You know the kind to which I’m referring. So many of our clients call it (not so affectionately) gas station mulch or red mulch. We don’t put down dyed mulch for our clients’ properties, but I know there are homeowners who are fond of dyed mulch so I thought I’d try to shed some light on this question. Some people feel it makes the plants stand out more and like the color contrast of foliage and flowers against the mulch. But, the question at hand is really is it safe?
Logically we tend to question the safety of the dye itself. In reality, the problem usually does not lie with the dye. Most dye (not all) used to color mulch is vegetable based dye which is safe. However, some dye used can have petrochemicals in it and while the levels are deemed safe to use on soil I wouldn’t recommend using that kind of dyed mulch in vegetable gardens. Ask before you purchase dyed mulch what the manufacturer uses for dye.
The real question with dyed mulch is the source of the wood. Most dyed mulch comes from recycled wood. Well, to this effect, most of might say say, “Oh great, it’s recycled”. Not always. What type of recycled wood is being used? Some recycled or salvaged wood contains a substance called Chromated Copper Arsenate, more commonly known as CCA. This wood contains chrome, arsenic and copper. Prior to 2002, pressure treated wood contained CCA. When a wood is treated with CCA, arsenic can leach into the soil raising your soil’s arsenic level.
So how do you know that your red mulch isn’t coming from a source of older pressure treated wood? Look for the Mulch and Soil Council (MSC) Certification Logo. This logo ensures that the wood in the dyed mulch you’re purchasing does not come from wood containing CCA. If you’re buying your dyed mulch from a bulk supplier, that is, not commercially manufactured and bagged, ask the supplier where the wood is coming from, the type of wood being used and the type of dye being used. Or, of course, just use natural, undyed mulch. I for one think it’s much prettier in the garden!