We get it. Black mulch, like a black leather jacket, looks really cool. But in our experience, plants – especially young plants – don’t do well surrounded by black mulch. When Archer Services installs plants in your landscape, we want them to thrive. For this reason, we avoid mulches with dyes and use organic mulch, instead. Here are the reasons why.
Black Mulch is Hot! Hot! Hot!
An extreme climate like the one we have in Southeast Texas requires a mulch that will mitigate, not intensify, the heat. Your summer wardrobe likely comes in lighter, brighter colors than the clothes you wear in winter. Dark colors absorb heat at a much higher rate, and on a 100-degree day in Houston you will be miserable if you are outdoors dressed in heavy black clothes during the heat of the day. Sadly, the plants in your landscape don’t have the option of stepping inside an air-conditioned building when the temperatures rise.
Black mulch attracts and retains more heat from the sun. It raises the temperature of the soil it covers considerably when compared to other mulches. This additional heat stresses plant roots, impacting their ability to absorb water and nutrients. If the plants are still young and tender, this will be enough to kill their roots before they have a chance to establish themselves in your garden.
In addition, the rate of heat absorption of black mulch means the soil will dry out faster, which is the opposite of what you want mulch to accomplish. Undyed mulch is always the best option in a hot climate.
What lies Beneath: What You Can’t See Can Hurt Your Landscape
Many dyed mulches are made of recycled wood waste. Basically, they’re made of trash. This waste wood can come from sources like old hardwood pallets, demolished buildings, and discarded decking. In some cases, it contains pressure-treated CCA (Chromium, Copper, and Arsenic) lumber. These waste-wood products are ground up and sprayed with a tint, often carbon based, to cover up their inconsistencies and give the product a uniform color. Once the dyed mulch starts to break down, the chemicals used to preserve and color the wood can leach into your soil.
A good mulch should break down to enrich the soil so that it not only protects your plant roots, but it also nourishes them. Dyed mulch, on the other hand, leaches the dye along with other possible contaminants (such as chromium, copper, arsenic, lead, and formaldehyde) into the soil. The chemicals in the wood can harm or kill beneficial soil bacteria, earthworms, and in many cases the plants themselves.
I really like how black mulch looks! When can I use it?
If you like how black mulch looks and insist on using it, the right black mulch can be an option, but only in the right circumstances. First and foremost, you should use the a black much that is certified to not contain dangerous treated woods. Look for products that say they are made of untreated wood or shredded bark, rather than waste wood. If the source of the wood is not listed on the bag, assume the worst. Look for brands that say they use safe dyes or label their products as eco-friendly. In the US, the Mulch and Soil Council will put an approval label on any mulch products that don’t contain dangerous treated woods. It may cost more than the dyed mulch, but it’s worth it.
If you do use a safe, non-toxic black much, the heat will still be a problem for many plants. For this reason, only use black mulch around well-established plants with deep roots that are less likely to be killed by the additional heat that the dyed mulch will retain. Never use it around newly installed plants.
If black mulch is a bad idea, what should I use instead?
The best mulch is one made with organic materials (such as shredded wood and bark) with no chemicals or dyes added to it. This type of much will break down over time and release nutrients into the soil, helping your plants grow and thrive. It will help retain water by hindering evaporation, and regulate the temperature in your garden. In our next blog post, we will discuss what to look for in a good mulch and go deeper into the benefits of using one.
