Is Colored Mulch Toxic – Safety Of Dyed Mulch In The Garden

Molinia caerulea 'Variegata' on the flower bed, sprinkler with red dyed mulch. Ornamental plants for landscaping.
Image by SvetlanaKlaise

By Darcy Larum, Landscape Designer

Although the landscape company with which I work for carries many different types of rock and mulches to fill landscape beds, I always suggest using natural mulches. While rock needs to be topped off and replaced less frequently, it does not benefit the soil or plants. In fact, rock tends to heat up and dry out the soil. Dyed mulches can be very aesthetically pleasing and make landscape plants and beds stand out, but not all dyed mulches are safe or healthy for plants. Continue reading to learn more about colored mulch vs. regular mulch.

Is Colored Mulch Toxic?

I sometimes encounter customers who ask, “Is colored mulch toxic?” Most colored mulches are dyed with harmless dyes, like iron oxide-based dyes for red or carbon-based dyes for black and dark brown. Some cheap dyes, however, can be dyed with harmful or toxic chemicals.


Generally, if the price of dyed mulch seems too good to be true, it probably is not good at all and you should spend the extra money for better quality and safer mulch. This is pretty rare, though, and usually it is not the dye itself that is of concern with the safety of mulches, but rather the wood.

While most natural mulches, like double or triple shredded mulch, cedar mulch or pine bark, are made directly from trees, many colored mulches are made from recycled wood – like old pallets, decks, crates, etc. These recycled bits of treated wood can contain chromates copper arsenate (CCA).

Using CCA to treat wood was banned in 2003, but many times this wood is still taken from demolitions or other sources and recycled into dyed mulches. CCA treated wood can kill beneficial soil bacteria, beneficial insects, earthworms and young plants. It can also be harmful to people spreading this mulch and animals who dig in it.

Safety of Dyed Mulch in the Garden

Besides the potential dangers of colored mulch and pets, people or young plants, dyed mulches are not beneficial for the soil. They will help retain soil moisture and help protect plants during winter, but they do not enrich the soil or add beneficial bacteria and nitrogen, like natural mulches do.

Dyed mulches break down much slower than natural mulches. When wood breaks down, it requires nitrogen to do so. Colored mulch in gardens can actually rob the plants of the nitrogen they need to survive.

Better alternatives to dyed mulches are pine needles, natural double or triple processed mulch, cedar mulch or pine bark. Because these mulches are not dyed, they will also not fade as quickly as dyed mulches and will not need to be topped up as often.

If you want to use dyed mulches, simply research where the mulch has come from and fertilize plants with nitrogen rich fertilizer.

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