Step-by-Step Guide to Smothering Grass for New Plantings

Starting a new garden or planting bed often requires clearing existing grass and weeds to create an optimal environment for your chosen plants. One of the most effective and eco-friendly methods to clear grass without resorting to harsh chemicals or extensive physical labor is smothering, also known as sheet mulching or lasagna gardening. This technique involves covering the grass with layers of organic materials that block sunlight, depriving the grass of energy and eventually killing it. The result is nutrient-rich soil ready for planting.

In this comprehensive step-by-step guide, you’ll learn how to smother grass effectively for new plantings, the materials needed, timing considerations, and tips for success.

Why Smother Grass?

Before diving into the process, it’s helpful to understand why smothering is a preferred method:

Environmentally Friendly: Avoids chemical herbicides that can harm beneficial insects, soil life, and water sources.
Improves Soil Health: As the organic layers break down, they enrich the soil with nutrients.
Suppresses Weeds: Smothering not only kills grass but also prevents weed seeds from germinating.
Low Effort: Requires less physical labor compared to digging or tilling the entire area.
Promotes Beneficial Microorganisms: Encourages a healthy soil ecosystem that supports plant growth.

Materials Needed

Here’s a list of materials you’ll need to successfully smother grass:

Cardboard or Newspaper: Provides a biodegradable barrier that blocks sunlight.
Organic Mulch: Such as straw, wood chips, leaves, or compost to add nutrients and further suppress weeds.
Water Source: To moisten layers and help materials start decomposing.
Gloves and Garden Tools: For handling materials and preparing the area.
Optional: Fertilizer or Compost: To boost soil fertility if desired.

Step 1: Plan Your Project

Choose the Location

Select the area where you want new plantings. It could be a vegetable garden bed, flower border, or shrub area.

Assess Grass Type and Density

Thick, established grass may require more time and layers to smother effectively. Thin grass might be easier to kill.

Timing Matters

The best time to start smothering is in early spring or early fall. Cooler temperatures and moisture will speed up decomposition.

Step 2: Mow the Grass Short

Before layering materials:

Mow the grass as short as possible. This reduces bulk and makes smothering more effective.
Remove any large clippings or debris from the surface.

Mowing helps create a flatter surface for laying your first barrier layer.

Step 3: Water the Grass Thoroughly

Watering before laying down barriers softens the grass roots and soil, helping materials settle better. It also initiates microbial activity that aids decomposition.

Step 4: Lay Down the Base Layer – Cardboard or Newspaper

Cardboard vs. Newspaper

Cardboard: Use plain brown cardboard without colored inks or tape. Remove any plastic packing tape or labels.
Newspaper: Use several newspaper sheets (about 8–10). Avoid glossy magazine pages as they don’t decompose well.

How to Lay It Down

Overlap edges generously by at least 6 inches to prevent light gaps where grass can grow through.
Cover every bit of grass completely.
Flatten out wrinkles so it lies snugly against the ground.

This layer blocks sunlight and begins starving the grass below. Over time, it breaks down into organic matter.

Step 5: Wet Down the Barrier Layer

Once your cardboard or newspaper is in place:

Water it thoroughly until it’s damp throughout.
This encourages microbial activity that accelerates decomposition.

Keep this layer moist in the following weeks if rain is scarce.

Step 6: Add Organic Mulch Layers

On top of the cardboard/newspaper barrier, add multiple layers of organic matter:

Materials You Can Use:

Straw or hay
Wood chips or bark mulch (avoid fresh wood chips near beds where nitrogen depletion concerns exist)
Leaves (shredded if possible)
Compost (finished compost works best)

Layer Thickness:

Aim for at least 4–6 inches of mulch on top of your barrier layer. This thickness blocks light further and retains moisture.

If using compost directly as a top layer, keep it thinner (2–3 inches) because too thick a compost layer can become anaerobic (oxygen-poor).

Benefits of Organic Mulch:

Helps retain moisture
Adds nutrients as it breaks down
Keeps temperatures consistent for soil microbes
Further inhibits weed growth

Step 7: Maintain Moisture Levels

For successful smothering:

Keep your mulch moist but not soggy.
Water during dry spells to keep microbes active in breaking down layers below.

This step is crucial because dry layers slow decomposition and reduce effectiveness in killing grass.

Step 8: Wait Patiently – Allow Time for Grass to Die

Smothering is not instantaneous. It takes time for all layers to work effectively:

Expect at least 2–3 months before planting new vegetation.
In cooler climates or with dense grass, it may take longer (up to 6 months).

You will notice after a few weeks that grass turns yellow and dies off underneath.

Step 9: Prepare for Planting

After sufficient time has passed:

Check Soil Condition

Remove any remaining large pieces of cardboard that haven’t broken down fully.

Loosen soil lightly if compacted but avoid deep tilling which can bring weed seeds back up.

Add Additional Compost or Amendments

If desired, spread extra compost or fertilizer on top before planting to boost fertility further.

Step 10: Start Planting Your New Garden

You can now plant directly into your enriched soil bed:

Dig holes through mulch layers.
Transplant seedlings or sow seeds according to plant requirements.

The existing mulch will continue decomposing around roots providing ongoing nutrients and moisture retention.

Tips for Success

Remove Persistent Weeds Beforehand: If you notice deep-rooted weeds like bindweed or Bermuda grass, pull them manually before starting smothering.
Avoid Plastic Sheet Barriers: Plastic blocks water flow and oxygen exchange harming soil life; stick with biodegradable layers like cardboard/newspaper.
Replenish Mulch Annually: Top up mulch yearly to maintain weed suppression and build healthy soil structure.
Consider Companion Plantings: Use cover crops like clover after initial clearing to add nitrogen and improve soil texture before main plantings.

Common Mistakes to Avoid

Not Overlapping Barrier Layers Properly: Light gaps let grass survive.
Using Glossy Paper/Plastic Coated Cardboard: These don’t break down well and may introduce toxins.
Starting Plantings Too Soon: Planting before grass fully dies results in competition for resources.
Neglecting Water Needs: Dry layers hinder decomposition; keep moist especially in dry climates.
Using Fresh Wood Chips Directly On Soil Without Nitrogen Source: May cause nitrogen drawdown affecting new plants’ growth unless balanced with fertilizer/compost.

Conclusion

Smothering grass offers a sustainable way to prepare planting areas without chemicals while enhancing soil health. By following these detailed steps — mowing, layering cardboard/newspaper, adding organic mulch, maintaining moisture, and waiting patiently — you can transform grassy patches into thriving gardens filled with vegetables, flowers, shrubs, or trees.

Patience is key during this process; however, the payoff includes improved soil structure, fewer weeds, reduced maintenance needs, and healthier plants over time. Whether gardening in urban backyards or larger landscaping projects, smothering is an accessible technique worth adopting for greener growing success.