Preen Before or After Mulch: Which is Best for Your Garden?

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Everyone knows what mulch is, but how many of you are familiar with the product Preen?

How Does Preen Work?

Preen is a pre-emergent weed preventer. That means it doesn’t kill weeds that are already growing. Instead, it creates a weed-prevention barrier in the top layer of soil and mulch, helping to stop weed seeds from sprouting in the first place.

Is Preen Worth It?

A resounding yes! If you’re like me, you get tired of constantly pulling weeds from your garden beds. I’m only willing to do so much hand weeding—so anything that helps reduce the effort is welcome.

Mulch is your first line of defense. It helps suppress weeds by blocking sunlight, and it also retains soil moisture and adds organic matter as it breaks down. To make it even more effective, pair it with Preen. Together, they form a powerful combination for keeping beds weed-free.

Tips for Reducing Weed Growth in Your Landscape Beds

Here’s a simple, step-by-step approach to making the most of mulch and Preen:

1. Rake Your Beds

Start by cleaning up your landscape beds. Use a rake to remove leaves, debris, and leftover weeds. A clean slate makes it easier for mulch and Preen to do their job.

2. Lay Down Wet Newspaper

Before mulching, consider placing a layer of wet newspaper over the soil and around your plants. The paper acts as a natural weed barrier, breaks down over time, and works alongside mulch and Preen to prevent weed growth.

3. Apply Mulch

Next, add a fresh layer of mulch. Two to three inches is ideal—any more and you’re just wasting product and money. Mulch not only discourages weeds, but it also helps maintain soil temperature, reduces moisture evaporation, and gives your garden a polished look. Whether you choose hardwood, pine, cedar, pine needles, or wood chips, the key is consistency and coverage.

4. Use Preen Properly

After mulching, sprinkle Preen on top. This creates the weed barrier you’re after. Always read and follow the label instructions. It’s especially helpful to apply Preen early in the growing season, and then reapply about three months later to stay ahead of later-season weeds. Keep in mind: Preen won’t kill existing weeds, and it won’t affect shallow-rooted perennials or bulbs.

Once Preen is applied, avoid heavy foot traffic or digging in your beds, which can break the barrier and allow weeds to grow through.

With a little prep and the right products, you can spend less time weeding and more time enjoying your garden.

Visit The Great Big Greenhouse Garden Center in Richmond for mulch and Preen, and get expert tips to simplify your yard work this season.

HAPPY MARCH GARDENING!!!!!

24 thoughts on “Preen Before or After Mulch: Which is Best for Your Garden?”

  1. Thank you — LOVING these ‘calendar reminders’ of what the heck we’re supposed to do in the garden. By the time I usually think about Preen — weeds are up and we’re fully into Spring. Please keep doing this! :) HUGELY helpful.

  2. What is better to lay over the dirt before the mulch is laid down… plastic or “weed felt” (more open weave)?

    • Lyn,
      Good Morning. Definitely use a weed fabric and not any plastic. The fabric will allow moisture through and at the same time keep weeds from penetrating through. Doug

  3. I see it says Preen will not harm shallow rooted perenials or bulbs, but specifically, what about hibiscus? We cut ours off at ground level in the fall, and they have come back for a few years. Right now, they have not sprouted up yet, but we are trying to prevent the weeding this year.

    • Harry,
      Good Morning.
      You are safe. Preen is safe to use around our hardy, herbaceous perennials, such as the hibiscus. Preen keeps “seeds” from germinating and growing. The soil is still a little chilly for our hardy hibiscus to start growing. Thank you for taking the time to send us your gardening question. Doug

  5. I have several established perennial beds with mixed spring, summer and fall plants. Should I apply preen BEFORE they start coming up (right now in early spring – blank slate with no plants yet emerging) or wait until plants start to emerge and have grown a few inches and then apply AROUND the plants? Thank you!

    • Kathy,
      Good Afternoon. Preen should not affect your perennials from coming and up and growing. Preen can be used in many garden beds such as around herbs, vegetables, and perennials. Once you put Preen down then you want to try not to walk through these gardens. Walking can break the barrier that Preen creates. Doug

    • John,
      Thank you for this question. Actually, putting Preen down first is more effective in keeping weeds from growing then it is to put Preen on top of the mulch. Or, if you really want the best protection then you may want to think of doing both underneath and on top. Doug

  7. I did not put Preen down….lots of weeds now, early June in North East Zone 6. Can I still Preen after I weed well for new growth? What do you suggest?
    Thanks

    • Lynn,
      Weeds are constantly growing, flowering, and dropping seeds. So, yes, Preen cam help reduce / eliminate future weeds from germinating and growing. Good luck, Doug

  8. I live in Savannah Ga and weeds start sprouting early. We rarely have a hard, prolonged frost. I never know when to start applying Preen

    • Sherry,
      Good Morning. We both know that Savannah is in a warmer climate than here in Richmond. With this said then I would think about putting Preen down in late January or around the first of February. Preen stays active for around three months. So, for you in Savannah earlier the better chance of keeping the early sprouting weeds from germinating. Then I would consider putting down a second application of Preen in two to three months. Good luck. I love Savannah. Doug

    • Pam,
      Good Morning.
      I think you will need to purchase the products separately. I am not aware of any product that you can buy that has mulch and Preen already together. Doug

    • Thank you.
      I had no idea that Preen has wood chips. Up to this point we have not carried the wood chips in our inventory. Thank you for this information. Doug

  11. THe pumpkins that I planted from seed died after I applied preen and mulch, they weren’t up very far when I applied the preen. Now I have looked for a cause to the loss of the plants and can’t see any guidelines on the preen sheet for pumpkins. Do you think it could have caused the loss of the plants?

    • Pat,
      Good Afternoon.
      Sorry to read about you losing your pumpkin plants. To my knowledge Preen should not be the culprit since you mention that the pumpkins had already started growing. But, I can’t say 100%. I just don’t know what would have caused all your pumpkin plants to die. I hope that somehow you can solve this mystery. Doug

  12. We just planted 2 beautiful David Austin rose gardens as well as some hydrangeas and vinca flowers. My husband put Preen down before putting down about 2 inches of good black mulch and then he sprinkled Preen on top of the mulch also. Is that too much Preen? Will it be harmful? Is Preen ok for shrub roses? Really want to know because we have 60 shrub roses and they were expensive so don’t want them to die! Please reply.

    • Linda,
      Good Morning.
      You are good with using Preen under as well as on top of the mulch. Preen is safe to use in and around shrubs. Preen is keeping weed seeds from germinating and not hurting established shrubs or trees. Thank you for this message. Take care, Doug

  13. I use Preen in the fall, in the early spring and before planting seeds. How does it keep weeds from growing but my flower seeds still germinate??

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