How long After Weed Killer can I Plant Grass Seed

There’s nothing better than spending your summertime playing with your kids and enjoying the sun on your beautiful lawn. Unfortunately, the emergence of weeds can change your lawn’s appearance.

Different weed killers have different waiting times after applying the weed killer. That’s why it’s always good to be cautious when sowing seeds after using a weed killer because some herbicides are harmful to actively growing seedlings and young plants. While some weed killers require you to wait for several months after applications, others only require you to wait a few days. The difference is in the effect of the active chemical used in each herbicide.

Types of weed killers

Selective weed killer

Most selective weed killers are very effective and garden-friendly so they leave little to no trace in the soil.

They only target particular plants and leave the rest unharmed and generally destroy either broadleaf weeds or grassy weeds.

You can safely plant your vegetable and flower seeds a day after applying the selective herbicide like bentazon for grassy weeds because it will only affect plants in the grass family. For your lawn, the broadleaf herbicide is very effective, but you should wait a month after applying the herbicide to reseed your lawn.

Glyphosate weed killer

This is a very effective systemic, non-selective herbicide that kills the entire weed plant from the leaves to the roots, but it doesn’t leave any residue in the soil.

It will kill weeds, grasses, and other desirable plants, but once the soil absorbs the liquid it doesn’t pose any more threat.

After application, it’s safe to sow ornamental flower seeds and grass and sow your vegetable and grass seeds 3 days after, even though it will take 7 days to destroy the weeds.

If you pluck the dying weeds too soon, you may leave some live roots in the soil that will regrow.

Pre-emergent weed killer

This weed killer prevents seeds from sprouting by creating a chemical barrier on the soil surface. These herbicides take about a month of waiting after application to sow your grass seeds.

Some of these herbicides only affect grassy weeds so you can safely sow your vegetable and flower seeds after application.

However, grass seeds won’t sprout until the weed killer has decayed and become ineffective.

Types of weed killers



The period to work

Contact weed killer

Living and green weeds and gets absorbed by the leaves

Takes 2 weeks to work

Systemic weed killer

Absorbed by any part of the plant

Take up to 7 days to work

Residual weed killers

Only applied in areas like paths and patios

Stays in the ground for months

Selective weed killer

Targets specific plants

Stys up to 7 days in the soil

Non-selective weed killer

Kills all plants it comes in contact with

Stay in the soil for 2-4 weeks


When you spray a weed killer you expect to see results, but different weed killers available in the market take different times to give results. That’s why you need to know the best time to spray the weed killer, the waiting period before you see results, and the best time to plant after application.


Is it OK to spray herbicide after it rains?

After it rains, wait until the leaves dry before spraying them. It can take hours, especially if there’s high humidity or it’s cool.

How long does it take for weeds to die after spraying?

Generally, it takes 2-4 weeks to completely get rid of all the unwanted plants on your lawn or garden.

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