I've never whacked these plants, but if you have a lot of them you could whack one and see how it does. Let them be little guinea pigs for you. This gives me an idea. You could keep a little notebook and document when you prune something and put little notes telling you if something worked or not. Like "Pruned phlox on June 10th. Note: It did not bloom." I bet since you live so far north that some of yours will not have as long to grow and bloom again though. I might have to try this myself.

*We* don't tend to cut things back. However, we have unofficial, assistant whackers, often known as deer, that have their own ideas of what should be pruned back when. Since both phlox and balloonflowers are among their favorites, we have seen how they react.

The balloonflowers have been cut down to about 6 inches in early June, I think. The result was a much sturdier plant that bloomed at pretty much the same time. However it was before they started setting buds. Phlox didn't set more buds once the first ones were eaten. Done earlier in the season, they are fine, but do still end up the same height.

Personally, I wouldn't cut back/whack fall bloomers now (ornamental grasses including Chasmanthium, sedum, etc.) it's late in the season. Even if they bloom, the foliage forms won't be at peak as should be mid-summer (specifically referring to ornamental grasses and Chasmanthium). Why would you want to cut them down, anyway? A major attraction of ornamental grasses in the form - the flowers are secondary to most people, and if you whack them now, they aren't going to re-gain their lovely form until late in the season. Grasses aren't going to become fuller by haircutting like some other perennials will, so you really have nothing to gain and everything to lose by whacking those back now (again - including the Chasmanthium). Best time to cut down ornamental grasses is spring before or when new growth begins.

Sedum - well, you could, but again personally I wouldn't. I like how the greeen heads look this time of year, plus I don't want to delay the flowering. Might be a good idea if they're floppy, but if that's the case then re-examine positioning of them or consider dividing, they shouldn't flop (soil too rich or too much shade will cause flopping, and may flop if need to be divided).

Being a caterer, I can't help but respond that:
As to the early/late timing of the 'whacking', I guess you need to convince the deer that these plants should be the appetizers, not the entree.

I know this isn't funny for you, but i also know you have a good sense of humor!
I do thank you for the helpful experiences.
best,
Mindy

as usual, your response is very wise and helpful.

i have had trouble w some sedum flopping, so i will re-examine their conditions. i thought the proverbial latest timing for their whacking was july 4th, but maybe i mixed them up w/ asters.

i have alot of problems w/ chasman. latifol. drooping. i'll never forget seeing it at Wave Hill where it was shorter and VERY straightup. mine always have to be staked/tied, even in full sun. so i did whack them by 1/2 when they were 15"H in may, so we shall see.

as to 'why i would want to whack now', the answer is because i didn't get around to it when i should have, earlier in the season, and the plants in question are too lanky or tall for their spot. and i don't care when they bloom or plume as long as it happens. this is an arboretum garden really so the flowers play off the mostly foliage
and it doesn't really matter when they bloom. the gardens are also really packed cheek to jowl and that means some often unhappy conifers, so i try to keep the surrounding perennials cut back when necessary to let in light to those wonderful evergreens.
best,
mindy

I tend to miss getting things clipped back when I should sometimes, too. We farm, so I'm usually in the fields when I should be doing my pinching and clipping. I have cut back both sedum and balloon flowers pretty late. The sedum look ridiculous for a week or two, then bush back out and look fine. They do have smaller bloom heads, but stay upright. The blooms on the balloon flowers were a bit later, but didn't seem to be any smaller.
I am very seriously thinking about chopping back some phlox that have powdery mildew. Even if they don't bloom this year, at least they wouldn't be tall AND hideous :)

does late mean as late as now? thank you
mindy

Yes, I'm ashamed to say I've done it as late as now. I don't make a practice of it..the sedum really do look goofy for a little while, but they come out just fine in the end.

Quote: "...and the plants in question are too lanky or tall for their spot."

You supplied yourself with the answer to your problem. If plants are too tall/lanky for their spot, either they're the right plant in the wrong place, or the wrong plant in the right place. Either way, they don't belong in said place - move them to conditions where they will perform as they should.

now just because i complimented you, don't go getting cocky on me.

I believe you have overlooked the possibility, the fact, in fact, that the platycodon in question are behaving just as they should in their position, but that i would like to tweak that habit. I do that all the time w/ certain plants: an oakleaf cimicifuga that i whack back early so it doesn't get to its normal height- which would block too much sun from a special conifer behind it.

or rudbeckia herbstsonne that i whack by half at least once every season- to keep its height from dominating its neighbors. etc etc.

for many places in my gardens, there are a number of plants that could work in a given spot. But for some spots, there is just ONE variety that satisfies me, so i tweak it to make it work in that spot.
best,
mindy

Ah...I see...yes, I did overlook that possibility....

Still, isn't that too much headache? Why don't you just plant something else that is the right whatever then you don't have to be bothered with it - ?

Eh, but if it makes you happy, tweak away :)