I have some sage plants that winter over nicely.
There are plenty of leaves on them from last year. Should I use these along with the new growth later on?
Or should I remove them or prune the plants back to hard wood?
When I lived in Michigan we never had to prune our sage plant, only when we harvested leaves for seasoning which were taken off the ends. I would not harvest the leaves at the bottom, but not because they might not be as useful but I keep seeing sage bushes that only have leaves at the top when this transpires. Now I am not sure if the bush would replace them over time or not but I enjoy a nice full bush rather that one that only has leaves at the end of the branches.
No pruning. Use living rather than dead leaves for your uses. I usually wait until after the sage has bloomed and starting pushing leaves in earnest before starting to harvest sage for the season. Usually for me in NY State that is mid-summer. Before that point, I only nick a leaf or two here and there.