Skip to main content
What Grass Is This? LogoWhat Grass Is This?
Seasonal tool

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 minutes
Location
Grass type
Lawn details
Get your lawn plan, journal, and reminders in the free iPhone app
Download on theApp Store

Weed & feed timing, amounts, and grass safety

How weed & feed works

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.

The herbicide family matters more than the fertilizer. A 2,4-D (phenoxy) product damages St. Augustine and centipede; an atrazine product damages fescue and bluegrass. Match the product to your grass before you think about the numbers.

When to apply weed & feed by region

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.

Swipe sideways to see every column.

RegionSpring windowFall windowNotes
NortheastMay 1 – June 15September 1 – October 1Wait for 2-3 mows; cool springs run late
Mid-AtlanticApril 15 – June 1September 1 – October 15Fall is the stronger window for fescue
SoutheastApril 1 – May 15September 15 – October 31Use the atrazine rule for St. Augustine / centipede
Great LakesApril 20 – June 5September 1 – October 10Skip during summer heat stress
Upper MidwestMay 1 – June 15August 25 – October 1Short season; do not push past early October
CentralApril 10 – May 25September 5 – October 15Watch the wind on spray days
South CentralMarch 15 – May 1September 15 – November 1Stop once highs pass 90°F
Mountain WestMay 1 – June 15September 1 – October 1Water in well; dry air slows uptake
West CoastApril 1 – May 30September 15 – November 1Long, forgiving window along the coast
FloridaMarch 1 – April 15October 1 – November 15Nearly 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.

How much weed & feed to use

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.

Swipe sideways to see every column.

ProductN-P-KSizesSafe on
Scotts Turf Builder Weed & Feed 328-0-35k / 15k sq ftBermuda, Zoysia, Tall Fescue, Kentucky Bluegrass
Scotts Turf Builder Triple Action25-0-24k / 12k sq ftBermuda, Zoysia, Tall Fescue, Kentucky Bluegrass
Scotts Turf Builder Bonus S Southern Weed & Feed29-0-105k / 10k sq ftSt. Augustine, Centipede, Zoysia
Fertilome Centipede Weed & Feed 15-0-1515-0-155k sq ftCentipede, St. Augustine
Southern Ag Atrazine (liquid)0-0-032 oz quartSt. Augustine, Centipede

Your annual weed & feed schedule

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.

Which herbicide is safe on your grass

The herbicide in weed & feed matters more than the fertilizer. Match the family to your grass first.

Swipe sideways to see every column.

Grass type2,4-D (phenoxy)Atrazine
BermudaSafeDamages grass
ZoysiaSafeSafe
St. AugustineDamages grassSafe
CentipedeDamages grassSafe
Tall FescueSafeDamages grass
Kentucky BluegrassSafeDamages grass

This is a general guide. The calculator applies each product's specific label restrictions when you pick your grass type.

Frequently asked questions

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.

What does weed and feed do for lawn care?

It is usually a two-in-one lawn care product: a broadleaf herbicide that kills the weeds you can already see, plus a nitrogen fertilizer that thickens the grass so new weeds have less room to start. The feed is what turns it from a spot treatment into a maintenance step. Applied on a schedule suited to your product and lawn, it folds weed control and a fertilizer round into one pass.

Is weed and feed a postemergence herbicide?

The weed-killer half is. Standard weed & feed uses postemergence herbicides like 2,4-D, dicamba, or MCPP that act on weeds already growing, which is why you apply it when weeds are actively out. That is the opposite of a pre-emergent like crabgrass preventer, which stops seeds before they sprout. A few combo bags such as Triple Action include both, so check the label.

Related Articles

Pre-Emergent Timing: When to Apply by ZIP CodeScotts Weed and Feed Application GuidePre-Emergent Herbicide Timing Guide