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Weed Suppression:
Landscape Fabric?

I was working at a site that had been overrun by weeds. They completely invaded the landscape beds. And yet, those very beds had a weed suppressing landscape fabric installed. Seeing the absolute mess and the management strategies that led to it has motivated me to share some pros & cons about the use of landscape fabric.

Should you use landscape fabric? What causes it to fail? Are there any alternatives to a synthetic weed barrier? What should be considered as a long term solution?

Landscape or weed fabrics create an impassible barrier that stops the upwards growth of plants from underneath. So the soft stems and leaves get trapped beneath. For this barrier to work properly though, an application of mulch is needed. This helps to hold the fabric in place, blocking out the sunlight and suppressing growth. As a short term solution for reclaiming a weedy bed, the fabric can help you out.

DISADVANTAGES OF LANDSCAPE FABRIC:

Synthetic weed barriers can accomplish a task, but they are no silver bullet. Their limitations might not become apparent until a year or two has passed. But before long, you may start to see that your beds are just as weedy as they were before, especially if they've been neglected.

Wood based mulches are customarily applied on top of these barriers. But their biodegradable nature causes them to slowly break down, forming a layer of soil. That upper layer can be a perfect rooting medium for fresh weed seeds that find their way into your beds. Before you know it, you've circumvented your weed barrier and weeds just grow right on top of it.

All the while the microbial processes that rejuvenate your soil are being hindered by this synthetic, barrier. Earthworms and various arthropods cannot freely pass from below the soil up to the surface.

Your perennial plants become girdled as they grow wider and wider. Clumping and rhizomatous plants get trapped underneath. And creeping or layering plants cannot properly root as their roots get entangled in the fabric.

Video: Landscape Fabric Finding an Alternative

I've been able to reclaim weedy and grass filled beds using cardboard as sheet mulch.

A BIODEGRADABLE ALTERNATIVE:

A free, biodegradable alternative to landscape fabric is to use simple old cardboard. This idea is derived from the concept of sheet mulching. In permaculture, sheet mulching can be done to reclaim an area of land that might have been weedy or even covered with grass.

Cardboard is applied to the area. Then a layer of mulch goes on top of that. In creating a highly fertile site, a gardener may put several layers of materials. Leaves, compost, grass clippings, straw, etc. But in more conventional landscape applications, it would certainly work to just put a wood based mulch right on top of a couple layers of cardboard.

Weeds or grasses will be unable to pass up through the cardboard. With the inclusion of mulch you can effectively smother these unwanted plants, making way for new plantings. But meanwhile, that cardboard will be eaten up by earthworms and won't interfere with biological processes.

Smothering Weeds with Sheet Mulch of Cardboard and Wood Chips
This patch of weeds was suppressed with simple cardboard and mulch! pin it


TIPS FOR SUCCESS:

USE A THICK LAYER: Some people mention using newspaper as an option. For maximum effectiveness, you would need multiple layers and a substantial mulch application placed on top. I prefer card board, using 2 layers (standard thickness). A single layer will work well if it is extra thick.

CARDBOARD PREP: Select the largest pieces you can possibly get. You can often go to local businesses and ask if you can dumpster dive for their cardboard. Pull off any staples, tape or stickers, since these won't decompose. Well established, vigorous plants may send their stems along the bottom, seeking an edge or a hole in your barrier. So when you need to use multiple layers, be sure to generously overlap the seams. It's also a good idea to pull out or dig up weeds that are at the very edge of the bed.

IT'S NOT BULLET PROOF: Worms enjoy soft, decomposing cardboard. Birds enjoy worms. So be aware that you may have animals perforating your sheet mulch layer. This might require weeding out any plants that find their way to the light. Besides pulling out those weedy culprits, you can always apply a quick patch. Just pull away the mulch and drop down a fresh layer of cardboard.

LONG TERM STRATEGY:

Are you looking for a way to reduce mulching requirements? How can you keep out weeds? Nature abhors a vacuum. So your final landscape or garden should be designed in a way that fills those large empty spaces.

Plan out multiple layers of trees, bushes, shrubs and herbal plants. Allow these to fill in your beds, choking out any weeds that make their way into your property. To cover large areas of ground, without relying on grass, consider using ground covers.