Have questions about mulch? What is it? Why should you use mulch and how do you apply it? Keep reading to answer these common questions and learn more about the benefits and considerations of using mulch in your garden.

Mulch is any material that is spread on the soil’s surface. This may seem oversimplified, but the general definition of mulch is very broad, and includes many materials that you might not immediately imagine.

Mulch looks great when spread around a garden and can tie a space together. Beyond aesthetics here are 8 practical reasons why you should lay down mulch on top of your soil this season.

  1. To prevent weed growth. Mulch blocks out light and smothers weed seeds.
  2. To conserve moisture. Most mulches are highly efficient at holding moisture longer than the soil below. Organic mulches tend to work best. A study done by the Weyerhaeuser Co. in 1969 showed a reduction in summer moisture loss of 21% and a reduction in the soil’s temperature of 10°F. All this accomplished by simply using a 2” layer of bark.
  3. To cool soil, and keep temperature consistent. Mulch regulates soil temperature, which can be especially important during the summer. Keeping your plants’ root systems cooler and uniform will lead to happier and healthier plants during summer extremes.
  4. To prevent erosion. A lot of work has been done in developing particular mulches that hold soil in place. Any mulch will work to some extent, but there are synthetic options that work exceptionally well, such as fabrics.
  5. To add organic material. Organic mulches will perform the other functions listed in addition to breaking down. As they break down and become incorporated into the existing soil these mulches add valuable nutrients and build soil health.
  6. To protect plants in winter. Mulch adds an extra layer of insulation to the critical root area in cold winter months.
  7. To keep fruits and vegetables clean. Mulch can prevent mud from splashing up onto vulnerable plants from the bare ground, keeping your produce cleaner and less prone to disease and rot.
  8. To preserve soil structure. Mulch protects your valuable soil by shielding it from the elements. Simple rainfall can pound bare clay soil into a brick-like texture, but a layer of mulch will absorb most of this abuse.

Carefully! Mulch, when placed correctly, can be a great addition to a garden. However, indiscriminately placed mulch may lead to severe problems for you and your plants. Here are a few points to keep in mind:

  • You only need 2-3” of mulch on any one area A thick layer of mulch can end up holding too much moisture in winter and become bone-dry during the summer. It can compact, keeping water and nutrients from passing through to the soil below. In some areas deep mulch can even be a haven for rodents. While fresh mulch may need to be applied from time to time depending on the material, be wary of letting it build up to an unhealthy depth.
  • Many plants don’t appreciate mulch piled against their trunks. A method of known as “volcano mulching” has been used for years, but don’t do it! The method involves piling mulch up against the trunks of plants, forming a tall mound, or “volcano”. When the mulch holds moisture that close to the bark, it leads to rotten wood and eventual plant death. Unless you are protecting a very tender plant for the winter, never place mulch against the trunk of a plant. Even when mulching for the winter remove the mulch from the base of the plant when the cold season is over. Many evergreen plants are especially susceptible to damage caused through this method.
  • Add nitrogen when laying down a dense organic mulch. Wood fiber mulches (sawdust and wood chips), and straw or hay, take more nitrogen to break down than they give back to the soil. When using these mulches, your soil can become depleted of nitrogen, robbing plants of an important nutrient. You can alleviate this by putting down 1 pound of nitrogen fertilizer per 1,000 square feet at the time of mulching.
  • Think down the road before putting down a persistent mulch. Things like rock and landscape fabric work well, but just try removing them later when you change your mind. If you plan to keep an area the same, and want to forget about it, these mulches might be a great option for you. However, if you like to change things around you may want to consider an organic mulch that is more easily removed.


  • Bark
  • Wood chips, Shavings, & Sawdust
  • Foliage/Leaves
  • Shells, Hulls, & Other By-Products
  • Compost
  • Straw & Hay

Many types of mulch exist. The type you use will depend on your preferences, situation, and location. Mulches fall into one of two categories: organic and inorganic. Organic mulches are any material found in nature that can be broken down by soil organisms. Inorganic mulches include man-made synthetics or materials like rock that can take a very long time to break down. Inorganic mulches will have a long lifespan but may look unnatural and will not give back to the soil like an organic material.


Bark: A classic choice in the pacific northwest, bark is an abundant resource and has become a staple for mulching. Bark is available in different grades, from fine to coarse and everything in between. Douglas fir is widely available in the area. Hemlock bark is another great option because it does not contain slivers. A more recent option is eucalyptus bark, which has natural weed suppressant characteristics and can be very attractive.

Wood chips, shavings, and sawdust: Used a lot in play areas, or areas that receive heavy foot traffic. These are not the best options for use in plantings, as they tend to pull a lot of nitrogen from the soil. Some wood products, like cedar chips and shavings, can even be toxic to plants! Great for pathways, utility areas, pet areas, and play areas.

Compost: Well-composted organic material can be a good yearly mulch, but must be reapplied often, as it breaks down into the soil quickly. Composted manures also work well around nutrient loving plants like roses.

Shells, hulls, other by-products: These are often specific to the area in which you live. Crushed nutshells, coffee grounds, rice hulls, and ground corn cobs are often used in areas that produce an abundance of such by-products. Hazelnut shells are becoming more popular in and around the Willamette Valley because they are in abundant supply and very versatile. Nutshells are usually much more durable and color-fast than other organic mulches. Mulching is a great way to recycle otherwise unused materials.

Foliage by-products: Leaves and grass clippings can work well in the correct situations. Leaves are great for winter mulches, although some leaves like oak can be toxic to some species of plants. Grass clippings are good to use at about a half inch at a time. Be sure to use grass clippings free from chemicals. Pine needles may work well in moderation around acid-loving plants.

Straw and hay: Good for winter protection and pathways. If you use this in summer, be sure to add extra nitrogen to the soil. Be aware that these can create a dense, impenetrable layer in neglected circumstances, and may sometimes carry weed seeds.


Rock: Not used as extensively here as in other parts of the country, rock makes an excellent long-lasting mulch. You can use lava rock, pea gravel, rock chips, and a multitude of other rock products.

Landscape fabrics: These are good for use on slopes and under areas of groundcover or other permanent plantings. The fabrics keep any weed seeds underneath from germinating, and help keep soil in place. Landscape fabric is a more permanent choice and is a pain to remove later if you change your mind.

Recycled materials: Recycled tires are one example of a mulch made out of old materials.

Farmington Gardens carries both bagged and bulk mulch. You can even order it online and have it delivered!