It is what everyone wants, right? Ok, let me rephrase. It is what every gardener wants, right? I think the most difficult concept for new gardeners to grasp is cutting back your perennials produces more flowers.
Yes, visiting your homes in the last two weeks I have repeated the phrase “Cut it back!” more often than any other. To which I hear, “I was afraid my plant (perennial) would die.”
What you don’t understand can be scary. I am here to calm your fears. First, let’s define the word ‘die’. I find it strange, but very true, that this word needs defining, but let’s. A dead perennial would be a plant without any live roots, stems or leaves.
If you were to cut your perennial back, even all the stems and leaves of your plant – guess what? The roots are still alive! So cutting back your perennial does not kill your entire plant, it puts it in a dormant state until the roots push out new stems and leaves. Now, if you pour Round-up on your perennial, the leaves, stems and roots would die, giving you a dead plant.
Second, an herbaceous perennial by definition is a plant with soft, green stems that die back to the ground and grows again. Cool, so even if the top growth is cut, slightly dries out or is killed by winter, the roots are alive to give your plant the opportunity to REGROW!
I hope you are starting to feel a little bit better about cutting back your perennials. If you are still unsure ask ANY greenhouse or garden center (not a box store) what they do with their tired perennials in July and August. I will not keep it a secret. We cut them back – most to within 2” of the soil and fertilize them with root stimulator (high phosphorus). When we do that the plants are AMAZING and beautiful by September 1ST, EXACTLY when you are ready to plant! This works in your home gardens, just as well as for us.
Now for the details, here are some of the most common perennials that we sell at Colorscapes that benefit from cutting back.
Astilbe: Prone to dry out come July and August. You will know they are drying out, if the leaves are crispy. If you plan to water them or if nature begins to give us more rain, cut them back 2” from the ground. You will soon see a flush of new bright green leaves. A sporadic bloom may pop up in September when the weather is cool too!
Blanket Flower (Gaillardia): Some varieties are floppy. If yours flops over to the point where it looks bad, cut it back to 3-4”, fertilize with root stimulator and then water only when very dry. Blanker flower will rebloom in 2-3 weeks.
Coneflower (Echinacea): Here at ColorScapes the wind plays havoc on our plants. As you can see by the picture below. Yes, even though it had many flowers, I cut it back HARD. I will update the progress as it flourishes again, but by mid to late September it will be beautiful – a bit shorter and sturdier, but full of flowers.
Coreopsis Threadleaf: I have a love/hate relationship with Coreopsis. As it seems to either look fabulous or terrible. (Ha! Sort of like the ups and downs of my life). When it is full of black seed heads I first cut 2-3” off the top of the plant. Many times at that point it will revive itself, but sometimes a hard haircut is needed! Here is a picture of some at ColorScapes after a hard haircut and then 1 week later! Blooms!
Dianthus: Many new varieties of Dianthus will bloom more than once a season, but remember their best bloom is ALWAYS in April and May. As soon as that first bloom is over, grab your hedge sheers (my favorite gardening tool, of course) and set the blades just above the foliage and cut. If your dianthus leaves are raggedy or brown (usually a sign of over-water) you may cut into the leaves as well. Keep doing this all summer, probably 3 or 4 times throughout the summer to promote MORE FLOWERS!
Nepeta: I do like this plant! It blooms so well and needs so little care. As soon as your plant flops open and looks like a circular flopped over mop that is a sign to cut it back. Often when it flops you will already see a nice new tuft of leaves in the center. Keep those new leaves and cut the old foliage. At my place I easily cut Nepeta back four times a summer. Keep those sheers nearby!
Salvia: A great perennial that MUST be sheered for rebloom. This is plant that I cut back the most in established landscapes. I sheer back Marcus after it blooms down to the basal foliage (the group of leaves very close to the ground). Caradonna and other taller varieties, on the first sheering I cut back by about half, then after that I will sheer these to the basal foliage as well. No basal foliage? Don’t worry, cut to about 3” regardless and you will soon see basal foliage and flower buds forming.
It is important to remember not to over water when your plant is cut back. After cutting back, water when it is dry, but then wait till you see leaves before you water it. Remember how a plant uses water…it transpires off the LEAVES on hot days. Now if the plant has no leaves, it uses very little water. When new leaves begin to form, the water needs will then go up. I tell you this only because here at Colorscapes our cut back plants sometimes get watered daily (too much) by a “Happy Waterer”. If this occurs the roots which were alive will rot! Then you WILL have a dead plant!
You can do this! Got questions? Stop in ask us…we want to see your tired garden revived and GORGEOUS this FALL!