How much acidity does Tsuga Canadensis (Canadian Hemlock) require usually?

Question

have some hemlocks that are slightly yellowing on the needles and just was wondering if this might mean that they dont have enough acid in the soil.

checked the acidity with a self powered meter that you stick in the ground with a copper and metal ends and it says that acidity is around 6 or 5.

so maybe I need more pine park chips or what other methods would help?

or could it be something else?

thanks for your answers!

Answer 1

It could  be the normal shed it goes thru in the fall. needles turn yellow but not all on the same branch. Hemlock are also prone to wooly adelgid. (aphids) check for those by looking for cottony like masses.    Your pH sounds fine.  Aluminum sulfate is used to lower the pH. you can get that at most garden centers.