Fall is also a good time for thinning your Perennials, for sometimes thinning can turn into transplanting as well. I will use the Black-eyed-Susan’s as the example plant.
This popular sun loving plant not only increases by way of their crown root system, but also in the seeds they drop; causing them to be a plant that is hard to contain, though not impossible.
The tendency is to crop it back to the original purchase, the mother plant so to speak. But like anything old, (sorry to all you grandpas and grandmas), the reproductive ability is just a smidge off, if not gone altogether.
If you want vibrancy, and reproduction at its peak, you will need to whittle it back to the younger part of the mass. This will mean moving the location of the plant little to the left or right of where you thought it best originally.
After you decided what is to stay, and what’s to leave, you start removing them.
Here too you have choices; saving them to move them to another location would be to dig them up; or, pull them up if you have no other spot for them, and nobody you know would like them. Digging to “pitch” may need to be employed if they can’t be pulled up completely roots and all.
Thinning them back to a healthy crown size depends on how big you’d like it to be and how healthy the mass remaining is. Masses too old will “doughnut die”, meaning the middle )the oldest part of the mass, dies out, thus the term “doughnuting” .
To end this process, if moving the diggings, dig holes they’d be proud to live in and back fill them with enough groceries to help them thrive.