i have a question about cutting back annuals as well as perennials. seems that around june or so, some plants get floppy and “leggy”. for instance, the containers with petunias and zinnias are growing like mad. i know to deadhead, but they are getting a bit floppy and i was wondering if i cut them back if they’d recover and continue to bloom. same for some of my perennails (especially salvia and veronica) are there some that benefit from a mid-season trim and some that should be left undisturbed?
Marcy, I have that same question. Have not had time to research it yet. I have some violas that are very floppy now and I’m considering giving them a “shave”. I hope that someone can give us some guidance on this question.
The best resource I’ve found on cutting back perennials for bloom and reform is Tracy D’Sabato Aust’s “The Well-Tended Perennial Garden.” She has lots of good tips and charts for helping you get on a schedule.
Some general rules for pinching and cutting back perennials: With plants like Salvias and Veronica that first bloom in the spring and tend to get more and more floppy as the summer progresses, an alternative to deadheading is to simply cut them back to a few inches above the ground (shave them), after the first flush of flowers. They will grow back with more compact growth and a new flush of flowers that will almost rival their initial bloom. A plus is it is a lot less time-consuming than deadheading. The down side to this method is if the plant is in a prominent spot in the bed you will be looking at the stubble until it grows back. Fall blooming perennials can be pinched back until mid July to make compact growth and summer blooming perennials can be pinched back in May, but it will probably delay flowering (which can be used to extend the bloom time if you cut back some, but not all of a particular plant.) Here is a good article on the Illinois extension website that goes into more details about pinching perennials.
In terms of the annuals, most will also respond well to a shave, as long as it is not too late in the season for them to recover. For instance, violas prefer cooler weather so if it is getting too hot for them even a shave won’t revive them. Petunias prefer hot weather, so don’t shave too close to the cold weather.