Should All Plants In The Herbaceous Border Be Cut Back Now?

Generally gardeners advocate that most of them should be to stop dead growth falling into the soil around the plants and rotting on the soil.
However, you should leave hostas well alone as well as bergonias, violas, primulas and obviously any plants which will flower around Christmas time or January.
Try to make sure that when you do your cutting back the ground is damp but there is no frost.  Frost will mean that the soil is very hard and the plants will be stressed.  Chop down the plants until they are about 4 inches or 10 cms above the ground.
However, if you live in a very cold part of the country then it is sometimes davisable to leave on the top growth, since this can give the plants a little more shelter than they would usually have.  But otherwise, cruel as it may seem, the plants need to be cut back.