Dig It!: MULCH
by Sage and Snow Garden Club
October 1, 2007
Mulch can be any material that covers the ground and keeps the ground moist, suppresses weeds, reduces temperature fluctuations and, additionally, organic mulches will improve the soil as they decompose. Loose mulches let air and water through. Weeds that already have roots can usually push through loose mulch. Organic loose mulches improve the soil as they rot and are a magnet for the soils' best friend, earthworms. Barrier mulches suppress growth of all weeds, including seedlings, but do prevent organic mulches put over them from adding organic matter to the soil. Barrier mulches need to be covered with loose mulch to keep them from degrading in the sun or blowing away.
Winterizing mulches are thick mulches applied to newly planted areas or to plants that may be susceptible to winter kill Winter mulches include straw, leaves, and pine branches, which are applied 6 to 12 inches thick after the ground freezes (or is close to freezing). They are left in place until spring. Be sure to draw mulch away from plants in spring so the sun's warmth can penetrate the soil.
Applying mulches - Fine, dense mulches should be spread in 1-inch thick layers. Medium density mulches, like shredded bark, should be spread 2 to 3 inches thick. Very airy mulches, like salt marsh hay, need to be spread at lest 6 inches (and up to 12 inches) deep to be successful insulators. Do not pile mulch (except winter mulches) next to plants. Be careful not to apply mulch too heavily or directly next to tree and shrub trunks since this may cause rotting of the trunk. You can also double mulch by laying down a sheet of perforated plastic first, then adding fabric mulch or even old newspaper (with predominantly black ink) or pieces of cardboard and then placing your organic mulch on top.
Instead of carting your cardboard to the dump, recycle it at home by using it as mulch. It makes great weed barriers and still allows moisture to get to the soil. Put down a layer of cardboard and pile organic mulch (grass clippings, leaves, or compost) on top. You can also pile manure over the cardboard for a fertility boost. Next spring, poke holes through the crumbled layers and you are ready for your planting (some people call this lasagna gardening). .
Lawn clippings build soil structure, moderate soil temperature, and conserve moisture. Allow the clippings to dry before applying. Apply a 1 to 4 inch layer that does not form a dense mat. If you use lawn clippings in flower beds, be sure that there are no grass seeds in the mix.
Chopped leaves suppress weeds, build soil structure, and reduce soil temperature. Be sure to tear, chop or compost leaves before using them as mulch as whole leaves will mat and not allow moisture to penetrate. Use leaves as mulch in winter or spring with a 3-inch layer. In our area, most leaves will break down into alkaline compost, so you should use sparingly around plants that prefer more acid soil conditions.
Pine needles build soil structure, suppress weeds, and increase soil acidity (good for acid-loving plants). Apply a 2 to 4 inch layer around shrubs, and trees.
Bark nuggets conserve moisture and suppress weeds. Apply a 2 to 3 inch layer around shrubs and trees, preferably over a roll-out mulch.
Straw or hay builds soil structure, suppresses weeds, moderates soil temperature, and conserves moisture. Apply a 6-inch layer at planting time and as needed through the growing season. Straw usually contains fewer weed seeds than hay.
Paper and newspaper suppress weeds and conserves moisture. Use them in pathways between beds or rows. Cover with a thin layer of more attractive mulch and turn under when partially decomposed.
If your need for mulch is to insulate, this snow is the best material. In those spots in your garden where the snow pack is high in winter, you may not need any additional winter mulch.
Plastic weed barriers are reusable, suppress weeds and conserve moisture. Use them beneath straw or grass clippings in places that are renovated at the end of the season.
Black plastic sheeting warms the soil and suppresses weeds. The light reflective patterns that accompany red plastic mulch benefits tomatoes and some other crops and deter nematodes. Lay down plastic and anchor with rocks or soil. Plastic can also be used to warm soil so you can plant earlier. Use heavyweight reusable products.
Landscape fabric suppresses weeds. Lay this down at planting time and cut slits for plants. It may be difficult to cut and may not allow plants to spread beyond the cut holes.
Good luck with winterizing your garden. The Sage and Snow Garden Club meets at noon on the second Tuesday of each month in the Pinedale Library. Contact the Garden Club at firstname.lastname@example.org or Box 2280, Pinedale, WY 82941 or bring your gardening questions to our meeting.