You should always kill weeds before mulching your garden beds. A layer of mulch may smother some small weeds, but larger, established weeds will grow up through your mulch. To prevent future weed growth, prepare your garden by killing weeds and installing a layer of landscape fabric before mulching. Although pulling up weeds by hand is a great tactic, there are other ways to kill weeds. You can spray weeds with weed killer, till the soil in your flower bed to destroy weeds, or use a flame weeder.
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What Happens if You Mulch Without Pulling Weeds?
If you spread a layer of mulch over existing weeds, the majority of those weeds will grow up through the mulch and infest your garden. This is because mulch won’t smother weeds that have already gotten a foothold. This rule applies to any type of mulch. You might temporarily cover large weeds with mulch, but those plants will find a way to survive.
- Well-established weeds will survive long enough to grow through a layer of mulch.
- Mature weeds can grow through 3–4 inches (7.5–10 cm) of mulch after being covered.
- If you mulch over existing weeds, you will have to continually attack those weeds as they break through your mulch layer.
Mulching over the top of existing weeds leads to a whack-a-mole scenario where you will have to continue pulling weeds as they break through your layer of mulch. The whole time you’re doing this, the weeds in your garden will continue stealing water and nutrients from your desirable plants.
Does Mulch Stop Weeds?
Mulch is excellent at suppressing weeds that attempt to sprout. So, if you have cleared your garden of visible weeds, any new weed seeds that germinate will be smothered by mulch. This prevents your garden from being invaded by weeds. You just have to clear out large weeds before mulching.
- Mulch will stop new weeds from sprouting in your garden.
- Mulch won’t work if it’s spread on top of already growing weeds.
- Organic and inorganic mulches both work best when spread in a layer 3–4 inches (7.5–10 cm) deep.
Both organic mulch and inorganic mulches are great at smothering weed seedlings. Whether you use bark mulch, nut hulls, straw, shredded leaves, gravel, or rubber, you’ll create an effective weed barrier. Just remember to spread your mulch 3–4 inches (7.5–10 cm) deep in your garden beds for best results.
How to Get Rid of Weeds Before Mulching? [5 Methods]
Before you spread any mulch in your flower beds, start by clearing out weeds. However, there are several methods you can use to get the job done. Here are the best options:
Commercial Weed Killers
In order to kill weeds fast before mulching, spray them with a fast-acting weed killer. Systemic herbicides work when they are absorbed through the leaves of the weed. Then, they travel through the plant’s vascular system. In 1–2 weeks, the plants you spray will be entirely dead. However, you’ll probably see weeds begin to wilt within hours of spraying them.
- Spray weeds with this fast-acting commercial weed killer.
- Commercial herbicides kill weeds systemically, including the roots.
- Shield your flowers and vegetables from weed killer spray by using cardboard sheets as barriers when spraying weeds.
Be careful when using weed killer sprays in your garden. Herbicides that attack weeds also attack desirable plants. If your garden is currently a mix of weeds and garden plants, protect your desirable plants while spraying weed killer. Use cardboard sheets as a shield to prevent weed killer from spraying onto plants you want to keep alive.
Organic Weed Killer
If you wish to keep your garden totally herbicide-free, you can spray actively growing weeds with a weed killer made from citrus oil. Citrus oil is the best natural weed killer on the market. Avoid using vinegar-based “organic” weed killers because vinegar is harmful to bees and other pollinators.
- Use this organic weed killer made with citrus oil as an alternative to herbicides.
- Spray weeds with organic weed killer, then allow 1–2 weeks for the weed to die completely.
- Dead weeds can easily be pulled up or raked out of your garden.
Organic weed killer will attack any plant it’s sprayed on, so it’s essential to shield your garden plants from overspray. However, the organic and commercial weed killers we recommend do not linger in the soil, so you don’t have to worry about ruining your garden.
Till Your Garden Soil
If you are starting a new garden, or revitalizing a garden where annuals are grown, you can destroy existing weeds by tilling your garden. Rent a rototiller from your local hardware store or tool rental company. Then, till the soil to a depth of 6 inches (15 cm). This will destroy weeds and break up their roots. It also creates loose, aerated soil where plants will thrive.
- If there are no desirable plants currently growing in your garden, consider tilling it to kill weeds.
- Rent a rototiller to get the job done quickly and effectively.
- Till the soil to a depth of 6 inches (15 cm) to kill weeds, destroy root systems, and loosen your soil.
- Tilling is not a good option if you have an established garden—it will kill any actively growing plants.
If you choose to till your garden to kill weeds, tilling also gives you a great opportunity to add compost and fertilizer to the soil. Tilling in soil additives will improve your soil quality and drive more plant growth. However, tilling isn’t an option in gardens where you are growing established perennials. Tilling an active garden will destroy the plants growing there.
Use a Flame Weeder
You can quickly kill weeds in a garden by using a flame weeder. A flame weeder is typically fueled by propane. A long wand ends in a head heated by burning propane. Simply pass the flame weeder over weeds in your garden for a couple of seconds. The super-heated air will destroy plant cell walls, killing weeds instantly. In a few days after flame weeding, the weeds will wither and dry up for easy removal.
- Kill weeds quickly with this propane-fueled flame weeder.
- Keep the head of the flame weeder a few inches over the weeds for just a couple of seconds—the heat from the flames will destroy plant cell walls and kill the plant.
- Do not set weeds on fire with a flame weeder.
- Check with your local laws to see if flame weeders are safe to use in your area.
It’s essential that you do not set weeds on fire by using a flame weeder. This is dangerous and unnecessary. The hot air a few inches from the flames is enough to kill weeds. Additionally, do not use a flame weeder during drought or if your local area forbids their use. Flame weeders are super fast and efficient, but they’re not a good choice if you live in an area at risk of wildfire.
Make Hand Weeding Easy
Hand weeding your garden beds to remove weeds may seem like a tough chore, but it is a great way to get rid of weeds. Not only is it entirely organic, but it removes weeds to the root and clears your flower bed instantly. To make life easier, invest in a good hand-weeding tool.
- Simplify hand weeding with this weeder tool.
- Remove weeds with their roots to instantly kill weeds and clear your garden.
- Hand weeding is 100% organic and requires no waiting for weeds to wilt after spray or flame treatment.
When hand weeding, make sure to remove weeds down to the root to keep them from growing back. Once you’re done weeding, you’re ready to begin planting. When you pull up weeds by hand, there’s no need to wait for a chemical spray to take effect and wilt your weeds.
What Should You Do Before Mulching?
Before you spread your fresh mulch, prepare your garden by removing weeds. Next, create a defined border around your garden. A ditch 4 inches wide and 4 inches deep (10 cm by 10 cm) will prevent creeping grasses and weeds from invading your garden. Install a rock garden border to help retain mulch and keep weeds out.
- Remove any existing weeds in your garden.
- Create a garden ditch or rock garden border to keep mulch in and weeds out.
- Lay this landscape fabric over the garden—cut holes to allow desirable plants to grow through the fabric.
- Pour a 4-inch (10 cm) layer of mulch on top of your landscape fabric and spread it evenly.
Finally, lay landscape fabric over your garden soil and secure it in place with landscape staples. Landscape fabric is a water-permeable layer that allows nutrients, water, and oxygen to reach the soil but prevents weeds from sprouting. Simply cut an ‘X’ in the fabric and fold back the flaps to allow existing plants to pass through. Use this same system to plant new garden varieties in the soil. With these steps completed, you’re ready to spread your mulch.
- Heavy-duty and durable for long-lasting weed control.
- Easy for you to install and set up.
- Keeps weeds out without blocking necessary air and water.
Can You Put Mulch Over Weeds?
Do not pour mulch over weeds in your garden bed. If you do, established weeds will sprout through the mulch. In order to clear your garden of weeds before mulching, follow these tips:
- Kill garden weeds with weed killer spray, tilling, flame weeding, or hand-pulling weeds.
- Dig a border separating your garden from your yard, to prevent weeds and grass from creeping in.
- Add a rock garden border to keep mulch from spilling out.
- Spread landscape fabric over your garden to help suppress weeds.
- Pour 3–4 inches (7.5–10 cm) of mulch into your garden to stop weed seeds from sprouting.
Although mulch isn’t effective at smothering mature weeds, it is excellent at stopping new weeds from sprouting. So, as long as you clear the weeds out of your garden before you spread your mulch, your garden will remain weed-free throughout the growing season.