How To Use Pre-emergent Herbicide For Vegetable Gardens

One of the best ways to keep weeds out of your vegetable garden is to use pre-emergent weed control.

When used correctly, pre-emergent prevents weed seeds from developing into plants. And this means less weeding for you to do by hand.

But you have to be careful when using pre-emergent herbicide for vegetable gardens. Not every product is suitable for use around edible plants. And when used in the wrong way, pre-emergent can prevent or harm your vegetable plants as well.

So in this article, we take a look at how to use your pre-emergent safely and effectively so you can get the best results.

Let’s dive in!

Before You Start

Pre-emergent herbicide prevents weed seeds from developing after germination. But it doesn’t kill weeds with established root systems.

So, before you apply pre-emergent to your vegetable garden, it’s a good idea to remove any weeds that are already growing. You can pull them out by hand or dig them out using a garden tool.

Choosing A Pre-emergent Herbicide

Not all types of pre-emergent herbicides can be used the same. Most of them are not recommended for use around edible vegetables and fruits. Instead, they are designed for use on lawns and around trees, shrubs, and flowers that won’t be consumed.

The safest pre-emergent for use around vegetables is trifluralin. You can find it in the popular brand Preen.


Trifluralin is a chemical pre-emergent for controlling a wide range of broadleaf weeds and grassy weeds. Trifluralin is often used in agriculture because you can use it to stop weeds growing around vegetable, fruit, and nut crops.

You still have to be careful when applying trifluralin. Because it not only stops weeds from growing. If you apply pore-emergent at the same time as you plant vegetable seeds, then it can stop them from emerging as well.

But trifluralin breaks down over time. And its suppressive effects have usually completely gone within a few months. And you can expect each application to give you 4-6 weeks of good weed control.

Before using trifluralin in your vegetable garden, check the product label to ensure you can use it on the type of vegetables being grown. Don’t use trifluralin around chard, lettuce, beats, and corn.

Corn Gluten Meal

An organic and natural alternative to chemical pre-emergents is corn gluten meal. It raises the protein content of the soil to a level that inhibits the weed seeds from developing roots.

But corn gluten meal is not as effective as trifluralin. And you can expect that some weeds will still grow.

You can apply corn gluten meal to the soil around established vegetables, fruits, herbs, and landscape beds. And corn gluten meal has the added benefit of containing 10% nitrogen. So it fertilizes your plants as well.

Applying The Pre-emergent In Your Vegetable Garden

Firstly, read the instructions on the pre-emergent herbicide that you choose to buy. Although the process of using pre-emergent for vegetable gardens is very similar across all products, some may have special instructions to follow.

Wait until the vegetable plants have grown to around 3 to 5 inches high before you put the pre-emergent herbicide down. Some pre-emergent herbicides can kill young plants.

Carefully measure out the required amount of pre-emergent according to the instructions that come with the product. And then spread the herbicide evenly over the surface of your vegetable garden.

If your product is granular, use a rake to mix it into the top 1-2 inches of soil.

After you’ve applied it, you need to water pre-emergent herbicide. Water activates the pre-emergent. And allows the pre-emergent to soak into the soil, forming a chemical barrier for weed prevention.

You can water the pre-emergent yourself or allow rainfall to do the job. But, if you’re using trifluralin, you should water the pre-emergent granules into the soil immediately after application. Trifluralin breaks down quickly when exposed to sunlight and loses its potency.

Repeat the pre-emergent treatment as recommended by the product instructions. This will prevent weeds from appearing throughout the growing season.

What Else Can You Do?

Other good practices that can help to prevent weeds in your vegetable garden are:

Mulching – applying a 4-6 inch layer of mulch around your vegetable plants can prevent weed seeds from germinating in the soil. And make it harder for the seeds to land in the soil in the first place.

Watering – be careful when you water your vegetable plants. Try to only water desirable plants and not the empty areas around them. This reduces the amount of water that weeds can access.

Cultivation – use a garden hoe to cultivate the soil in the rows between your vegetable plants to keep the weeds away.

Leave a Comment