Wow, my Marshall's Delight never gets that tall. I pinch most of my monardas when they are about 10 inches tall and always get bloom. Not sure about the others you mentioned. Mary

I've never heard of pinching back Achillea. What's wrong with taller plants? I have perennials in the 12 ft range.

Aunt lou, if your library has it, check out "The Well Tended Perennial garden" by Tracy DiSabato. It goes into great details about how to pinch and prune back plants for control and better, fuller looks. Several on here recommended it to me, and I check it out from the library. Would love to have my own a reference tho. From what I understand, you can prune back all perennials except things like daylillies. Just make sure you do this BEFORE your plant starts to set buds. It states you may have some delays in blooming, but the plant will develop more branches and blooms. Someone on GW showed a pic of False Sunflower. The flowers were beautiful, but I commented I didnt care for plants 5 feet tall. She said they can be pruned back and kept more compact. I am going to try that on several of my perennials.My achillea, gets too floppy. I highly recommend that book tho,cause one cant rely on my memory,lol.
Tammy

Ditto to the Well-Tended Perennial Garden. That's the first thing I thought of when reading this post, too. I got it for Christmas this year, and it is an invaluable source for pruning info. The author prunes back lots of things, especially late-blooming perennials that tend to get tall. She talks about pruning in layers to shape the plant and extend the blooms over a longer period of time, as well as pruning for height at a certain point, which seems to result in shorter plants that bloom a bit later. Very cool reference book!

Or Google "Chelsea chop" -- it's a popular method used in UK gardens to effectively shorten some of the taller mid- to late-flowering perennials by cutting them back to half in early summer (June-ish). When they do flower, they will be significantly shorter than normal.

Coolplantsguy, thanks for that Google search. I have already cut back my sedums but was wondering whether I could do my salvias, too. Apparently I can.

Tammyinwv, I put the Well-Tended Garden on my library hold list. Thanks for the recommendation :-)

I just pruned back my Autumn Joy Sedum hoping they'll stay a little shorter this year. I plan to slightly prune my balloon flower as it gets very tall and not so sturdy. I also recommend The Well-Tended Garden.

I cut back only half of the plant, that way you have flowers twice instead of only once. Not mums tho, they get whacked with hedge trimmers 3 times.

I whacked my balloon flower back to 8" the last week of May and WOW! What a different plant!! It produced five times as many flowers and stayed nice and compact the rest of the season. From now on it gets the same treatment. Also cut back perennial geranium/cranesbill and it bloomed right up to the end of October.
Don't tell my sedums but they're in for a haircut!

Definitely trim back the monarda! I tried it after reading the Well-Tended Garden. I topped it all, but cut it shorter around the edges. The shorter part supposedly blooms later. Didn't for me, it all bloomed at the same time but it really gives a better effect. I have already cut back my balloon flowers, some of them were already 3'tall. I'm wondering if I should cut them back again next month.

Wow! Thanks for all of the great advice! That book sounds great and I see that amazon has it available free shipping. As soon as this rain lets up I'm going out tomorrow and whack the monarda! It is so hard to stake it up every year and sometimes plants in front get smothered out. Last year that happened in front of my honorine jobert anemones_--- they got so tall and thick and heavy [gorgeous though in their pristine white!] that they fell forward and smothered out some ice star daisies. Anyways, thanks so much!

aunt lou