Pruning Basics

What is it that causes humans to want to carve shrubs into unnatural shapes? No matter – behind mowing the lawn and watering potted plants, pruning is arguably the third most common gardening activity, based on how many gardeners take up loppers and shears and have a go at it.

Cutting plants willy-nilly or improperly can destroy their natural shape, lead to decay and even the death of a plant, and cause neighbors to talk. Still, it’s sometimes a matter of style and preference, no more unnatural than, say, plucking eyebrows or shaving. Still, damaging a plant with cutting tools without good intentions should be avoided. 

Over the centuries we have come up with some really good reasons to prune plants, both practical and aesthetic. The most common are to keep large plants safely within bounds, to train and keep plants in practical or interesting shapes (think hedges, and topiary), to keep some plants more floriferous or fruitful, and to remove dead, diseased, or wayward plant parts. And of course there are many, many variations.

Practical Examples

The most common pruning done with landscape shrubs is usually our attempting to keep shrubs neatly in bounds, especially when large shrubs are planted where medium or small shrubs should have been planted in the first place. Repeated shearing of new growth on plants keeps them compact and stimulates of fresh new leafy growth for a more dense effect. Barrier or privacy hedges - rows of closely-spaced plants – can generally trained into flat “living walls” by shearing new growth once or twice a season.

Roses, Buddleia (butterfly bush) and other summer-flowering shrubs can be kept more vigorous and floriferous with annual pruning. Repeat bloomers are usually pruned hard in midwinter (to a couple of feet tall) and again lightly in midsummer;  azaleas and other shrubs and vines that flower only once in the spring are pruned by cutting them back in late spring or early summer. Like most other flowering vines, climbing or “running” type roses are merely thinned as needed to remove old or wayward canes, leaving most stems unpruned.

Most fruit trees and shrubs, and grape vines, are nearly always best kept shaped into relatively small, open-branched plants that are easier to care for and harvest; while this may limit the potential fruit load, it encourages larger, better quality fruit on sturdier plants more able to support what is left. It also targets the removal of cluttered, diseased, unproductive limbs and branches.

Where there is room to grow upward, large shrubs normally sheared regularly into tight, overgrown meatball shapes can be “limbed up” into small, more natural-looking trees by removing a few lower limbs, then thinning a few branches from those that are left. Afterward, the plants will require less regular pruning.

There are several oft-misunderstood pruning techniques used by horticultural or hobby gardeners, particularly topiary, bonsai, espalier, and pollarding, all of which create and maintain plants in very unique shapes. 

Topiary just means pruning plants into different, often fantastic shapes; espaliering a plant means training it to grow flat against a wall or fence by removing outward-growing twigs and branches. Bonsai is an artistic approach toward keeping plants very small and miniature, sometimes for decades. 

Pollarding is simply cutting stems of shrubs or trees back every year to knobby balls, which is an age-old practice used to produce lots of uniform, supple stems for weaving into natural “wattle” garden fences.

Note: Despite shrill public comments from the “my way only” crowd, it does not harm a plant to be pollarded! While often criticized as unnatural - when applied to crape myrtles, it is referred to as “crape murder” - it is technically no more damaging than any other regular pruning. However, it is not a good idea to “flat top” huge limbs on mature trees, which can lead to long term decay. 

Do and Don’t

Removing dead, diseased, or dangerous growth can be done any time of the year; however, in general it is best to prune plants at a time when flowering or fruiting is not affected, or when not so close to winter that new growth won’t have time to “harden off” before winter. The best general rule of thumb for this is to prune spring-only flowering and fruiting plants after they bloom, then leave them alone; prune summer- or repeat-blooming plants in winter, with perhaps a second light mid-summer pruning. And be done with it at least a couple of months before your first expected frost in the fall. By the way, many winter-berry plants such as hollies are spring bloomers; pruning hard in the spring or summer can remove berry-making growth. Wait until berries form in summer to decide what to prune and what to leave. 

Remove large branches or limbs in a way that keeps them from stripping bark off the trunk as they fall. Make a small cut underneath, an inch or so deep, close to the trunk, then make the main cut from the top, a few inches farther out, so bark stripping will only go as far as the “undercut.” Make a third cut to remove the stub to make it nearly flush with the trunk, which speeds up healing and reduces decay caused by insects or wood-rot fungi. Don’t leave stubs!

There is one other caveat about pruning, concerning “conifer” type plants such as juniper, cedar, fir, arborvitae, and the like: unlike “broadleaf” plants, most of which can sprout new growth from even very old bare branches, if you cut a conifer branch or limb back beyond where it has green leaves or needles, it won’t sprout back out; instead it will die all the way back to whatever it grows off, be it another limb or the trunk.

Lastly, don’t fall for using gimmicky “pruning paint” which is purely cosmetic. Use it only if you think it will make someone else think more highly of your pruning expertise. Meanwhile, think before you cut – then have at it!