In the landscape most gardeners and homeowners wait until early spring to trim back any old dead leaves and stems from last years perennials. Here at the nursery we have all the plants under plastic in their hoop houses for the winter. This prevents the wind and weather from naturally blowing away some of this old plant material.
Starting in late fall and going through the early winter season it is important to do a dormant trim back of almost all of the perennial material. This removes all that dead organic matter and prevents disease like powdery mildew from spreading inside a hoop house. This trim back looks different depending on the type of plant however. Most perennials will die back all the way to the ground so for these we just remove almost everything from the pot and wait for new growth in spring. For woody perennials such as Russian sage we just trim these back slightly and allow the remaining buds to break in spring. No reason to cut back 100% of that nice growth the plant added in summer/fall the previous season and that will give you a larger plant faster in spring for sale.
Dianthus like the ones pictured above are technically semi evergreen, meaning they remain green under the plastic all winter and even slowly put on tiny bits of growth. Small ones like in the picture aren’t trimmed at all but larger leftover ones just get trimmed around the edge of the pot to prevent them getting to large and floppy come spring. This is just another example of work we do through the off season that not only keep us busy, but really can make a difference in the quality of the perennial material come spring.