You can cut back the Phlox and Cushion spurge now if you like but wait until early spring for the Hakonechloa and Clematis. Wait until the Clematis is showing new growth and cut back to the second set of strong buds from the bottom.

Is your Phlox P. paniculata?

Both the euphorbia and the hakone grass develop lovely fall color and neither needs to be cut back, so I'd just leave them be (the euphorbia is fully evergreen here, as well). After a few frosts, the grass will brown and dry but you can just rake the old fronds away. And I wait to hard prune all clematis until late winter although you can do so earlier.

Otherwise, you can generally cut back and clean up most other perennials at any time you prefer, although a great many gardeners will leave them in place until spring.

It's said that there may be some benefit of not cutting back till spring with regards to hardiness. The danger I might fear is if they're not committed to dormancy yet, and you cut back...they try to grow and get a nasty freeze on new growth.

Agree dbarron. That is why I said to wait on the Hakonechloe which would be iffy in zone 4. All the others would be fine in this particular case.

I do not cut back my Lavender until spring either. Anything planted in fall I leave untouched for the first year too. If I were zone pushing I would definitely leave the foliage. I am generally a fan of fall clean up though.

Thank you all. I will wait for the Hakone Chloe grass like you say but because it is my first year with this and it is iffy in my zone should I completely cover with 2-3 inches of mulch. Would that help.

yes my phlox is paniculata.