pruning back perennials

Asked this on the perennial page and no one answered so perhaps I'll have better luck here. I have out of control Alonsoa, Hot Lips Salvia and a blue daisy bush (name not known) that need pruning back, but need to know how far back I can go without killing the whole plant. All are very woody and taking over parts of the garden.

I have the Alonsoa and several Salvias and if I don't stay on top of them and they get out of control then I've cut them back pretty hard and they've come back fine (no blooms for a little while though!) I've never cut them back all the way to the base but I've cut them back pretty far. For the blue daisy I'd have to know what it is...blue daisy makes me think Felicia but they are usually nice neat compact little plants, I can't picture them being really woody so I wonder if yours is something different?

I have May Night salvia. I deadhead it several times a season to keep it blooming. The trick is to snip off the spent flowers just at the base because the new buds are forming below. It takes extra time to be careful, but the 4-5 months of blooms are worth it.
I do the same thing with campanula (bellflowers). I discovered the new buds coming on a canterbury bell plant and realized that I had been just lopping off the other campanulas, buds and all. Once you really look at the stems, you can see the new buds.
The other woody plant you have might be caryopteris, aka blue mist shrub. It blooms late in the summer and has clusters of daisy-like blue/purple flowers. It won't re-bloom, but snip off the deadheads to show off the good flowers better.

Here is the picture of the blue/purple daisy plant I was inquiring about. The second picture is of the whole plant. I was wondering how far back I can prune.Thanks

And here is the whole plant.

It does look like Felicia. I've never had one long enough to need to prune it so I can't give you any really good advice on how far you can prune it back without hurting it. With plants that I'm not sure how to prune, I'll look back along the stems and see how far down there are still green leaves, usually you can cut back anywhere within that "green zone" and they'll be fine. Some plants you can cut back into the brown area where there aren't any green leaves, but some things won't come back from that, so unless it's a plant that I know can handle that I'll stick with pruning in the green zone.

Most perennials need cutting back or lifted and divided after about 4 or 5 years to keep them in good shape and vigorous growth going, but if you cant lift and divide the clumps, then give them a good prune when the flowering season has past OR early spring when you see the new soft shoots/buds start to break, the best way to do it is to have a good sharp knife or cutting tool and look down each stem for a new soft bud/leaf starting to form, cut just above this so the new dud gets light and this will soon fill out the space of the old top part you cut away, do this all over the plant, you should give a good handful of granular feed or your preferred plant food at this time to help the plant get growing good and strong again, it will soon reward you with nice new fresh growth that will flower better and have stronger flowers too. as Ecrane has already said, there are some plants (woody stems) that wont grow from the old wood where there are no green growth, things like Lavenders etc dont grow from the old wood and they should only be pruned to the green softer stems or the plant will just die off without making any fresh greenery, so these should be pruned AFTER flowering just enough to remove that years flowering stalks, you can do this with the shears like cutting a hedge, go over the top with the cutters about 2 inches of the top comes off, other green hard wood plants can be pruned to new buds on the stem in spring early summer as the new leaf buds grow, but with these, you may miss out on flowers for that year as they need time to form new flower buds as some flower on the previous years growth, but it can save the plant from growing too large or bare at the bottom where it looses it's appeal and gets just top growth, maybe if your not used to doing this, you can just cut half the plant back one year and the next half the second year and that helps to keep the sap rising over the years without shocking the plants/shrubs. hope this helps you a little, good luck. WeeNel.