Sheet Mulching is...
...a layered mulch system. It is a simple and underutilized technique for optimizing the benefits of mulch and Nurturing the soil.

Sheet mulching can be used either in establishing landscape, or to enrich existing plantings. In both cases, mulch is applied to bare soil or on top of cut or flattened weeds.

Trees, shrubs, herbaceous perennials and annuals are planted through the mulch, or a small area is left open to accommodate established plants.

Sheet mulch can:

• Suppress weed growth
• Reduce labor and maintenance costs: weeds are composted in place
• Improve nutrient and water retention in the soil
• Encourage favorable soil microbial activity and worms
• Enhance soil structure
• Improve plant vigor and health, often leading to improved resistance to pests and diseases

Step 1: Prepare the site. Knock down or mow existing vegetation so that it lies flat. Remove only woody or bulky plant material. The organic matter left will decay and add nutrients to the soil. Add fertizilers and amendments to this layer if a soil analysis indicates the need. Optional: "jump start" the decay of weeds and grass by adding compost or manure at the rate of about 50 lbs/100 square feet. Soak with water to start the natural process of decomposition. It is much easier to soak the ground now, before the remaining layers of mulch are applied.

Step 2: Plant 5 gallon and larger plants.

Step 3: Add a weed barrier. The next layer is an organic weed barrier that breaks down with time. It is essential that the barrier is permeable to water and air. Do not use plastic. Recycled cardboard, a thick layer of newspaper, or old carpets of natural fiber work well. Many paper companies offer recycled cardboard or paper in rolls of varying widths. Two or three layers may be required to achieve an adequate thickness. But, if the weed barrier is applied too thickly, the soil can become anaerobic. Overlap pieces 6-8 inches to completely cover the ground without any breaks, except where there are established plants you want to save. Leave a generous opening for air circulation around the root crown. Wet down the cardboard or paper barrier to keep it in place.

Step 4: Layer compost and mulch. The top layer mimics the newly fallen organic matter of the forest. Good materials for this layer include chipped plant debris, tree prunings, leaves or straw. They must be free of weed seeds. Well decomposed, weed-free compost is also a good material but it should be spread directly over the weed barrier and covered with bulkier materials such as chipped tree prunings, to optimize weed control. In total, the
compost/mulch layer should be 2-5 inches deep. Many materials suitable for the top layer often have an attractive appearance, making sheet mulch a versatile practice.

Step 5: Plant. Punch a hole in the cardboard and place plants in the soil under the sheet mulch. Smaller plants can often be planted right into the mulch/compost layer. Add a small amount of compost around the rootball if compost has not been included in the top layer.

In most cases, the benefits of sheet mulching outweigh the costs. However, take care to prevent these potential problems:

• As with any mulch, do not pile materials up against the trunks or stems of plants to prevent disease.
• Especially during the dry season, small seedlings will need protection from snails and slugs that will seek cover under the mulch.
• Protect young trees from rodents with physical guards.

NOTE: You’ll find sources of recycled cardboard, recycled mulch and compost here.

ADAPTED FROM: C.R. ELEVITCH AND K.M. WILKINSON, SHEET MULCHING: GREATER PLANT AND SOIL HEALTH FOR LESS WORK, PERMANENT AGRICULTURE RESOURCES AND GEOFF HALL, SHEET MULCH, SENTIENT LANDSCAPE, INC.

Sample Sheet Mulching Specification 3.08 SHEET MULCHING A. After the 5 gallon and larger plant materials have been planted the “sheet mulch” shall be installed. B. Refer to sheet mulch application detail. C. Apply a minimum of two layers of 100% recycled B flute cardboard as a bio-degradable weed barrier to the entire planting area, completely covering all existing soil and vegetation. Wet cardboard while applying to prevent it from blowing away. Sheets of cardboard shall overlap a minimum of 8". Cardboard shall abut directly against edge of pavement, curbs and boulders. Cardboard shall be applied to the edge of installed plant root balls without covering any part of the top of the root ball / root crown area. Excess cardboard shall be folded under itself when abutting against hardscape objects or root crown areas, as opposed to being cut, to avoid excessive cardboard scraps. This folding under process is greatly aided when the cardboard is wet. All cardboard scraps shall remain separated from other construction debris and shall be deposited at a local recycling facility. D. Apply compost and mulch. Apply 1-2" of organic compost on top of the cardboard layer in all planting areas. Reduce organic compost application to 1/2" when 6" or less from the edge of curb. Apply 1-2" of plant debris mulch on top of the compost in all planting areas to protect compost during the planting of 1 gallon and 4" pots and the laying out of drip lines. Keep root crowns of all plants clear of compost, mulch.

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