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Killing the Lawn - By Sheet Mulching

January 02 2010 | Ocean Friendly Gardens,
by Paul Herzog

No Chemicals - We strongly recommend removing grass manually and not use any chemicals (herbicides). Studies are showing that these chemicals cause harmful effects to ourselves and the rest of the ecosystem (studies: Non-GMO Report, Environmental Health Perspectives Newsletter). We will provide info on both removing your lawn and also smothering it so it breaks down in place (aka "sheet mulching"). Determine Your Type of Turf Grass There are two types of turf grass and thus different kill approaches:

  • Cool season - Marathon, etc. They stay greener in the winter and produce seed above ground.
  • Warm season - Bermuda, St. Augustine, Zoyzla, etc. They go dormant (brown) in the winter and produces seed below and at ground through runners.

Technique (from the folks at G3/The Green Gardens Group):

Cool season turf grass - Since the seed is produced above ground, just mow it to a short height.

Warm season turf grass - Since the seed is produced below ground (likes little "nuts," right on the roots) or sends out runners at ground level, make sure to remove all the roots and throw them away. (Shake off the soil so you don't remove any unnecessarily and keep it on site.) With grasses like nut grass, the nuts WILL sprout back.

Note: to make it easy to work with soil, to awaken any existing soil biology, and to provide water for new biology you apply, consider thoroughly watering the soil the night before sheet mulching.

  • Compaction test - You can do a compaction test but filling a hole with water, then letting it drain. Fill again and if it doesn't drain a few inches in a 1/2 hour, you need to loosen the soil.
  • Lossen the soil - you want good air and water flow to support soil biology. Use a spade. If you have cool season turf, you can use a spade or an aerating tool.
  • Apply good quality compost, compost tea or worm castings to spark soil biology activity. this will stimulate any microbes asleep in the soil to wake up and "smell the compost." The soil biology will help to eat up any roots your missed. Water thoroughly.
  • Cover with paper - either a roll of painters-type paper or newspaper - to prevent sunlight from sparking regrowth of the grass. Water thoroughly. You can purchase rolls of "Builder's Paper" at hardware stores, e.g., 3 feet x 140 feet for about $11-$13.
  • Cover with mulch - Layer 4" - 6" of fresh tree trimmings, dry leaves or other mulch material. Wet them thoroughly, wetting down the mulch as you go, e.g., applying an inch of it, then moistening it. (Source of mulch - call a tree trimmer to see if they can dump some at your house after their next job.)

Timeframe Until Planting - This recipe assumes you are planting vegetables in a raised bed area (bacteria-based microbes go to work quickly and support grassy, weedy things like veggies). If you are planting perennials, shrubs, etc., then it's best that the sheet mulching "cooks" from a couple weeks to a couple of months before moving forward (fungal-based guys go to work to support the woody plants). Most of the "literature" from veggie gardeners says "go ahead and plant right away" since the veggies are SO bacterially based & they don't need the heavy nutrient stuff created by the breaking down of more celluose items like wood chips or mulch. If the compost is salty (which it may be if it contains horse manure), then they may get tip-burning. Applications of compost tea may remedy this -- steady watering, too. THAT SAID, if you don't have time for the sheet mulch to break down before planting perennials, go ahead and plant directly into it.

Watch the Bay Friendly Gardens Program's video on how to sheet mulch:

 

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