If you have plants that look floppy and open like this Salvia in the picture below,
instead of like this one, nice and full and upright–
then you might want to consider cutting it back almost to the ground. Just leave the lowest leaves at the base and cut off all the faded, bloomed-out stems. I know you hate to lose the color, but the flowers are almost done anyway. If you do it now it will rebloom in another four to six weeks and perk up your August garden.
Other perennials that will benefit from this type of treatment are Nepeta (catmint), Centranthus ruber (Red Valerian) Geranium ‘Brookside’ (cranesbill) and Aquilegia (columbine). You only need to leave the lowest leaves, new leaves will soon grow and fill in to make the plants look nice again.
Are there perennials that you don’t want to deadhead or prune in summer? For me the answer is yes–if I want a plant to reseed, I don’t want to remove the old flowers. I allow most of my penstemons to go to seed because I like it when they self sow. Here’s Penstemon ‘Rondo’ a few weeks ago in full bloom. I love this penstemon! It’s so hardy and drought tolerant and the color range is fantastic. And, it self sows, adding new colors every year. We planted a couple of Rondos in this corner of the garden, and now there are five or six, each a slightly, or even wildly, different color. It’s almost completely done blooming now, as you can see in the next picture. I’ll leave a few of the stems alone, for seed, and cut the others down to the basal foliage. If you deadhead it, this penstemon reblooms in late summer–one more reason to like it!
Penstemon glaber, a native in Southern Colorado, also reseeds here, so I let some of the old stems stay and cut the rest back. I know there are people who don’t bother to cut back the old flowers, and other people who can’t stand the sight of a seed stalk in the garden–it’s really a matter of personal preference, and there isn’t a big right or wrong to it.
Some perennials bloom so much in the summer that they sort of bloom themselves to death. One that comes to mind is Gaillardia (blanket flower). Here it is in my garden.
Butterflies like it, as you can see. It will bloom like this until October! That much energy put into flowering doesn’t leave much energy to grow foliage and the plant can be exhausted by fall. To ensure that it comes back next year, cut it back hard in mid to late August. That will give it a chance to grow lots of healthy new leaves and get stronger before winter. It needs a good number of leaves at the base of the plant to be able to winter over and bloom well for you next year.
Just a reminder: Perennial Favorites is closed in July, but we will reopen in August.