In recent years, the use of dyed wood mulch has become more and more popular with homeowners. It's often used to create eye-catching walkways, colorful backdrops for ornamental plants, or to add visual interest to otherwise barren parts of the landscape.
Unfortunately, dyed wood mulch is not without its problems, and many gardeners wonder whether or not it's safe to use on their plants. The answer is yes, and no.
Today, some manufactures of colored wood mulch still use dyes made from petrochemicals. This means that as the mulch breaks down, these chemicals leach into your soil (and local waterways) where they can be absorbed by the roots of your plants.
The good news is that things are improving. Many of the larger manufactures are switching to dyes that are vegetable-based and biodegradable. Still, make sure you read the package before buying. Even if a manufacturer claims that the mulch is organic, it doesn't mean that the dye is also safe.
Chromate copper arsenate (CCA) is a chemical wood preservative containing chromium, copper and arsenic (a carcinogen). Although phased out by the EPA in 2003, pallets and other scrap wood containing CCA may still find their way into mulch. Mulch containing CCA should never be used around plants intended for consumption. Again, read the labels carefully. Look for colored wood mulch made from raw lumber, or mulch featuring the MSC Certification Logo, which certifies that the mulch is free of CCA-treated wood.
To keep prices lower, some manufacturers may use powdered dyes to color the wood. This quickly sloughs off and either becomes airborne (where you may inhale it) or it attaches to the bottom of your shoes and you take it for a walk around the garden.