ Set spreader to the labeled rate; walk one direction with slight overlap
• ☐ Do not water for 24 hours; water on day 2
• ☐ Leave clippings for three mows; do not compost
• ☐ Avoid heavy raking until after the second mow