Weed & Feed Calculator
Find out when to apply weed & feed in your area and exactly how much to buy. Get spring and fall timing by ZIP, bags or quarts needed, spreader settings, and grass-safety checks.
Tool inputs
2 minutesWeed & feed timing, amounts, and grass safety
Weed & feed is a combination product: a granular fertilizer carrying a post-emergent herbicide. The granules have to stick to the leaves of actively growing weeds, which is why most labels tell you to apply to wet or dew-damp grass and then hold off watering for 24 hours. The fertilizer greens up your whole lawn while the herbicide kills the broadleaf weeds it lands on.
Weed & feed works when weeds are actively growing: after your second or third mow in spring, and again in early fall while daytime temps sit between 60 and 85°F. Your exact window depends on where you live.
| Region | Spring window | Fall window | Notes |
|---|---|---|---|
| Northeast | May 1 – June 15 | September 1 – October 1 | Wait for 2-3 mows; cool springs run late |
| Mid-Atlantic | April 15 – June 1 | September 1 – October 15 | Fall is the stronger window for fescue |
| Southeast | April 1 – May 15 | September 15 – October 31 | Use the atrazine rule for St. Augustine / centipede |
| Great Lakes | April 20 – June 5 | September 1 – October 10 | Skip during summer heat stress |
| Upper Midwest | May 1 – June 15 | August 25 – October 1 | Short season; do not push past early October |
| Central | April 10 – May 25 | September 5 – October 15 | Watch the wind on spray days |
| South Central | March 15 – May 1 | September 15 – November 1 | Stop once highs pass 90°F |
| Mountain West | May 1 – June 15 | September 1 – October 1 | Water in well; dry air slows uptake |
| West Coast | April 1 – May 30 | September 15 – November 1 | Long, forgiving window along the coast |
| Florida | March 1 – April 15 | October 1 – November 15 | Nearly year-round growth; atrazine products only |
Pre-emergent combos like Scotts Triple Action apply earlier, before soil reaches 55°F. Enter your ZIP in the calculator for your product-specific dates.
Every product covers a set square footage per bag. Buy by coverage, not weight, and never double up to hit weeds harder. Extra herbicide stresses your grass without killing more weeds.
| Product | N-P-K | Sizes | Safe on |
|---|---|---|---|
| Scotts Turf Builder Weed & Feed 3 | 28-0-3 | 5k / 15k sq ft | Bermuda, Zoysia, Tall Fescue, Kentucky Bluegrass |
| Scotts Turf Builder Triple Action | 25-0-2 | 4k / 12k sq ft | Bermuda, Zoysia, Tall Fescue, Kentucky Bluegrass |
| Scotts Turf Builder Bonus S Southern Weed & Feed | 29-0-10 | 5k / 10k sq ft | St. Augustine, Centipede, Zoysia |
| Fertilome Centipede Weed & Feed 15-0-15 | 15-0-15 | 5k sq ft | Centipede, St. Augustine |
| Southern Ag Atrazine (liquid) | 0-0-0 | 32 oz quart | St. Augustine, Centipede |
Most lawns need at most 2 weed & feed applications per year. More than that risks herbicide damage and exceeds label limits.
- Spring pass: after your 2nd or 3rd mow, apply to wet grass in the morning so granules stick to weed leaves. Hold off if rain is due within 24 hours.
- Summer: hands off. No weed & feed above 90°F. Spot-spray stragglers instead, and keep watering deep and infrequent.
- Fall pass: your second and final application of the year. Weeds are pulling energy to their roots, so the herbicide travels with it.
The herbicide in weed & feed matters more than the fertilizer. Match the family to your grass first.
| Grass type | 2,4-D (phenoxy) | Atrazine |
|---|---|---|
| Bermuda | Safe | Damages grass |
| Zoysia | Safe | Safe |
| St. Augustine | Damages grass | Safe |
| Centipede | Damages grass | Safe |
| Tall Fescue | Safe | Damages grass |
| Kentucky Bluegrass | Safe | Damages grass |
This is a general guide. The calculator applies each product's specific label restrictions when you pick your grass type.
When should I apply weed & feed?
In spring after your second or third mow, once weeds are actively growing and daytime temps are between 60 and 85°F. A second application in early fall catches weeds storing energy for winter. Enter your ZIP above for your exact windows.
How long does weed & feed take to work?
Weeds start curling within 5 to 7 days and die back over 2 to 4 weeks. The fertilizer greens up your lawn within a week. If weeds look untouched after 3 weeks, they may not be listed on the label or the granules did not stick to wet leaves.
Should I mow before or after applying weed & feed?
Mow 1 to 2 days before, then wait 2 to 3 days after applying before mowing again. The herbicide needs time on the leaf surface, and you should keep the first few rounds of clippings out of the compost.
Do I water before or after weed & feed?
Most granular weed & feeds go down on wet or dew-damp grass so the herbicide sticks to weed leaves, then you hold off watering for 24 hours. Pre-emergent combos like Triple Action are the opposite: apply to a dry lawn and water them in. Always follow the bag, and skip application if rain is due within 24 hours.
Is weed & feed safe on St. Augustine?
Only atrazine-based products like Scotts Bonus S. Standard 2,4-D weed & feed will yellow and thin St. Augustine and centipede lawns. This calculator checks that automatically when you pick your grass type.
How soon after seeding can I apply weed & feed?
Wait until new grass has been mowed 3 to 4 times, roughly 4 to 6 weeks after germination. Pre-emergent products like Triple Action are stricter: do not seed for 4 months after applying.
How often can I apply weed & feed?
Twice per year maximum for nearly every product, with at least 2 months between applications. More does not kill more weeds; it just stresses your grass and exceeds the label limits.
When is it safe for pets and kids to go back on the lawn?
Keep pets and children off until the product is watered in (or the spray has dried) and the lawn is fully dry, usually 24 to 48 hours. Follow the specific re-entry interval printed on your product label.