Using stone mulch in your garden

Phew,
It sure was a hot one today. The crew was out at a clients house working hard to remove stone "mulch" that had been installed by the previous homeowner. This can be quite an undertaking, especially when the installer didn't use a suitable landscape fabric to keep the stones from "pumping" into the soil. A sturdy landscape fabric will keep the gravel from working its way down into the soil during the annual freeze-thaw cycles and block most weeds. Black plastic is not recommended because it does not allow air or water to pass through it to the soil.
Let me be clear, stone has a place in the landscape, and can even look great as a change of texture and color, however, I urge caution when considering rock as mulch. The rock will heat up in the sun and reflect heat back at your plants, creating a micro-climate. The extra heat can cause your shrubs stress, both in summer and bright winter days. Boxwoods and Azaleas in particular are sensitive to this. Another reason is that stone has no nutritive value and thus does nothing to enrich the soil. If weeds do get into your stone, it is much more difficult to remove.
I always prefer non-dyed hardwood mulch, as it conserves moisture, keeps down weeds, keeps the soil cool and makes your yard more attractive, among other benefits. Dyed mulches can contain chemicals that can chase away your beneficial microbes. Mulch simplifies mowing and it keeps string trimmers and lawn mowers away from unprotected tree trunks. Mulch can be the visual “glue” that knits a landscape together. A natural mulch such as shredded bark will feed the soil as it breaks down slowly over time.
It’s important to remember that mulch is not permanent. You can’t just freshen the color up every spring. All of the organic mulches decompose wherever they touch the soil. Weed seed will sprout in this layer. The region of decomposed material eventually becomes slimy or hard and it can repel rainfall completely. All mulched areas should be renewed every couple of years by raking out the old material, re-spreading it thinly in place and then covering it with fresh mulch.

Mark Griffith is a Virginia Certified Horticulturist and a lead designer with Nautilus Garden Designs in Hampton Roads www.nautilusgardendesigns.com