SHEET MULCHING - TENDING OVER TIME

Got time on your hands this spring? You might want to get out into the garden and do some sheet mulching.

Sheet Mulching is a process that begins with laying cardboard and mulch over lawn to encourage the turf to die. Layers of other organic components may be added; however, they are not essential. In fact, California natives are adapted to a low nitrogen environment so cardboard doesn’t have to stay in place so long and you don’t have to add manure or compost; it may even be counterproductive to do so.

Sheet mulching can also be used on soil or landscape that is not turf, but for our purposes, we will focus on sheet mulching on top of lawn. It is a very effective method to get rid of lawn, and one that keeps the carbon from the dead lawn in place, to help nourish biologically rich soil.

When the grass roots or rhizomes under the sheet mulch get wet, they start to grow. They begin to search for sunlight, so they can get energy from photosynthesis. Some of them die before they find a way through the cardboard; others die before they get through the mulch. A very few may make it to the top of the sheet mulching, and they can be plucked as soon as they stick their heads above the mulch. This way the grass will truly die instead of just go dormant (look brown because it hasn’t been watered).

· Sheet mulching is the process of using cardboard and 4-6" of mulch to smother any remaining grass rhizomes, generally before they can reach the sun to photosynthesize and get energy to grow again.

· Sheet mulching has about the same effective rate as chemicals like Round Up or sod removal- about 90%.

· With any of these methods of grass removal, there may be some maintenance involved, especially in the first three years after "killing the lawn" to make sure it does not come back. The amount varies from site to site- some places need a lot more maintenance than others, and it's hard to tell beforehand which ones will be more difficult in the long run.

· The key for areas that have been sheet mulched, is to pull any grass out from the depth of its rhizome (root) as soon as it pops its head out of the mulch. This is much less labor intensive than waiting until it grows a bit and then trying to pull it out. Hand pulling warm season grasses before laying down the cardboard and mulch can save maintenance later too.

  • Following the rhizome down as far as you can and pulling out as much as you can will help to ensure it will not have the energy to grow up into the sunlight again.