Compost and Mulch

A mulch is something that physically covers the soil but is not incorporated into the soil. Mulches are often used to decorate the yard but are used for erosion control, to save water and to suppress weeds. Traditionally mulches are thought of as being things such as chunk or shredded bark, but other materials are considered mulches. These include crushed stone, recycled materials such as rubber. To be effective, mulches should be applied 2-3 inches deep. An option with most mulches is placing fabric or plastic sheeting underneath the mulch as an added protection against weeds. This is only beneficial when the soil underneath will not be planted in on a regular basis. Punching multiple holes in the fabric creates spaces for weeds to germinate.

When planting annuals and perennial in flower beds containing mulch, consider using a pre-emergent herbicide such as Preen, Barricade or Dimension as added protection against weeds instead of fabric or plastic sheeting. Apply the pre-emergent after all annuals and perennials are planted and the mulch is in place. Keep in mind that weed seed can accumulate and germinate in the mulch itself over time. Pre-emergence products will help control these.

Organic Mulches (chunk or shredded bark): These are inexpensive and offer a natural look for the the landscape, but they decompose color fades in the sun over time. They should be refreshed with an additional inch of mulch per year to alleviate this. However, the decomposition adds valuable organic matter to the soil. Dyed or stained shredded wood mulches are available that are colorfast for much longer periods of time than natural products. Various bark or wood mulches can be purchased bagged or in bulk from local garden centers and landscape product centers. Local green waste facilities also offer mulch relatively inexpensively but their mulches may not look as quite as "finished" as products from garden centers and landscape product businesses.

Rock Mulches: Rock mulches are becoming more popular. They are available bagged and in bulk. They offer a wide spectrum of colors and are much more permanent in the landscape. Two to three inches must be applied to be effective. Some limitations of rock mulches includes that they are much heavier than organic mulches - making them more difficult to handle - and often times more expensive up front.

Recycled Mulches: Many products made from recycled rubber are becoming popular. They offer a more natural look comparable to bark but are more permanent like rock. They are often used in play areas and on pathways. Darker colored versions may heat up more than bark products in the summer sun. They are also the most expensive mulch option of those listed.

Compost: Composts consist of partially decomposed plant and/or animal matter. Composts are incorporated into the soil through tilling or other methods. They improve the soil by improving drainage and nutrient holding capacity as they further breakdown. To improve soil, incorporate 2-3 inches into the soil annually. To maintain the soil in its current condition incorporate an inch annually. Plant based composts are generally potentially less salty but contain less nitrogen. Conversely, animal based composts are potentially more salty but often have a greater nitrogen value. Ideally, compost should be applied in the fall so that it has a chance to break down to improve the soil. Applying in the fall additionally allows any excess salt to leach through the soil. A lighter application can then be made in the spring, if needed. Spring and summer application of compost are usually just fine, though. Adding additional nitrogen fertilizer to the soil when they are tilled in speeds breakdown and alleviates possible nitrogen deficiencies caused by soil microbes as they decompose the compost. Additionally, do not plant in straight compost, it is not a replacement for actual soil. For more information about compost, access the USU Extension fact sheet, Preparing and Improving Garden Soil here.