I have many (maybe 15) philippine violet plants in my yard. We had a mild winter but the plants have turned black. They are about 5 feet tall. Should I trim them back to the ground, half way, or leave them alone?
I would leave them alone until you're sure you won't have any more cold weather, the black leaves are probably dead and should be removed in the spring, but for now they can act as protection to the rest of the plant if you get another frost. I don't grow these so I don't know what the right thing is to do to them in the spring, hopefully someone else will have some advice for you, but I would definitely leave them alone now.