Mulch comes in many colors, people have long been using the ever present red mulch, and in fact I would venture it probably rivals plain mulch in volume. There are also golden mulches, that look like very fresh wood. Then there are more subdued brown mulches that look like slightly older wood.
The main advertised benefit of colored mulches is that they keep their color and so you don’t need to replace them as often. Personally, that doesn’t fly with me. I don’t lay down new mulch for coloring reasons, I do it to maintain a good thickness of 2-3 inches.
I do, however, use colored mulches sometimes in some places. I use them for their colors, as just another design element. You might plant a purple smokebush around some golden variegated hostas and it would look good with the foliage colors contrasting. You can achieve the same thing, and do more, by adding colored much into the area. So now you can contrast the plants against each other, and the mulch.
You can also contrast mulch with itself. My raised asparagus beds are covered in red mulch, and the ground level beds surrounding them are covered in gold mulch. It works.
This post though, this post is about black mulch, the post title I’m sure seems impossible. How could someone as dark as black brighten up a shady area? But what have I been discussing so far? Contrast. So, lets discuss contrast and shade.
Most flowering plants that do well in shady environments produce lackluster flowers, or atleast those that cannot compete with their sun loving cousins. In contrast (ahem), the foliage of plants that do well in shady areas tends to be spectacularly colorful with shades of golds and reds and blues, and of course greens.
However, foliage rarely rivals flowers for color, so make it pop, you need contrast. The most popular way to get contrast is to put clashing plants next to each other. A red-green plant looks crimson when planted next to a yellow-green plant (which itself ends up looking bright). Contrast helps to highlight the differences between the plants, making both look brighter and more vibrant.
So, since black is the ultimate contrast creator, adding black mulch to your shady areas might just brighten them up when paired with lighter colored plants.
Give it a try. I did, and as you can see in the picture (which by the way is Hosta ‘Great Expectations’ underneath my red laceleaf Japanese maple), I think it works.