What do I use to treat powdery mildew on hemlock shrubs?
The following articles should be of some help to you: https://www.gardeningknowhow.com/problems/get-the-cure-for-powdery-mildew.htm
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm
Two summers ago, we planted a row of hemlock to serve as a privacy hedge. They are planted about 4 feet apart and some are beginning to touch branches. Over last winter the snow depth exceeded the height of the tree and broke a few branches. Should I prune anything to make them stronger and grow together more quickly, or just leave them alone? If pruning is in order, should we prune now before the Pennsylvania winter months and while the tree is dormant, or wait until spring?
This article should help you:
https://www.gardeningknowhow.com/ornamental/trees/hemlock/pruning-hemlock-trees.htm
Can I prune huge Hemlocks in August? I really need to. Growth this year is unprecedented.
You can prune lightly in August. Try to do the minimum needed can as early in August as possible. Finish with the complete pruning in early spring, which is a more acceptable time for pruning.
I have Canadian hemlocks growing as a privacy screen in the front yard of our rental home. Our tenant thought it would be a good idea to prune them and cut all of the branches off of the bottom of the trees. The tree trunks are now bare about from the ground up about two feet. I am very concerned they will die. Will the top branches eventually move down the trunk like a pine tree? Do you have any suggestions on making them back into a privacy screen? Or are the ruined and the bottom branches will never fill back in? Any assistance would be greatly appreciated.
This article should help you with pruning: https://www.gardeningknowhow.com/ornamental/trees/hemlock/pruning-hemlock-trees.htm
The trimmer wants to chip the droppings and use as mulch under the bushes. Is this ok?
Using hemlock mulch around ornamental plants and trees is a healthy and attractive soil amendment. For more information on hemlock mulch, please visit the following link:
https://www.gardeningknowhow.com/garden-how-to/mulch/using-hemlock-mulch-on-veggies.htm
I did not realize this hemlock plant could be poisonous and I pulled/cut them down to the base but could not dig out the root as the ground was too hard. I immediately took a shower. Is there anything else I should do?
Washing it from you skin is the right treatment.
Please contact either Poison Control or a physician if you see any skin irritation.
https://www.gardeningknowhow.com/plant-problems/weeds/poison-hemlock-control.htm
I removed a branch almost back to the point where it joins the main trunk, thinking it was dead because one of its whorls didn't have any needles on it. But was later told it probably was just shedding its needles and the cut should have been made just above the needle whorls. I'm upset as I've created an unsightly gap in the tree. Will the branch continue to grow out where I cut it so the gap is no longer there?
You will likely have to wait and see.
Here is a link on pruning.
https://www.gardeningknowhow.com/ornamental/trees/hemlock/pruning-hemlock-trees.htm