Answer: Peonies do best in a soil that is closer to neutral, so you may want to run some basic soil tests and see whether or not you need to add a bit of lime to raise the pH. You will find pH tends to change gradually over time, so it's a good idea to do this periodically so you can keep the pH within an acceptable range. The pine bark will break down slowly and have only a marginal effect on the soil pH. Pine straw or needles, on the other hand, would have a stronger acidifying effect.
Q&A Library Searching Tips