Keep it Cool with Mulch Alternatives
Dark colored mulches used in garden beds and landscaping in both commercial and residential areas are aesthetically appealing. But there is a downside to using this material in your landscaping.
Darker mulches absorb the sun’s heat more than lighter material. In fact, mulch can become extremely hot during sunny summer days, which makes the soil hotter, sometimes becoming hotter than pavement - this is bad news for your plantings and other living things in the soil.
High temperature surfaces also increase the temperature of stormwater flowing into nearby streams. Long Creek experiences significant spikes in temperature immediately following a summer rain shower. Temperatures exceeding approximately 24° C (75.2° F) have been shown to be detrimental for brook trout habitat, and streams exceeding temperature thresholds may not be able to support certain species of aquatic organisms that would be expected to reside there.
Natural, undyed mulches maintain a more consistent temperature and are less likely to overheat the soil and damage plants, insects, and other living things.
Dark colored mulch overheating can also cause excessive water evaporation if not applied at the right thickness. A thin layer for aesthetics requires more watering, while 2-3" of mulch will help reduce evaporation. Old bark mulch should be gently removed before applying new mulch to help keep the soil surface porous and reduce mounding around plants, which causes more rain to shed off the surface rather than soak into the soil, depriving the trees, shrubs and other plants the moisture they need to thrive.
Creeping phlox, creeping thyme, and bearberry also make good ground covers in sunny conditions.
Additionally, bark mulch fires are becoming a growing concern during the summer months when hot, dry windy conditions make bark mulch very susceptible to ignition by careless disposal of smoking materials.
Instead of using dark mulch:
Switch to a native / non-invasive groundcover (e.g. creeping phlox, creeping thyme and bearberry)
Use undyed and natural mulch
