What to do when a plant has new green growth at base? Snapdragon, salvia, lavender, granny's bonnet
I think this might be a rather basic question, but I really would love to know the answer (I'm a bit new to gardening).
A few plants are growing completely new stems up from the base, while the rest of the plant is still there. So it's like one main plant, with a baby plant growing up from the base at the same time.
I took a few photos to illustrate as it's quite hard to explain.
The first 2 pics are mini snapdragon (I think) with the first picture showing the whole plant, then the second picture showing the new plant at the base.
The next 2 pics are saliva.
The next 2 pics are lavender (though it doesn't show it as well, but there is fresh green coming in at the bottom).
The last pic is granny's bonnet, which I had already pruned once after flowering, then the leaves grew to that height and died and now I have a second lot of new green growth.
So a plant has new green growth at base, I was wondering if it's a sign to cut off the old growth?
And is it a good idea to cut off the old growth now, but not wait too long because of frost risk?
Or whether people leave plants like this, and then cut them at a particular month of the year?
Or what should I do ...?
Any advice is very much appreciated.