How To Use And When To Apply Preen Garden Weed Preventer

Without a doubt, one of the biggest hurdles any gardener faces is what seems to be a never-ending battle with weeds.

Regardless of how often they go outside and weed with either a tiller or by hand, the dreaded nuisances continue to make their appearance throughout the growing season.

Quick Answer:

To use Preen, first, remove existing weeds. Sprinkle Preen granules evenly over your garden surface and water immediately to activate it. Apply in the early growing season before weed germination, and reapply every 9-12 weeks. Remember, Preen prevents weeds – it won’t kill existing ones. Always follow label instructions.

One simple way to lessen the battle with weeds in the garden or flowerbeds is to apply a weed preventer such as Preen.

What is Preen Weed Control?

Preen Garden Weed Preventer - 13 lb. - Covers 2,080 sq. ft.
  • Stop weeds before they start for up to 3 months guaranteed
  • Safe for use around over 200 established flowers, vegetables, trees and shrubs
  • Apply anytime in spring, summer or fall
  • Not for use on lawns

Preen Weed Preventer is a granular garden product formulated to be shaken or broadcast across the soil surface to reduce weed problems. Once activated, it stops weeds from germinating in your flowerbeds, gardens, and around trees and shrubs.

The original formula does not kill existing weeds but instead prevents weed seeds in the soil from germinating and pushing through the soil surface.

How Does Preen Work?

Preen is a type of herbicide classified as a pre-emergent, formulated to work to control annual grasses and certain broadleaf weeds.

The active ingredient in Preen is trifluralin, one of the most commonly used herbicides in agricultural production and gardening. Trifluralin’s mode of action is as a mitotic inhibitor. It stops mitosis, or cell division, in rapidly dividing cells, such as germination and root formation. The microtubules that pull the cells apart are disrupted, halting division.

In order to be activated, Preen weed preventer needs to be watered into the soil.

Once activated and in the soil, the product creates a barrier within the top couple of inches that prevents weed seeds from germinating. Over time, the active ingredient will degrade, making it necessary to reapply throughout the growing season for the best results.

When To Apply Preen

When applied correctly, Preen can save you a lot of time and effort by reducing the need for manual weeding.

Early Spring

The best time to apply Preen weed preventer is in early spring, just before the growing season begins. This will help to prevent weed seeds from germinating and taking root in your garden.

Late Spring

If you missed the early spring application, don’t worry. You can still apply Preen weed preventer in late spring when the soil has warmed up, and the weeds are starting to grow.

Early Summer

If you didn’t apply Preen weed preventer in the spring, you can still apply it in early summer. This will help to prevent new weeds from growing while also killing any existing weeds that have already taken root.


You can also apply Preen weed preventer in the fall to prevent winter weeds from taking root. This will help to keep your garden weed-free throughout the winter months and into the following spring.

*It’s important to note that Preen weed preventer should not be used on flower seeds, and it should not be used in areas near ponds, lakes, waterways, or other bodies of water.

Benefits of using Preen in Your Garden

There are many benefits to using Preen in your flowerbeds and garden plots.

Simply reducing the number of weeds in an applied area make it a favored product for home gardeners, but many people overlook the trickle-down effect it has.

  • Easy to use; most containers come with a specially designed cap to help evenly broadcast product across the soil with just a simple shake of your wrist.
  • Weed seeds never germinate, drastically reducing the number of weeds you have to contend with.
  • Garden plots and flowerbeds look pristine with minimal effort.
  • Using Preen as a weed-preventer is more effective than hand weeding. When hand weeding, it’s challenging to remove the entire weed, so it often comes back with a vengeance; Preen stops weeds entirely.
  • There is little need for post-emergent herbicides applications if used properly. This cuts down on the cost associated with purchasing weed killers, as well as the safety concern regarding their application.
  • With fewer weeds growing in unwanted spaces, your vegetables, ornamental flowers, trees, and shrubs are not competing for resources such as water, sunlight, and soil nutrients. Your plants will grow stronger, healthier, and have higher yields.
  • Less time is spent pulling or digging up weeds in your garden and/or flowerbeds. This means more time to sit outside and relax, enjoying the weather and gardens you are growing.
  • Weeding can be extremely taxing on your body. Applying a pre-emergent product to prevent weeds reduces the fatigue on your body, saving your hands, knees, and back from hurting for days to come.

Tips for Use

As with any other garden product, especially a chemically active one, some tips and warnings should be followed to ensure safety and increase the product’s efficiency.

  • Preen can be applied in the spring as soon as soil temperatures begin to warm up and perennial plants start growing. Early application will get a jump start on weed prevention.
  • Avoid applying the product to areas in the garden or flowerbeds where you intend to plant seeds or transplant seedlings or young plants.
  • Wait until newly planted transplants have been watered a couple of times before application. This ensures the plants are acclimated enough to tolerate the product if they come in contact with it.
  • Avoid getting Preen on the leaves if possible to prevent damage to the foliage; apply when the plants are dry to prevent the product from sticking to them.
  • Follow the label directions for the application rate. Good coverage equates to effectiveness.
  • After application, water just enough to wet the soil surface to activate the soil barrier.
  • Reapply product every 9 to 12 weeks for continued prevention. In areas where you receive a higher amount of rainfall or you have very sandy soil, you may need to reapply more frequently.
  • Try to minimize soil disturbance after application and activation, as this decreases the effectiveness of the “barrier” created in the soil.


Fighting the battle against weeds in your flowerbeds and garden is considerably simpler when you add Preen to your arsenal.

Preen is a weed preventative, also known as a pre-emergent herbicide, that creates a barrier in the upper soil surface and prevents weed seeds from germinating.

Stopping them before they can even sprout cuts down on the time and energy spent weeding and encourages stronger, healthier growth in your plants.

Preen Garden Weed Preventer - 13 lb. - Covers 2,080 sq. ft.
  • Stop weeds before they start for up to 3 months guaranteed
  • Safe for use around over 200 established flowers, vegetables, trees and shrubs
  • Apply anytime in spring, summer or fall
  • Not for use on lawns

Last update on 2024-05-30 / Affiliate links / Somes Images and Data from Amazon Product Advertising API