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Sheet Mulching

Reclaiming Weedy Wastelands


Tuesday, September 18, 2012

Mulch — it happens naturally in undisturbed habitats. All the dead parts of a plant fall to the ground and create a carpet of organic material that fungi, bacteria, and other creatures such as arthropods can feed on and in turn feed the soil and plants growing in it. In gardens, it can happen, but mostly it doesn’t. Gardens are, after all, constructed environments, and plants are introduced from far and wide to please the needs and whims of the gardener. Those same gardeners usually have an idea of how things should look that don’t always include letting all of the dead parts of a particular plant remain where they fall. Flower petals and leaves, little twigs and even bigger branches are fastidiously removed to maintain the tidy look most folks like best.

Returning some of the lost organic material to the scene can be done aesthetically by applications of mulch that has been engineered for uniformity. Layering compost, wood chips, or any organic material on the soil surface will discourage weeds, reduce water loss, increase the organic matter component of the soil, and provide soil microorganisms with a source of food. Mulch layers need to be replenished as they break down.

One very effective method of mulching that is particularly suited to reclaiming turf or weedy wastelands for more sustainable plantings is sheet mulching. The grass or weeds are cut down to the ground, and then layers of biodegradable materials are applied on top. The first layer should be something that can be overlapped to prevent any sprouting weed seeds from working their way upward. Cardboard, newspaper, even natural fiber cloth or old carpeting will do. The thickness is not as important as overlapping the pieces by six to eight inches to form the weed barrier. On top of this, compost or other organic mulch material can be layered to a depth of several inches. Once the mulch is in place, holes can be punched through to plant the new garden. Monitor the soil moisture beneath carefully, so that the mulch layer does not create an anaerobic situation below. If you’d like to learn more about this technique and lend a helping hand to beautify a downtown park, read on.

On Saturday, September 22, the Ocean Friendly Gardens (OFG) program (sponsored by the Surfrider Foundation) will hold a hands-on workshop at Spencer Adams Park. This “Lawn Gone Without Herbicides” will, by applying the OFG principles and practices, continue their work of transforming the site into yet another Ocean Friendly Garden. The main chores will be to shape the site for ease of rainwater capture and rebuild the soil health through sheet mulching. This is the second phase of remaking this park. The city has already relocated a downspout to divert rainwater into what is called a “sponge garden.” These areas allow water to percolate back into the soil slowly instead of running off-site.

The workshop will be held 10 a.m.-2 p.m. Snacks are provided, but be sure to wear appropriate clothes and bring a water bottle. The park is located at 1216 De la Vina Street, next to the Louise Lowry Davis Center. For details, visit oceanfriendlygardens.org.

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Virginia Hayes, curator of Ganna Walska Lotusland, will answer your gardening questions. Address them to Gardens, The Independent, 122 W. Figueroa St., S.B., CA 93101. Send email to vahayes@lotusland.org.