I wish I were as pliable as most plants. Confronted with obstacles to their growth, they can duck, dive, weave, bend, stretch, twist and regenerate at will. Plant a sun-loving climber in a shady spot, for example, and it will reach towards the light. Stick a willow tree in a dry corner, and its roots will roam far and wide in search of water. Allow a wallflower seed a small crack in a sunny pavement in which to germinate and grow, and it’ll do exactly that, anchoring its root systems into the stony ground without protest.
That same resilience is evident in plants’ response to physical injury. Cut their stems and branches back – even their root systems – and these will usually regrow, just not in the very same way as before.
This remarkable ability to regenerate is something that gardeners have traditionally used to our advantage in a multitude of ways. We can make a plant bushier, for example, by “pinching out” or removing the uppermost tip (properly known as the “apical bud”) of the main stem. The result of this sort of formative pruning is a series of rapid hormonal changes which promote the development of lots of side shoots instead of vertical growth, causing the plant to “bush up”. It’s what happens when we trim a young hedge, pinch out the growing tip of a seedling, or give summer-flowering perennials the Chelsea Chop.
Likewise, we can selectively prune a plant in such a way that it deliberately stimulates growth in a particular direction by, for example, making the pruning cut just above a particular bud that we’ve intentionally chosen for its position on the stem. In this way, gardeners can heavily influence a plant’s growth habit and thus its size and shape.
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Why bother? For lots of good reasons. For example, prune the branches of a young fruit tree in the right way, at the right time of year – a process known as “formative pruning”– and you can potentially train it into an astonishing variety of decorative shapes. Good examples are espaliers, stepovers, fans, cordons, which help to make your tree much more space-efficient, as well as productive.
Careful timing when pruning is key to avoiding plant shock to elderly specimens (even plants have their limits)
The same goes for many kinds of ornamental woody shrubs, from witch hazel, wintersweet, silk tassel bush, chaenomeles, fuchsia, pyracantha and bull bay to forsythia, ceanothus, ribes, climbing roses, wisteria, and abutilon. All can be trained with carefully targeted pruning to grow neatly against a wall, greatly reducing their bulk without compromising on their decorative qualities – a huge advantage in smaller gardens.
Likewise, both crown-lifting and crown-thinning of trees is another way in which pruning allows us to manipulate their size and spread. So is taking a sharp garden shears to small-leaved evergreen hedging species such as box, yew, Japanese holly, shrubby honeysuckle and phillyrea to shape them into the most fantastical yet space-efficient of forms.
Regular annual pruning can also prevent mature woody plants from becoming overgrown, and helps to make them more floriferous and productive. In this case the aim is to remove all dead, damaged and diseased branches as well as any spindly or crossing branches, along with a percentage of the oldest growth, stimulating the production of lots of new, strong, healthy shoots. If you’ve ever pruned a rosebush in this way, then you’ll have seen the results in the shape of a healthier, happier, more floriferous plant. The very same goes for hedges as well as most fruit trees and fruit bushes.
Annual pruning is also recommended for many other kinds of established ornamental deciduous shrubs, including weigela, philadelphus, spiraea, forsythia, kerria, buddleia, hydrangea and abelia. But again, careful timing is key to avoiding plant shock to elderly specimens (even plants have their limits), as well as to avoid disrupting their flowering and fruiting schedules.
That timing varies according to the particular species and can be confusing, with the Royal Horticultural Society dividing plants into not one, not two, but 22 different pruning groups (rhs.org.uk). Roses take up eight of these – proof of how vast this genus of ornamental plants is.
For plants in some of the remaining 16 groups (for example, rhododendron, camellia, fatsia, eucryphia, hebe, arbutus as well as Japanese maple, lilac, flowering dogwood, snowy mespil and magnolia), little or no routine pruning is recommended.
Whatever the plant, bear in mind that good pruning techniques also require good tools
At the other end of the spectrum is the minority of plants that respond very well to being pruned back extremely hard every year, rapidly producing an abundance of new growth. Examples include paniculate hydrangeas (cut stems back to just above the lowest bud in spring) and late summer-flowering Clematis viticella (cut back to 15cm-30cm and just above a set of healthy buds in late winter/early spring). Confusing? Yes, it can be, which is the reason why a garden diary with a monthly list of any pruning needed is a great way to keep track of what’s required.
Whatever the plant, bear in mind that good pruning techniques also require good tools. If you can, invest in a quality secateurs, a loppers and for thicker branches, a strong but lightweight folding saw (see the Silky range on knivesandtools.ie), and keep them dry, clean and sharp. Thick, waterproof, protective gloves are also a must if you’re dealing with thorny plants (those same thorns, by the way, are yet another example of nature’s endless ingenuity). Finally, a handful or two of slow-release organic fertiliser and a generous organic mulch around the base of the plant after pruning is also recommended.
[ Sculptural evergreens to keep your garden beautiful through winterOpens in new window ]
This week in the garden
The following deciduous flowering shrubs should be given their annual pruning between early February (milder areas of the country) and mid-March (colder parts): Hydrangea paniculata, ceratostigma, lavatera, perovskia, hardy fuchsias, and Buddleja davidii.
February to early March is also the best time to cut back vigorous climbers such as Virginia creeper, Boston ivy, ivy (Hedera) and ornamental vines. Wisteria should also be given its winter pruning in the weeks ahead by cutting shoots back to two-three buds from the main framework of stems.
Dates for your diary
RHSI Snowdrop Weekend RHSI Bellefield Gardens, Shinrone, Co Offaly; Friday, February 6th-Sunday, February 8th (11am-4pm), admission free for RHSI members, €8 for non-members, see rhsi.ie.
Post Industrial Landscapes: A New Greenspace, an illustrated Zoom talk by UK gardener and designer John Little on behalf of the RHSI Wednesday, February 11th,see rhsi.ie.
The Interconnection Of All Things, this year’s GLDA Seminar, Crowne Plaza Dublin Airport Hotel Conference Centre; Saturday, February 28th. With guest speakers including plantsman and historic gardens consultant Neil Porteous, British environmentalist and inventor Galen Fulford, US landscape designer and author Margie Ruddick, and British landscape designers Lulu Urquhart and Adam Hunt. Tickets €70-€170, see glda.ie.
