How long does weed and feed take to work?

Weed and feed is one of the most popular lawn products for killing weeds and fertilizing your lawn. It’s a combination of herbicides that tackle the most common weeds and nutrients that will help your lawn grow thicker and greener.

Under the right conditions, you will start to see some results in about a week and it will take from 3 weeks to a month to rid all visible weeds from your lawn and the lawn to grow thicker. Several factors such as weed type and proper application significantly affect the time needed for weed and feed to work.

It is available as a pre-emergent and post-emergent formula. Stay with me to find out more about this subject.

How long does weed and feed take to work

How long does it take to work and how does it work?

Usually, it takes from 3 weeks to a month to see complete weed and feed results. However, the effects of the fertilizer components in the product should begin to work in the first five days after application.

The active ingredients in the mixture will attack the weeds in your lawn without harming the grass. Herbicides work by attacking the plant system to kill weeds down to the root. It takes time but the results are great.

Weed and feed formulas

Weed and feed are sold under many different names, but in general, it is available as pre-emergent and post-emergent formula.

Pre-Emergent formula

Pre-emergent formulas gave the best results against weeds such as crabgrasses and most broadleaf weeds. It stops weeds from appearing in the first place, so the kill happens during the very early phase.

The time to death can vary from formula to formula but occurs between the time when the weed seed germinates and when the resulting sprout emerges through the soil. Most of the pre-emergent herbicides are active between six and eight weeks so you should apply them in spring before weeds appear because any weed that sprouts during the period of effectiveness will likely die.

Pre-emergent formulas will only prove they are working when you don’t see new weeds sprouting.

Post-Emergent formulas

Post-emergent formulas kill weeds that are already growing. The time of action of this type of formula ranges from 5 days when the first results are noticed until complete extermination of the weeds, that is about 20 to 25 days after the initial application.

Timing is everything… Don’t expect results with post-emergent formulas unless it is applied at the proper time, i.e., when the weeds are actively growing. Also, it is very important to wait a few days after moving, because mowing puts them in a temporarily dormant state.

The best time to apply post-emergent weed and feed is fall when weeds are actively growing but have not yet to seeded. Waiting until after weeds have seeded will just prolong the problem.

The working time can vary from one brand to another, but they generally work between seed germination and sprout emergence from the soil surface.

Tips for best results

The weed and feed provide excellent results if applied correctly. Follow these tips when applying either formula type:

  • The product works best when used in temperatures from 60 to 90 Fahrenheit degrees;
  • In early spring use pre-emergent formula while from late summer to early fall go with a post-emergent one;
  • The lawn should be slightly damp but not wet, so early morning application works best;
  • If you apply it later in the day slightly sprinkle your lawn;
  • Wait a few days after mowing;
  • To ensure even distribution use a lawn spreader when applying;
  • After applying wait at least 24 hours before watering, and 48 hours before mowing.

How can you tell that weed and feed work?

There are a few crucial time frames in which you should see some results from the product, and you can tell that your job is successful. These time frames differ from one brand to another but you can use them as an orientation:

  • First 24 hours: About 24 hours are enough for weed and feed to be fully absorbed, so don’t expect results before;
  • The first week: Since fertilizers work faster than herbicides you will begin to see thicker and greener grass in your lawn;
  • After 7 days: The weeds will gain a yellow hue and will start to wilt;
  • Days 15 to 21: Crabgrass and other thin-leaf weeds should be willed and brown, and easy to remove. Broadleaf weeds will begin dying;
  • After 30 days: Everything except the hardiest broadleaf weeds should be dead and can be removed, while the grass is a lush and vivid green and denser than before.
Note: You can calculate the exact amount of fertilizer needed for your lawn per square foot by using this calculator.


Once the application of the weed and feed mixture is done let it rest on the grass for two days, then water it thoroughly. During this 2-day period, the flat weeds should be burned. Watering after 2 days will help release the iron and nitrogen. They will be absorbed by the root system to provide strong green growth.

When summer arrives and weeds are up on the lawn it is too late to apply the weed and feed since fertilizer applications are not recommended in summer. Also, established ornamentals can suffer from weeds and feed formulas if they are applied in conditions such as temperatures above 90 degrees F.

This sort of chemical structure remains in the soil long after it’s killed the weeds. Studies on weed control have shown that chemical structures could help the absorption by the soil and remain in the soil for up to 20 years.

Find out how much your job will cost