You have probably seen that colored mulch in people's yards (the red and black types really jump out at you) and wondered if dyed mulch is safe to use. If you have an organic bent, then your natural reaction (without knowing the specifics behind the product) is that you have no desire to handle something colored by chemicals (and no desire to have potentially harmful materials leaching into the soil). So let's explore the issue to learn if this is truly a bad product (and, if so, what specifically is bad about it).
Dyed Mulch Can Be Safe to Use, Depending on Source of Wood
Specifically, many homeowners ask if dyed mulch (also called "colored mulch") is safe to handle when mulching plants or safe to use around food crops. But the dye on colored mulch is less of an issue than the type of wood on which the dye is applied.
Dyes used in making colored mulch have three different origins, and all three are harmless:
- Red mulch is dyed with iron oxide. This is a compound of iron and oxygen. We are all familiar with the result of this compound oxidizing: We call it "rust," which is red. "Rust" may not have very posititve connotations, but it is quite safe to have around the garden.
- Black mulch is dyed with carbon. This should not surprise us, since we associate carbon with charcoal.
- Other dyes for mulch are vegetable-based and therefore organic.
Unfortunately, the question of whether dyed mulches are safe does not end with determining the composition of the dye.
The source of most dyed mulch is recycled wood. So far, so good. But the problem is that some of that recycled wood may be treated with the preservative, creosote (which is harmful). In other cases, the source of your mulch is old wood pallets, and we have no idea what purpose they may have served in the past. If they were used in the transportation of chemicals, they may be contaminated.
One of the worst sources for mulch is CCA-treated wood, which, used as a mulch, can raise the arsenic level in your soil (CCA stands for chromated copper arsenate). Although the use of arsenic in making pressure-treated lumber was largely banned after 2002, it is hard for gardeners to say with certainty that a part of the source of the dyed mulch that we are buying is not old, leftover CCA-treated wood.
Enter the MSC Certification Logo, which certifies that a mulch or soil product is free of CCA-treated wood. MSC stands for Mulch and Soil Council. According to MSC's Product Certification program, "Certified mulches and soils can be found at major retailers and garden centers across the country." So look for the MSC Certification Logo if you wish to improve the chances that the dyed mulch that you are buying is safe for humans to handle.
Precautions to Take When Using Dyed Mulch (for You and Your Pets)
If the colored mulch that you are using is not certified, there is no reason to take a chance in handling it with your bare hands. It is recommended policy, therefore, to wear garden gloves whenever you will be touching this product. But what about our dogs and cats? Since we regard our pets as part of the family, guarding their health as we would guard our children's health (and since they do not normally wear protective gloves) it makes sense to keep them away from areas covered with such mulch.
Erecting a fence is one option for implementing this precautionary measure. One of the least expensive types of garden fencing that you can erect to keep pets out is a chicken-wire fence. This kind of fence is also very easy to set up, since all that it involves is pounding stakes into the ground and attaching the chicken wire to the stakes. To prevent dogs and other animals from tunneling under it, however, it helps to dig a trench and partially bury the chicken wire in it. A good feature about taking this extra measure is that your fence will now double as a barrier to keep garden pests out, such as groundhogs and rabbits.
So much for the issue of dyed mulch, human health, and how safe it is for your pets. Whether or not colored mulch affects plant growth is a separate question.