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When to apply pre-emergent in North Carolina

If you are in North Carolina and have a problem with weeds on your lawn, don’t wait until they have sprouted to start acting on them.

Pre-emergent weed killers eliminate weeds before they even appear above ground.

Most North Carolina lawn weeds, like those in other regions, are summer and winter weeds. Still, with a proper application of pre-emergent weed killers, you can avoid their infestation altogether.

The weed killers don’t kill the plants but instead attack their roots, effectively interrupting their growth.

If you see weeds that have already appeared above the ground surface, you should use a post-emergent weed killer, or you can try hand-pulling them instead. Just make sure you are using gloves to protect your hands.

To pull this off, you need to carefully observe the average dates when it starts to warm up in spring and the dates when the fall temperatures begin to drop.

This will help you know exactly when to apply pre-emergent in North Carolina to get them before they can emerge.

In North Carolina, the extreme western mountain regions and the coastal plains tend to vary in the average dates that the weather warms up and cools in spring and fall.

The importance of accurate timing

When working with pre-emergent weed killers, timing is critical.

The purpose of pre-emergent is to form a barrier in the soil. This prevents seedlings from getting to the surface of the ground rather than killing the already germinated ones.

A properly timed pre-emergent application will be done one to four weeks before the seeds have germinated.

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Prepare your lawn well before you apply pre-emergent weed killer.

Make sure you have cleared any debris that may have been left on the soil, and if you have any turf or lawn grass thicker than ½ an inch.

You may need to remove it to allow the weed killer to penetrate and get to the seeds below the surface properly.

When to apply pre-emergent weed killer

Whether you are doing it in spring or fall, this article will detail what months you should put down pre-emergent, depending on the season.

1. Applying pre-emergent in spring

The last two weeks of March are often the best time to apply pre-emergent weed killer in most parts of North Carolina.

Pre-emergent herbicides

Crabgrass and dandelion seeds germinate when soil temperatures reach 55 to 60 degrees Fahrenheit or 12.7 to 15.5 degrees Celsius in the summer.

Make sure you apply the pre-emergent and water by the time the temperatures reach that point.

Because temperatures tend to vary yearly, a good trick you can use to tell when the perfect time to apply pre-emergent is to check when the forsythias bloom.

This is before the crabgrass germinates,  a good alternative if you cannot or do not want to track the soil temperatures of your region.

2. Applying pre-emergent in fall

Many of the weeds that appear in the fall remain dormant in the soil during spring and then germinate in fall once the temperatures start to drop.

Chickweed, Carolina geranium, wild mustard, wild onions, and henbit are just a few examples of typical winter annual weeds in North Carolina that can be eliminated by pre-emergent weed killers if applied correctly in the fall.

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To effectively prevent them from taking root in the winter, the best period to apply pre-emergent is from mid-August to the mid-September.

Then, a second application at the beginning of December can stop the late germination from taking root.

Expect temperatures to decrease early if you reside in North Carolina’s far western regions; start applying pre-emergent around the middle of August.

However, you may probably wait for the temperatures to cool down in the coastal areas until September.

How to maintain the lawn after applying pre-emergent

For pre-emergent to work effectively, it needs water to help it fully penetrate the soil.

If you have not received at least ½ an inch of rain within the first two days of applying pre-emergent to the soil, you should water the lawn using a hose or watering can.

Alternatively, many people opt for weed and feed products, which are easier to time than pre-emergent weed killers.

A weed and feed product is a weed killer combination with lawn fertilizer to kill weeds and simultaneously boost your lawn’s health.

Well, you know, I thought I might need a picture of a lawn someday. Maybe you will - feel free to use this one.

Image by: Flickr/Graham

The best time to apply weed and feed in North Carolina is between the last weeks of March and the first weeks of April.

Applying during very hot conditions will reduce its efficacy. Instead, wait two to four days after mowing the grass to ensure weeds are actively growing. After that, wait a few days before mowing again.

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When you are applying weed and feed, make sure to do so during a period when rain is not around the corner and avoid watering your lawn for between two and four days.

However, your lawn must be damp at the time of application, so do it a day after it has rained, or water your lawn a day before application.

Post-emergent weed and feed treatments are frequently more effective in the fall when weeds are trying to store energy in their roots rather than in the springtime when they have an abundance of it.

They can easily resist the weed killer and additionally benefit from the fertilizer.


Generally, the best strategy is to separate your weed control techniques and lawn fertilization. If it fails, the weeds could be boosted by fertilizer, leaving you with an even bigger problem.

Whichever method you choose, avoid applying weed and feed before applying fertilizer to your grass.

You risk damaging the grass by oversaturating the lawn with fertilizer. Instead, use the weed and feed alone or the fertilizer after a weed-killer treatment.

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