Fall cutbacks are often considered part of garden cleanup. The flowers have finished blooming, the leaves are starting to yellow, and the stems are drying out.
But cutting back perennials also changes the design of a garden.
Some perennials, when you cut them back, go from being two or three feet tall, occupying the middle of a border, to being a groundcover. And that changes not only the appearance of the plant itself, but also the plants around it.
Daisies
Daisies (Leucanthemum) are probably the most obvious example.
Daisies tend to flower all at once, and then finish flowering all at once. There’s very little reblooming happening in most of the gardens I work in.
Once they’re done blooming, I usually cut them back to the first or second large leaf below the flowers. This removes the spent flower heads, but still leaves a mass of green foliage.
Later, once the leaves start looking scraggly or yellowing, usually around late September or early October here in the Niagara region, I cut the stems all the way to the ground.
This leaves a little rosette of new leaves at the base.
And now the plant has completely changed its function.
When the daisies were blooming, they were a focal point, or at least an attention attractor. After the first cutback, they were still a mass of foliage, creating some structure and perhaps framing the plants behind them.
But after the second cutback, they’re a groundcover.
And that groundcover now highlights the plants behind it.
For example, if you have turtleheads (Chelone) planted just behind the daisies, the turtleheads will be much more visible once the daisies have been cut back to the ground.
The turtleheads haven’t moved. They’re still growing in exactly the same spot. But their position in the design has changed because the plants in front of them have changed.
Black-Eyed Susans
Something similar happens a little later in the season with black-eyed Susans (Rudbeckia), which tend to continue blooming later than daisies.
Black-eyed Susans also lend themselves to a layered approach to cutbacks, perhaps even more so than daisies.
If you’re somebody who enjoys spending a lot of time in the garden, or simply has the time, you can remove the individual flowers as they finish blooming.
Each stem will often produce several blooms, sometimes three, four, or five, with secondary and tertiary flowers opening after the first ones. So you can cut off the spent flowers as you go, keeping a fresh blooming appearance for longer.
Eventually, once the flowers are all finished, you can cut the stems back to the ground.
Like daisies, black-eyed Susans leave a layer of foliage at the base. It’s a little taller, coarser, and less glossy than the daisy foliage, and usually quite dark green. But it still functions as a groundcover.
There is another option, though.
Unlike daisies, whose dead flower heads have relatively little structural interest, black-eyed Susans have dark seed heads that can be quite attractive through fall and winter.
Some people leave them standing throughout the winter for that structure.
And if you prefer to cut them back, you don’t necessarily have to do it right away.
As the stems dry out, they become dark and brittle. Sometimes, by late October or early November, you can give them a gentle push and pull, and they’ll simply snap off.
Otherwise, you can take your secateurs and snip them at the base.
By waiting, the plant and the weather have already done some of the work for you.
You can also leave everything until spring. This is especially useful if you have a very large garden, prefer a more natural appearance, or simply want to minimize the amount of work you do in fall.
Leaving the stems standing generally won’t harm the plant.
So there’s a range of approaches, from removing individual flowers throughout the blooming season to leaving the entire plant standing until spring.
Echinacea
A third plant in the Asteraceae family that I work with frequently is Echinacea.
Both Echinacea purpurea and Echinacea pallida produce quite substantial seed heads, which are well loved by local seed-eating birds.
If one of the purposes of your garden is to feed the birds, leaving the seed heads standing through winter is a good choice.
They also provide some structural interest in the winter garden.
So while cutting back daisies can reveal the plants behind them, and cutting back black-eyed Susans can create a lower layer of foliage, sometimes leaving a plant standing is the more useful choice.
It depends on what you want the garden to do.
A Follow-Up on Joe Pye Weed
Earlier this year, I wrote about trying a layered Chelsea chop on a Joe Pye weed.
A Chelsea chop is a cutback done earlier in the growing season, usually to delay flowering and encourage the plant to branch.
I made several cuts over a few weeks, at different heights, hoping to create a cascade of blooms rather than having everything flower at once.
The results were mixed.
The experiment did extend the flowering season, which was what I wanted. Instead of everything blooming at once, the flowers opened over a longer period, and I observed pollinators visiting the plant for longer.
However, something I hadn’t anticipated was how leggy the new growth would be.
At each cut, the plant produced about five new branches. But those branches were quite thin and lanky compared with the stout, sturdy stems that hadn’t been pruned.
From an aesthetic point of view, if I’d had something growing in front of the Joe Pye weed to hide the legginess, it might have worked quite well.
But as it was, I wasn’t entirely happy with the appearance.
It’s an interesting comparison with fall cutbacks because the technique is essentially the same. You’re cutting a stem at a particular height.
Earlier in the growing season, that cut can delay flowering and create a greater density of blooms. Later in the season, you’re cutting back to remove finished stems and prepare for winter.
The same action, at a different time, produces a different result.
A Garden That Changes Through the Season
Fall cutbacks don’t necessarily have to happen all at once.
You can take a layered approach, removing spent flowers first, then cutting back the remaining stems once the foliage begins to deteriorate.
Or you can wait until the end of the season, when the stems have dried out and are easier to remove.
Or you can leave them standing through winter and do your cleanup in spring.
These choices depend partly on how much time you want to spend in the garden, but also on how you want the garden to look and function.
What I find particularly interesting is how much the design can change without planting or moving anything.
A daisy can go from a flowering focal point to a mass of foliage, and finally to a groundcover. The turtlehead behind it becomes more prominent simply because the daisies are no longer occupying the same space above the ground.
The plants remain where they are, but their relationships change throughout the season.
And cutting back is one of the ways we can work with those changes.