Kill your lawn

Author: Dave Tomashefski

Below are a few common methods for converting lawn to garden beds. These can be used whether you will be planting seeds or plants.

Method 1: Sheet mulching

You can plant almost immediately. Takes lots of cardboard.

When to use it

  • In sun or shade.
  • When grass is actively growing.
  • If starting a garden from seed, use a fine mulch (like leaf compost) and wait a few months until the cardboard has broken down.

Supplies

  • Cardboard or newspaper.
  • Hose and running water.
  • Mulch. Leaf compost is optimal: it’s loose and light, which means it’s easy for ground-nesting bees to move aside.
  • (Optional) A manual or mechanical bed edger can be used to create a well-defined border.

Instructions

  • Mow grass (optional, but makes it easier to cover grass where cardboard overlaps).
  • Use bed edger to define border, if desired.
  • Cover with layer of unwaxed cardboard or, alternatively, newspaper > 10 sheets thick.
  • Wet the cardboard or newspaper.
  • Cover with approximately 4” of mulch.
  • When desired, cut holes in cardboard to plant plants. Leave a 2” gap between the mulch and the base of the plant to avoid rot.

Pros

  • Can be planted immediately (unless starting a garden from seed).
  • Can be used in sunny or shady areas
  • No soil disturbance / weed seed stimulation.
  • No soil loss.
  • Uses biodegradable materials.
  • No chemical toxicity.
  • Can be used in sunny or shady areas.

Cons

  • May not kill perennial weeds such as Canada thistle and field bindweed.
  • Requires a lot of cardboard.

Method 2: Smothering

Good use of a tarp. Takes at least 2 months.

When to use it

  • In sun or shade
  • When grass is actively growing.
  • Takes 2 months to kill grass, an entire growing season to kill most perennial weeds (e.g., white clover), and 2 or 3 growing seasons to kill some perennial weeds (e.g., Canada thistle and field bindweed).
  • Be patient if starting a garden from seed. Starting with a completely clean slate is especially important in this case.

Supplies

  • Tarp.
  • Greenhouse repair tape.
  • Stakes or rocks to hold tarp in place.

Instructions

  • Mow area (optional, but may result in less plant debris when tarp is removed).
  • Cover with dark, impermeable tarp, or other material such as plywood. Secure with rocks or stakes.
  • Leave in place for at least 2 months.
  • Promptly patch or mend with tape any holes that develop in the plastic. Greenhouse repair tape works best.

Pros

  • Can be used in sunny or shady areas.
  • No soil disturbance / weed seed stimulation.
  • No soil loss.
  • No chemical toxicity.

Cons

  • Takes a long time to kill some perennial weeds such as Canada thistle and field bindweed.
  • Tarp is non-biodegradable.

Method 3: Solarization

Kills deep weed seeds in full sun. Takes time, setup is labor intensive.

When to use it

  • Full sun areas, i.e. areas receiving at least 6 hours of direct sunlight per day.
  • For 2-4 months, which must include July and August (i.e., the hottest months of the year).
  • Be patient if starting a garden from seed. Starting with a completely clean slate is especially important in this case.

Supplies

  • Lawnmower
  • Hose and running water
  • Clear, UV resistant plastic sheeting, 4 or 6 mil thickness. (can be bought from Home Depot).
  • Greenhouse repair tape. 3M brand clear repair tape sold at Home Depot.
  • Shovel for burying edges of plastic. A flat-edged shovel works best.

Instructions

  • Remove sticks, rocks, and debris from area.
  • Mow grass very short.
  • Optional: rototilling may increase effectiveness of solarization.
  • Thoroughly wet area.
  • On following day, cover with sheet of clear plastic. Recommended plastic thickness is 4 or 6 mil.
  • Plastic should not be loose or wrinkled.
  • Secure plastic around perimeter of area by burying edges at least 4” deep.
  • Promptly mend any holes in plastic, preferably within 24 hours. Use greenhouse repair tape.

Pros

  • Kills weed seeds in top 2 – 6” of soil.
  • No chemical toxicity.
  • No soil loss.

Cons

  • Only works in sunny areas.
  • May not be effective on weeds with roots extending deeper than 2-6”.
  • Creates plastic waste.

Method 4: Rototilling

Quick results in turf with low weed pressure.

When to use it

  • Flat areas (sloping areas are susceptible to erosion).
  • Soils that are not overly rocky.
  • When grass / weeds are actively growing. This will allow assessment of new weed germination post-rototilling.
  • Be patient if starting a garden from seed. Starting with a completely clean slate is especially important in this case.

Supplies

  • Lawn mower.
  • Hose and running water.
  • Rear-tine rototiller (this is a heavy duty rototiller suitable for grass removal).
  • Rake
  • Hoe
  • (Optional) A manual or mechanical bed edger can be used to create a well-defined border.

Instructions

  • Mow very short.
  • Clear area of sticks, rocks, and other debris.
  • Thoroughly water the area and let the water soak in / dry for 24 h. The target soil consistency is soft and crumbly but not muddy.
  • Till to a depth of approximately 6” using a rear-tine rototiller. Make sure soil is thoroughly churned and all clods and grass clumps are broken up.
  • Use bed edger to define border, if desired
  • Rake up and remove exposed plant roots.
  • Wait 2 weeks to assess weed germination. Remove newly germinated weeds with hoe or by hand. Repeat as necessary until weed germination subsides.

Pros

  • No soil loss (assuming no erosion).
  • Equally effective in sun and shade.
  • Little waiting, depending on extent of weed germination.
  • No chemical toxicity.
  • No plastic waste.

Cons

  • Exposure of bare soil stimulates weed germination.
  • Weeds with roots extending deeper than 6” will likely re-sprout.
  • May cause erosion on sloping land.

Method 5: Sod-cutter

Quick results in turf with low weed pressure. Lose precious soil.

When to use it

  • Soils that are not overly rocky.
  • When grass / weeds are actively growing. This will allow assessment of new weed germination post sod-cutting.
  • Be patient if starting a garden from seed. Starting with a completely clean slate is especially important in this case.

Supplies

  • Lawnmower
  • Hose and running water.
  • Sod-cutter.
  • (Optional) A manual or mechanical bed edger can be used to create a well-defined border.

Instructions

  • Mow area very short. This will make it easier to roll up / move the cut sod.
  • Thoroughly water lawn. Allow to soak in / dry for 1-3 days.
  • Operate sod-cutter at appropriate depth. Grass as well as roots should be removed. The most common depth is 1.5”.
  • Roll up and remove the sod strips, exposing the bare soil underneath.
  • Use bed edger to define border, if desired.
  • Wait 2 weeks to assess weed germination. Remove newly germinated weeds with hoe or by hand. Repeat as necessary until weed germination subsides.

Pros

  • Equally effective in sun or shade.
  • Little waiting, depending on extent of weed germination.
  • No chemical toxicity.
  • No plastic waste.

Cons

  • Topsoil loss.
  • Will not kill weeds whose roots are deeper than operating depth, e.g., 1.5”.
  • Exposure of fresh, bare soil may stimulate germination of weed seeds.

Method 6: Herbicide

Effective on large areas. Be aware of unintended effects.

When to use it

  • When grass is actively growing.
  • Special consideration is needed near waterways (see note below)
  • Repeat applications may be necessary in areas with heavy weed pressure.

    Supplies

    • Lawnmower.
    • Roundup Ready to Use Weed and Grass Killer with Sure-shot Wand.
      • Note: if applying near a waterway or pond, use AquaNeat and follow instructions on label.
    • Turf Mark Spray Indicator.

    Instructions

    • Mow area.
    • Use 2% glyphosate solution containing surfactant and blue dye. Easiest technique is to use Roundup Ready to Use Weed and Grass Killer with Sure-shot Wand, and add 2 oz. of Turf Mark Spray Indicator (i.e., blue dye) to 1.33 gallon container.
    • For best results, apply on sunny day when temperature is greater than 60 F. Do not apply on windy day due to risk of drift.
    • Thoroughly spray area.
    • Two weeks later, spray one more time.
    • Wait 3 days before planting.
    • Cover dead vegetation with 2” of leaf mulch, if desired.

    Safety

    • Wear eye protection and disposable latex gloves.
    • Wash hands and forearms after use.
    • Keep area free of pets and foot traffic for 4 hours or until herbicide has dried.

    Pros

    • Kills weeds down to the root.
    • Effective in sun or shade.
    • Does not disrupt soil / stimulate weed seed germination.
    • Minimal plastic waste.
    • Minimal waiting.

    Cons

    • The Xerces Society reports that exposure to glyphosate can disrupt bee navigation and impair their gut bacteria, thereby increasing the bees’ susceptibility to pathogens.