Do the acids from pine mulch damage plants?

No. Organic acids in SPM® actually benefit the soil by lowering pH and providing organic matter. Hardwood mulches can contain phenolic acids which can be harmful to some plants and there is confusion at times between good acids and potentially damaging acids. Most plants are acutally grown in pine bark media at commercial growing operations, therefore pine acids are not an issue.

Gro-Bark® Canada Red SPM® is a beautiful mulch product that will help you maintain your landscapes in a safe and
natural way. Canada Red SPM® is now over 25 years old and it is still the number one choice of landscape professionals in Ontario. It is very consistent and always arrives at a job in a form that is easily spreadable. Unlike stringy fibrous mulches, once Canada Red SPM® is established at a 4” depth in a bed, it is easy to top up with just an inch or two in subsequent years because it flows so easily. Great aroma and colour makes Canada Red SPM® a great aesthetic choice as well. 

Canada Red SPM® increases moisture retention and root zone cooling, which minimizes
frequent irrigation. The added benefits of adding organic matter to the soil together with the acidifying
properties of pine mulch make a perfect ground cover for gardens, planters and tree plantings.
Gro-Bark® Canada Red SPM® has proven weed suppression characteristics unlike any other. Compared to untreated
bare soil, Canada Red SPM® has the best weed control in areas where chemical control cannot be used. Compared
with other mulch types, weed suppression is 80% higher with Canada Red SPM®.*

* Based on a 2010 trial