Even the neatest, longest-blooming, most dependable repeat bloomers in the perennial world can use attention now and then to look their best. The perennials we've listed as "Easiest Best" are in this category.
You may ignore these plants' shortcomings in order to enjoy the least possible maintenance. Alternatively, you can deadhead during the bloom season -- clip off spent flowers as they develop, to keep new blooms coming -- and cut back when bloom finishes.
As you decide which course to take, do not imagine that you must work with bent back and floral scissors to deadhead and cut back. Such cuts can be made with mowers and weed whips (string trimmers).
Benefit from deadhead/cut back: Big betony (Stachys micrantha)
Need time to grow: Coral bells (Heuchera hybrid 'Caramel')
May have distracting brown spent flowers: Hardy Hibiscus
Big betony (Stachys micrantha) is one of the best of the best perennials, good for
the front row because its bloom season is long, it is very willing to rebloom if deadheaded, and it is not terribly unsightly during its down time even if untended.
Here's a no-gloss look at its appearance through the year, and the difference it can make if the plant has some minimal attention.
Note: The cutting back can be done with scissors, one spent stem at a time. It can also be done with shears or a mower, a rougher cut that removes both old leaves and new, thus leaving a temporary gap -- the plants will regenerate.
Now take a look at big betony at the very end of the growing season. The photo below was taken in late October, after frosts have occurred that ended annual plants' year but before the killing frost that will stop perennial growth.
There are ten big betony plants here. Most have dry seed stalks showing above the foliage, and still bear the somewhat tattered leaves that are part of those stems. These plants bloomed, were enjoyed for that color, but left "au naturel." What you see there are big betony plants grown at the lowest possible care level.
One plant (arrow) was cut back after its first bloom. Its place was relatively bare for about two weeks after the cut, but since then it has had all new foliage. This is a best, easiest perennial with just a bit of extra attention.
Despite the varied treatment, all of the plants in this group will be back in equal health and bloom next year.
As a related aside: The lush light green mounds in the background are bigroot perennial geranium (G. macrorrhizum), another "best, easiest" perennial. It's one of that group which does not need even the minimal extra attention just described for big betony to remain looking so fresh. However, there is always a trade-off: Its bloom season is not so long as big betony's.
The best perennials are long lived and not aggressive. You can expect them to be contributing members of your landscape for a long time, without becoming pests through overgrowth.
However, these plants can't be rushed. Plant them with enough space to grow healthy, and wait.
If we want to crowd them, we have to remove some plants by the end of the first summer so the rest can grow healthy into maturity.
Two points: First, that even a long-blooming perennial has a peak bloom time when it is most likely to look like its catalogue photo. Second: Intervention can improve even the most gloriously blooming plant.
We use Hibiscus as an example because the bigger the flower, the bigger the spent bloom. Hardy Hibiscus has huge blooms. Each lasts one day and then separates from the stem.... but it may lodge among the leaves and become unsightly.
Deadheading these plants can keep the color show pure, and may extend the bloom period. That happens because younger and lower stems may be encouraged to keep growing if no seed begins to form on the first flower stalks. Those younger stems can produce another flush of flower buds.
Note: Hardy Hibiscus does not change its following year performance if deadheaded. It will be healthy and free blooming in future years regardless of your choice in treatment.
Below, the bigger picture.
Now, for the overall look of Hibiscus in bloom, comparing peak bloom to end bloom, and giving you a look at pristine flowers sharing the stage with some hanger-on brown petals.