During the Winter, most plants hunker down and save all their energy for when the weather warms up. New leaves are a rarity. My Sage follows this pattern.
This is Purple Sage. Currently more grey than purple, but I'm sure the colour will return in the Spring.
This one is the Variegated Sage - yellow and green.
Both of these Sages have lost most of the leaves on their lower stems. Only a cluster of leaves at the end of each branch remains.
I am going to try to propagate the plants by taking some cuttings and I will also to try to re-invigorate the parent plants by a process I call "mounding". This is what these processes involve:
Firstly, clean up the bare crown of the plant, removing from the pot any fallen leaves and other debris
Cut a few suitable stems for potting-up. They should be about 15cm / 6" long
Fill the bare centre of the pot with fresh new compost, mounding it up so that it stands well above the level of the pot rim.
That's it for now! Hopefully, the plants will produce new shoots from underneath the new compost. At very least, the bare stems will send out some roots. When this happens (some months later probably), you will be able to snip them off and plant them straight away.
Trim the cuttings to a suitable length (I use a craft knife). Cut the stems on a slant, preferably just below a leaf joint. Remove any dead leaves and all but a few of the healthy ones. Having too many leaves will cause the cuttings to lose an excessive amount of moisture through transpiration. (Looking at my photo again, I think maybe I should have removed a few more of the leaves. It's not too late...)
Dip the stems in Hormone Rooting Powder, and push them into a pot of moist compost.
Place the potted cuttings somewhere light and frost-free, and keep the compost moist but not wet. Most of them (but probably not all of them) will take root, and within a couple of months you will have a number of new Sage plants. You will be able to tell when / if the cuttings have rooted, because they will start to produce new leaves.
Some people would cover the pots with plastic bags secured in place by rubber bands, to create a sort of miniature greenhouse, but I usually don't do this because I think it produces too much humidity, which can increase the chances of fungal growths taking a hold.