Should Gardeners Amend Clay Soil?

Q: The online retailer where I bought my butterfly bush recommends
gardeners not amend clay soil. Agree or disagree? 

A: It is true that in most cases no amendments are needed when planting a tree
or shrub. Amendments create a paradise for roots, which they are reluctant to
leave when they need to explore the surrounding soil for new sources of water
and nutrients. An exception could be made if you are planting a big shrub bed
and can amend the entire area. And keep in mind that amendments are useful
when you’re planting annual or perennial flowers. I know this flies in the face
of recommendations I have made over my career but I am not too old to
change my mind.