Inspired by some recent posts by Thomas over at Grounded Design, I’ve been thinking a good bit about the gardening trends I’ve seen come and go over the past 25-plus years. I’ve enjoyed exploring many of them myself, and even those that now seem rather boring or impractical have left traces on the garden I have today.
Back in the early to mid-90s, for instance, when I was developing my previous garden, mixed borders were a hot topic at lectures and conferences, and I totally bought into the idea. Trying to incorporate shrubs into my plantings was a real challenge, though, because that garden was very small. Then, I started hearing about the great “new” idea of cut-back shrubs, and wow – that made all the difference. Who knew that there were shrubs that would tolerate being cut back almost to the ground each year? They’d give height and mass and winter structure, and it took only one simple pruning step to keep them from taking up too much valuable border space.
Well, it’s said that there are no new ideas in gardening, and this pruning technique, at least, was anything but new. Long known as “coppicing”, the technique has been used for centuries as a form of woodland management, and to promote the production of abundant, slender, straight regrowth that could be harvested regularly for firewood, fencing, and other uses.
I’d also run across the concept in my college plant-propagation class as technique known as “stooling” (or stool layering or mound layering): hard pruning as a way of encouraging woody plants to produce lots of new shoots that could be rooted in place and then removed. (If you’re interested in learning more about stooling as a propagation method, check out this excerpt from Lewis Hill’s Secrets of Plant Propagation for a more coherent explanation.)
Cutting-back also comes up when you learn about rejuvenation pruning, as a way of reclaiming overgrown deciduous shrubs. Not all them can recover from a drastic whacking, but if they’re otherwise healthy, cutting them back severely offers pretty good odds that they’ll resprout into a much fuller, better-looking shrub.
What was new about the concept of cut-back shrubs – to me, at least – was the idea of using hard pruning to create ornamental effects, rather than as a practical production or management technique. And while I’ve pretty much moved on from the hooray-for-mixed-borders mindset, having found that herbaceous borders are actually a whole lot less complicated to maintain, puttering in the garden this spring has made me realize that I still grow quite a few of the cut-back shrubs that I found so exciting back then.
If you too are a fan of colored foliage, you’ll appreciate the value of a maintenance technique that can produce bigger, brighter leaves. One of the best shrubs I’ve found for this is black elderberry (Sambucus nigra) – in particular, the relatively ordinary, yellow-leaved ‘Aurea’.
This golden elderberry clump in the front garden gets cut back hard at least once every spring. From a framework about 1 foot tall, it grows back to form a mound about 6 feet tall and wide, with broad, bright yellow leaflets that hold their color for months. It’s shown above in mid- to late July and at the very top of this post in mid-October.
One spring, I didn’t cut it back, and about a dozen of the long outer shoots sprawled and took root. The following spring, I moved the rooted layers to a transition area between the meadow and the garden. I cut these back only every three years or so, and they get 8 to 10 feet tall and wide. They stay bright into summer (they’re shown above in mid-July), but after that, the unpruned clumps look either bleached or greenish and are hardly noticeable.
Hard pruning is effective on cream-edged ‘Variegata’ and white-speckled ‘Pulverulenta’ too, as well as for purple-leaved cultivars. (Well, it did for ‘Guincho Purple’ in my old garden, anyway. So far, I haven’t had luck getting any of the purples established here.)
Coppicing for foliage works on red elderberry (S. racemosa), though I had mixed results with it on ‘Sutherland Gold’. In my old garden, I let it be a small tree, and it was lovely and lacy, even if mostly green after the first flush of fresh yellow leaves. I rooted two cuttings when I moved and decided to treat them as cut-back shrubs here, because I wanted to keep them in narrow spots. This one was in 4-foot-wide border out front (shown below in mid-June).
The other one was about 6 feet away from the north side of the house. It was very happy for a while (below is Year 3, in early July)
Unfortunately, both of them got weaker after each cut-back, and I lost the one out front after five years. I tried giving the other one a higher framework (about 2 feet), and even let it get a taller permanent trunk, but it lived only another two years.
It’s normally a beautiful shrub and I’d love to get another one, but if I do, I’ll keep my loppers off of it.
Smoke tree or smoke bush (Cotinus) is another woody plant that responds well to pruning for foliage interest. You give up the puffy flowers, but that’s a fair trade-off for the value of having the colorful leaves much closer to the ground. (Left unpruned, these shrubs or small trees reach the 15-foot range, with color mostly at the top.) I cut the deep purple ones – those sold as ‘Royal Purple’ or ‘Velvet Cloak’ – back to about 1 foot each spring, and that allows for some nice mingling with lower annuals and perennials from late spring through midsummer.
Later in the season, the shoots get quite tall (typically 8 to 10 feet), with the best color along the upper half of the stems. You lose the lower color combos, but the tall shoots still make a nice backdrop for tall fall bloomers.
Hybrid ‘Grace’ has also responded well to coppicing. The new growth is a rich red to reddish purple, depending on the lighting.
The color is less intense but still reddish to pinkish purple going into midsummer.
By late summer, the good color is mostly out at the shoot tips. Below is the same plant at the same time – mid-August – in 2008 and in 2010, showing the variation in the color it can have, depending on the weather conditions. But then you get the brilliant red fall color, so there’s still a benefit to having lots of bushy growth.
Golden catalpa (Catalpa bignonioides ‘Aurea’) is yet another candidate for the cutting-back technique, forming broad mounds of brilliant yellow to bright greenish yellow, heart-shaped leaves.
The garden effect is something like that of the golden elderberry but much bolder, because the leaves are entire and much larger.
Be warned, though: Keeping a golden catalpa (which wants to be in the 40-foot range) to border scale (6 to 8 feet tall and wide) isn’t a project you want to take on without serious thought. The same goes for princess tree (Paulownia tomentosa) – it too wants to be a big tree, and even with yearly coppicing, it can reach 15 feet or more, with gigantic, broad leaves.
Dappled willow (Salix integra ‘Hakuro nishiki’) isn’t nearly as vigorous as either golden catalpa or princess tree, but it can still get way too big for a home-scale border without severe pruning. I cut mine back to 6 to 12 inches every spring, and it fills out to about 8 feet tall and wide by the end of the growing season. Below is what it looks like in late May, about a month after coppicing.
A landscaper planted several of these at a neighbor’s place the same year. They never get pruned and are now about 12 feet tall and wide, with a rather ugly, rangy form. They also don’t provide a great show of this plant’s best feature: its brightly variegated new growth.
Unpruned dappled willow shows this mostly at the short shoot tips, and it seems to turn mainly green very quickly. On the pruned plants, the variegation stays bright through the summer and is still noticeable in fall.
Regular coppicing isn’t a pruning technique you’d use on most forsythias, because spring pruning removes the flower-bud-bearing stems, and you’d never get blooms. (Well, I suppose you could coppice immediately after the main bloom period, but I find it easiest to do all of my cutting-back at one time, so I’ve never tried it myself.) With ‘Kumson’ (Forsythia viridissima var. koreana), the flowers are nice but not nearly as interesting as the foliage. I have a few out in the shrubbery that I let grow as they wish. The summer foliage is still variegated, but it’s not nearly as bright or long-lasting as it is on new shoots.
I like to keep one piece as a foliage accent in a border, though, so I cut this clump back to about 6 inches each spring and enjoy the brilliant markings all through the growing season.
On deciduous shrubs that bloom on “new” wood (the stems produced during the current season), coppicing can produce larger flowers. Freakishly large flowers generally don’t do much for me, but I’ve gotten rather fond of the big white blobs of smooth hydrangea (Hydrangea arborescens) over the past few years. They weren’t my original goal when I started cutting back this row – I was mainly trying to control their size and shape – but since the regular spring pruning also led to the larger bloom clusters, it was just as well that I got used to them.
The trouble is, the larger the clusters, the more likely it is that the slender stems won’t be able to support their weight. Unless a dry summer keeps the shoots relatively short and sturdy, there’s a better-than-even chance that the blooms will end up sprawling at some point. Mine are planted only 3 feet apart, so they pretty much support each other, and there’s a fence along one side that helps too. When they keel over into the path, I cut them and stick them into watering cans and appreciate them as cut flowers.
Hard pruning has a similar effect on panicle hydrangeas (H. paniculata), such as ‘Limelight’…
These too have the potential to sprawl after hard spring pruning, but their regrowth seems to be sturdier than that of the arborescens types and better able to support the weight of the extra-large clusters, especially if you cut them a little higher – to a 12- to 18-inch framework – instead of right at or close to ground level.
Hard pruning also works beautifully on shrubs grown mostly for their colorful stems, because the young shoots also have the brightest bark. Shrubby dogwoods, such as Cornus sanguinea and C. sericea [C. stolonifera], are some of the best-known examples. ‘Budd’s Yellow’ has been vigorous enough here to tolerate coppicing every year.
Variegated ‘Silver and Gold’ tends to stay more compact, so I cut it back only every other year.
‘Sunshine’, with bright yellow foliage, has been the least vigorous of the three, so I coppice it only every third year, and to about 1 foot instead of 6 inches.
The red-twigged dogwoods don’t do well for me in general, but I am having good luck with coral-bark or scarlet willow (acquired as Salix alba ‘Chermesina’, which may or may not be the same thing as S. alba var. vitinella ‘Britzensis’, depending on who you ask). For a while, I was cutting it back every other year…
But now that it’s really settled in, I cut it to about 1 foot each spring.
I like ghost bramble (Rubus thibetanus ‘Silver Fern’) mostly for its foliage, but the white-coated first-year stems are interesting too, if a bit wild-looking.
It is so wickedly prickly that cutting it to ground level each spring is one of my least-favorite gardening chores. (Well, actually, the cutting isn’t nearly as bad as trying to figure out how to dispose of the tangle of ultra-prickly canes.)
I’ll add here that, as pretty as it is, ghost bramble is not a smart choice for planting close to a path. If you try to tip back the too-long shoots, it detracts from their graceful arching habit, but trying to cut them off at the base is a perilous prospect, even with long-handled loppers.
Pruning for size control isn’t directly related to creating ornamental effects, but it is an issue if you’re trying to keep foliage or flowering shrubs in the right scale as part of a mixed planting.
Ninebarks (Physocarpus opulifolius), for instance, offer some outstanding ornamental features (especially in the form of purple or yellow foliage), but the cute little starter plants that many nurseries sell can get way bigger than you’d imagine after a few years. They don’t seem to take kindly to a complete cut-back every year, but once they’ve been allowed to grow in place for several years, coppicing every second or third spring can be a good compromise. The plant will send up lots of dense, leafy, upright growth the first year.
The second year after cutting, it will start flowering again, as on this clump of Diabolo (‘Monlo’)…
…and produce the even-better red seedheads a few weeks later (below on Diabolo, at the back, and then on ‘Dart’s Gold’).
I don’t have much luck with butterfly bushes (Buddelia), but I do grow chastetree (Vitex negundo), and cutting-back works well for keeping both of these summer-blooming shrubs in reasonable dimensions for a medium-sized border.
If you’re thinking of trying coppicing in your own garden, I strongly suggest giving newly planted shrubs at least two growing seasons before you start cutting them back hard. Three or four years would be even better, unless you feel sure that they’re well settled in and growing vigorously. Consider cutting every second or third year for a time or two, then go to every year if a particular shrub seems strong enough to handle that. If you have established shrubs that you’d like to experiment on, try pruning to maybe 18 to 24 inches at first, then try out different heights and/or time intervals depending on how they respond.
I’ve found that, in a mixed-border setting, keeping coppiced shrubs vigorous enough to look good but small enough to not smother their companions is a continuing, but interesting, challenge, especially in the case of golden elderberry and golden catalpa. Both of these have been so vigorous that, a few years ago, I resorted to cutting them back twice each spring. On the golden elderberry, I let it leaf out about halfway…
…then cut it back to about 1 foot in mid-May.
I let it shoot up again, then cut it back to 2 to 3 feet about a month later (early to mid-June).
On the down side, the cut-back plant looks rather ugly much of the time until about midsummer, which would be unfortunate if I planned my borders for spring and early summer. But since I like having them peak in late summer and fall, the two-cut approach has been a great way to get a real jolt of bright color and fresh-looking foliage while keeping the elderberry about the right size.
I treat the catalpa in a similar way, but it’s on a three-stem framework that’s about 18 inches tall.
I let it leaf out once…
…then cut it completely back to the framework in late May. (It’s the clump of bare trunks on the right, with a cut-back ‘Dart’s Gold’ ninebark in the middle and a cut-back ‘Grace’ smoke bush on the left.)
When it leafs out again (mid-June, below)…
…I break or prune off half to two-thirds of the new shoots. And if the clump got really large the previous year, I cut the remaining shoots back yet again, to about 1 foot above the framework.
As with the golden elderberry, all this pruning makes the golden catalpa kind of ugly until about late July, but then it’s lovely for late summer and fall.
One more tip I can share relates to keeping a higher framework for the coppicing, as I do on the catalpa, and on ‘Grace’ smoke bush too. It looks rather bizarre during the off season, but it lets you plant closer to the base of the shrub. I’ve had the best luck with either early bloomers, such as hellebores, or tall fall bloomers, such as burnets (Sanguisorba), ironweeds (Vernonia), and sneezeweeds (Helenium), which can grow up through the outer branches of the shrub and use them for support.
To show a bit more detail of the pruning, here’s what ‘Grace’ looks like in March:
I cut the thicker stems to short stubs…
…and snip out all of the tiny twigs…
…to get a clean framework.
Here’s the new growth in early May…
…and the same shrub three weeks later.
Well, gee, this post got way longer than I expected, and I hope I haven’t made it all more complicated than it really is. Coppicing may not be a comfortable technique to use if you’re timid about pruning, but if you’re not afraid to do some serious lopping and you have some shrubs to experiment on, give it a try and see what you think!