The City Gardener: Perfect pruning for perennial perfection

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Mid- to late April is the perfect time to prune away dead and broken branches

I read somewhere (probably in one of those bracing, old-fashioned English gardening books) that the best time to prune is when your secateurs are sharp. In other words, you can prune just about any time of year that your garden is actively growing.

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While that may be true, I think that now, just as the new gardening season gets underway, is the perfect time to get this somewhat labour-intensive but critical process done.

In some ways, this is my favourite time of year to work in the garden. Mild, sunny days are getting more frequent, and you can spend some quality time outside without your fingers and face stiffening from cold and wind.

And it’s great to say hello again to neighbours walking by, after we’ve all been huddled inside our homes for so long.

A basic pruning kit includes three tools: secateurs, the fancy name for the handheld pruners that no gardener can do without; loppers, which come in different sizes; and a folding pruning saw, strong enough for branches that are too thick for your loppers, but too small to pay a tree company to remove.

Buy a sharpening stone or some other sharpening tool, and make sure your tools are razor-sharp each time you use them. Dull tools are not only harder to work with but can damage the plant. Clean them well with WD40 or soap and water after each use.

Examine the shrub and look for dead, weak or broken branches, and any that cross over another branch or are growing in a weird direction. Trim using what’s called a heading cut, where you trim the branch at a 45-degree angle, no more than a quarter-inch above a bud or fork that faces outward.

If you’re cutting back flush to a larger branch, trim as close as you can get without actually cutting into the flesh of the main branch, leaving the knot (or “collar”) intact.

The traditional technique of using hedge clippers (or a power hedge trimmer) to square off boxwood, cedar, spirea and other hedges has its place, especially in formal gardens (not to mention Edward Scissorhands-style sculptured topiary).

But this can cause the interior of the shrub to die off over time, leaving just a shell of leaves and flowers. If you want a more natural look – and especially with single specimens or small groups – you’ll want to prune more selectively, using the same heading-cut technique. Prune interior branches as well, letting air and light into the interior of the shrub.

While most of the time you don’t want to get too carried away with the clippers, some plants periodically benefit from a process called “hard pruning”: lopping the whole thing off cold about six to twelve inches from the ground, so it can start all over again.

I do this with my ‘Jackmanii’ clematis every April, and while purists might fault me for it, I find that not only does the plant immediately start sending up new shoots, by June it’s blooming its head off. Besides, it’s the only way I know of to clean out last year’s dead vines. (If you know a better way, write to me and let me know!) You can also do this with ornamental grasses, lavender and some vines like wisteria.

With early-flowering shrubs like forsythia, it might be better to hold off until they’ve finished blooming so you don’t accidentally cut off flowering branches. (Although here’s another exception: as soon as your forsythia starts to set buds, cut a handful of two- or three-foot branches, bring them inside and put them in water, where they’ll bring a sneak preview of spring to your dining table.)

Please feel free to write in with questions, to comment or to share your own city gardening
adventures with Martha. Write to her at marthasgarden07@gmail.com.