Answer: While hemlocks (Tsuga) do prefer an acid soil, they also need a humusy, evenly moist yet well drained soil. Over watering or under watering could cause them to drop their needles. Over fertilizing could also shock them and possibly "burn" their roots. In a windy location, newly planted evergreens would benefit from protection from wind as well, to try to minimize transplant shock. Based on your description, I am not able to diagnose precisely what has stressed your trees. I would suggest you contact the supplier and/or your county extension right away to try to determine more specifically what has caused the problem and what to do next. I'm really sorry about your trees.
Q&A Library Searching Tips