Understanding mulch terminology

By Melanie Mathieson
Gardening Guru

The last column provided you with some information on whether you may want to install mulch products in your yard or garden. The terminology around gardening can be a bit confusing at times, never mind a topic like that of mulch. This column will assist you in understanding the terms allied to the types of mulch you may consider for your garden.
Some gardeners are confused by the terms “mulch”, “spring mulch” and “winter mulch”. These terms are defined for you.
Mulch: In general terms, mulch refers to the product applied on top of garden soils to offer protection throughout all or some of the seasons. When mulch is referenced in this column and the sequential columns to follow, I am referring to mulch as an installation not necessarily disturbed or removed at the end of each season. Vegetable garden mulching is an exception to this since it is carried out on a seasonal basis in our region.
Spring Mulch: Spring mulch is applied to garden once the soil warms up in the spring. This is best if done after the last frost date to ensure adequate soil warmth for good plant growth. This method is used to suppress weeds and conserve moisture and can be applied to gardens that have plants that you replace on an annual basis like vegetables and annual flowers.
Winter Mulch: Doesn't actually keep plants warm, but maintains a more even soil temperature during the end of the winter season. Winter mulch provides plants extra protection when winter or early spring brings alternating periods of freezing and thawing and where there isn't enough snow cover to give plants a thick insulating blanket. Winter mulch is often recommended for protecting sensitive perennials and shrubs in our region. Winter mulch is often applied thickly at the base of a plant or shrub or right over the plant covering it entirely for the winter season. An example of this is covering rose bushes entirely with straw, leaves or peat moss each fall and then removing all of the mulch each spring.
Also confusing to gardeners are the terms “organic” and “inorganic” when applied to mulch products.
Organic Mulch: refers to a mulch product that is derived from plant material. Because this type of mulch is derived from plant material you will have decomposition of the product over time as well. Examples of organic mulches are sawdust, wood chips, bark, grass, straw, cocoa bean or coconut hulls, plant matter, etc.
Inorganic Mulch: this refers to a mulch product that is not derived from plant material. Be careful not to confuse the terms natural and unnatural with the terms organic and inorganic because gravel or stones occur naturally in nature but are not organic. Other types of inorganic mulch products include carpet remnants, plastics, rubber sheeting, etc.
Many gardeners have heard the terms geotextiles and landscape fabrics but are really unsure about what they are and how they fit into the garden.
Geotextiles: Geotextile is the name given to a family of geosynthetic fabric products that are synthetically manufactured for use in projects that involve soil surfaces or soil materials. These fabrics can be woven or non-woven and come in a large variety of weights and textures all specific to certain applications. A geotextile is used for reducing erosion, acting as a particle filter, separating types of soils from each other, providing a stable surface or barrier for a applying a product on the soil surface. Geotextiles are used in many engineered construction projects all over the world. This can include road building, urban development and bridge building just to name a few. In our region the use of geotextile is commonly used in the construction of logging roads. Geotextiles such as landscape fabric are derivatives from the industrial products used in the landscaping and gardening industry. When using in the garden, geotextiles should be non-toxic vegetation, inert to common chemicals and be mildew and rot resistant. Those products with UV protection and stabilization are also best for landscape use. The rubber sheeting used for pond lining is also considered a geotextile and should be graded as fish-safe if you are going to use it in a pond with fish and plants.
Landscape Fabric: Landscape fabric is a form of a geotextile that is manufactured specifically for the landscape and gardening industry. The different types of fabrics available, are woven, non-woven or spun-bonded synthetic petroleum products. These products are usually dark grey or black in colour and come in many different “weights” and thicknesses. When laid out on the ground or soil surface around plantings, these products provide a physical barrier against weeds and tree roots. Using a barrier for weed prevention is not new, of course. But prior to the development of geotextiles, the standard barrier for weed prevention was plastic which prevents roots from getting essential water, oxygen and nutrients. It can also keep roots too wet, leading to an increase in root-rot diseases. Unlike plastic, landscape fabrics breathe, letting air and water through, and don't adversely affect the health of plants. In fact, research has shown that trees and shrubs with landscape fabrics around them grow just as well as ones without fabric, yet without the same weed competition. Before purchasing a landscape fabric for your project make sure to read the label to make sure this is the right product for your application. There are usually recommendations on the packaging helping you to apply the right product for the right job. Landscape fabric is an investment so choose the right product to ensure you get the best value for your money.
I hope that this column has eliminated any confusion you may have had about some of the terminology that is commonly used when describing landscape and garden projects. By clearly understanding these terms you can look forward to the next columns in this series that will provide you with some more in-depth information on mulch and the installation of a mulch product.