What is the pH of your water?

@mad_gallica (z5 Eastern NY) Our water is pretty close to neutral, about 6.7. However water does not buffer pH well and would not change soil pH strongly.

It will be a few days until I have time to buy some of that lime, read the label and tell you what I think.

@klem1 Here is the product label if that helps.

So many issues with this post, it is hard to know where to start!!

First, soil pH skewing one way or the other a point or two is not going to significantly affect rate of growth. Could have other implications but not reduced or zero growth. More likely to be cultural issues like root congestion, lack of required nutrients or inadequate watering.

Second, directions for lime use to increase soil pH is given for square footage, not volume. Based on Al's 5-1-1 mix recipes, pH is neutralized with approx. 4 Tbsp lime per 5 gallons of mix. Since you don't want to neutralize but only increase slightly, I'd suggest you start with less and test. (would be way easier to use a acid planting mix for this purpose. It's what I use for all my containerized ericaceous plants).

Finally, water can and does work very well to alter soil pH. Gardeners in more arid climates with a hard or alkaline water supply typically will acidify their irrigation water with vinegar or sulfuric acid.