Is Coloured Mulch Safe for Your Garden?

The use of coloured mulch has increased over the last number of years, as the bold and rich colour offers an attractive look for landscaping while continuing to offer the benefits of mulching. Unlike natural, non-dyed mulch, which tends to fade to gray, coloured mulch can hold its colour for a year or longer.

However, with these benefits, public concern has also been raised regarding the use of coloured mulch. The primary question is:  Is Coloured Mulch Safe for Your Garden?

What about the dye?

The typical dyes used for colouring mulch are iron oxide-based and carbon-based. Iron oxide, used to produce red mulch, is commonly known as rust, and is used extensively in paints, cosmetics, and even used to dye flowers.  Carbon, used to produce black mulch, is an element often used for ink or paint. Both bases for these dyes are considered natural, non-toxic and safe for handling. Most other colours are made with vegetable-based colourants, also from naturally occurring elements.

A study (“Are Mulch Colorants Safe”) conducted by the Mulch and Soil Council, determined that colourants typically used for coloured mulch are deemed non-toxic and when used properly, would not have any negative effects on the environment.

Of course, a savvy customer should ask about the product they are purchasing, and the company should know about their product. For example, at Denbow, we know that our mulch is coloured with non-hazardous, safe for the environment, ingredients.

What is in the wood?

As the colourant used in coloured mulch has been generally deemed safe for use, eyes have turned to the content of the wood. The use of recycled wood is a beneficial practice for the environment, yet depending on the content of the wood, harmful toxins (such as lead) could be lingering from past uses.

When purchasing coloured mulch, then, it is important to consider the wood content. In an effort to improve the quality of our products, Denbow produces a number of our own materials, including processing our own mulches. We work with select sources of material to minimize foreign material in our finished products. Our red and black coloured mulches are made of locally recycled wood, free from these contaminants.   

Will it affect the soil?

There is a concern that when using wood mulch, the carbon of the wood will interact with the nitrogen in the soil, using the nitrogen to help the decomposition process, but in turn, pulling the nutrients from the soil. Coloured mulch actually decomposes at a slower rate than regular wood mulch, which means the nitrogen is removed from the soil at a slower rate.

Use of a nitrogen-rich fertilizer is encouraged, as for whether or not mulch is used, the soil can benefit from the implementation of a regular fertilization program. It is recommended when adding new mulch, to take the time to remove old mulch or be sure to cultivate your existing mulch on a monthly basis in order to help healthy decomposition.

At the end of the day, if you are looking for a pop of colour to refresh a garden bed, or seeking to landscape a new area and considering an alternative to the natural mulch, coloured mulch is a safe and beautiful option. Is coloured mulch safe for your garden? Yes, Denbow’s coloured mulch definitely is.