The world of the garden is divided into two groups which do not overlap. The first group is made up of those who avoid at all costs cutting anything from a tree, shrub, perennial or annual. You can tell these people because every time they consider picking up a pair of pruning shears, you can hear grinding of teeth, twisting of hands, and apprehensive moans.
And then there’s group two – what I call the slash-and-burn gardeners. I tend to belong to the latter group and one of my professional and personal goals throughout my life is to move as many members from group one to group two.
There are many reasons to prune plants, from maintaining health (both physical health for the plant and mental health for the gardener!) To structural stability and even artistic expression. But one of the great overlooked summer garden practices is trimming annuals and perennials.
The big summer discount is a absolute essential in the garden. It can make your garden more beautiful, your plants healthier, save you maintenance time, and generally make you a happier gardener. Here is a list of some reasons to cut back on your summer annuals and perennials:
Beat the flop
Some annuals and perennials may be just too big for their botanical breeches. We have all seen it. You plant coleus or lantana and it hits the ground running. Then, in the middle of summer, the big banana peel dance begins. The whole plant divides in the middle, leaving a large space in the middle of the plant. It’s a pretty unsightly mess and can kill a well-planned summer border. Cutting them down to half or a third at this time of year can allow plants to branch out more and maintain a more stable structure during the rest of the summer.
Tame the beast
Sometimes an annual or perennial can be a little too proud of itself. This can be a big problem (literally!) With trees. But with herbaceous plants, it’s often easy to give them a little mid-season boost to keep them from getting taller than you want them to be. Giving your fall lantana, coleus, or aster a summer haircut isn’t an admission of a failed garden design. You can actually plant herbaceous plants with the intention of keeping them a little smaller than they want. But if you do that, you have to remember to actually do the reduction …
Generate repeated flowering
Some herbaceous perennials give us a pretty show of color at the start of the growing season, then turn to green spots for the rest of the summer. But if you time your reduction well, some of these plants can give repeated flowering performance later in the summer.
The key to reduction for repeated flowering is to make the cut as the flowers wilt, but before they put too much energy into seed production. Done well, the energy that would have been spent forming seeds is devoted to regrowth of shoots and eventually flowers.
It does not work with all types of herbaceous perennials. Plants like daylilies that produce separate leaf and flower growth do not respond well to repeated flower pruning. Others that produce both flowers and leaves on the same stem – catnip (Nepeta species) for example – works fine.
Of course, you can also go in the opposite direction. With some annuals that we grow mainly for the impact of the foliage (coleus), in fact, you don’t want flowers. Once the plants start flowering and then sowing, they dramatically reduce the growth of new foliage and this can put a major drag on the show. For these plants, simply pinch the flowers as they form and hold the foliage all summer.
Controlling leaf diseases
We all love our herbaceous peonies. Their spring blooms illuminate our days. The cut stems add grace and elegance to our dining tables. They can take us back to grandma’s garden. But frankly, in July some of them can get downright ugly. When powdery mildew turns the leaves from a cool spring green to a dusty gray, they stop adding anything positive to the garden.
Once herbaceous plants are badly affected by something like powdery mildew, the first thing you need to understand is that these leaves don’t do much photosynthesis. They don’t help the plant much. When I see this happening in my garden, whether it’s a peony or something else in my perennial plantings, the slash-and-burn gardener in me takes over.
I cut the foliage down to the ground. If the plant grows back in the second half of summer, all the better. If not, at least I don’t have to watch this mess for two or three months.
And honestly, if you’re a plant and can’t stand the heat, get out of the garden!
In our nursery at Yew Dell Botanical Gardens, our nursery manager Jacob Stidham hates spraying insecticides. But he also enjoys growing a long list of milkweed species for the local monarch population. The problem is, if you grow milkweed, milkweed of any flavor, you’re bound to have aphids … lots and lots of aphids.
But rather than resorting to atomizing the aphids with a nasty insecticide, Jacob simply cuts down the milkweed plants. Most of them grow like bean stalks, so they recover quickly. And once the plants are out of the nursery – once they are happily growing in your garden – they tend to attract fewer aphids.
Finally, there is the potential to save water by reducing your annuals and perennials. Here’s the scenario: Your garden looks great. But now it’s July and you’re off to Michigan for three weeks. The neighbor’s kid you paid in the past to water your garden has turned out to be a little shy to be completely reliable.
Well here’s a tip. Go out and mash all your annuals to a third or a half size before you hit the road. Plants will use less water. If the neighbor’s child misses a watering or two, the plants are more likely to survive.
And in all likelihood, by the time you return, the plants will have returned to their pre-cut size.
Enjoy the lake!
Paul Cappiello is the Executive Director of Yew Dell Botanical Gardens, 6220 Old Lagrange Road, yewdellgardens.org.