Pruning Trees and Shrubs

Why prune at all?

Pruning ShrubPruning is necessary for most plants to get the best from them. There are several reasons to prune and it is well to focus on why you are cutting away at your plant in order to get the results you want.
• Pruning stimulates new growth in a plant.
• Pruning reduces or maintains the size of a tree or shrub
• Pruning removes dead, diseased or broken branches
• Pruning stimulates flower and fruit development
• Pruning old, established trees or shrubs helps to rejuvenate them
• Pruning decreases danger of injury and/or damage to property
• Pruning can shape plants into a sculptural or architectural form
• Pruning improves air circulation within and around a plant

Pruning re-sizedTerminology: Here are some terms that are often thrown around in texts about pruning
Apical– The adjective for apex; on a tree or shrub the apical shoot grows upward
Crotch– Area between trunk and a main limb
Lateral–A shoot or branch growing sideways from a stem
Leader– Main upward limb on a tree or pyramidal shrub
Scaffold Limb– Large limb that forms the framework of a tree
Root Sucker– Shoot arising from the root system
Spur– A short shoot that bears flowers and often fruit
Water Sprout– A long shoot that grows in an undesirable location on the trunk or a major limb

Pruning Tools

It is pretty hard (and quite frustrating) to prune without the proper equipment. Here is a short list of useful pruning tools.

Floral and Garden scissors: Good for cutting flowers and small branches, also for trimming topiaries

Bypass pruners: The blades work like scissors and do less damage to the stem than anvil pruners; good for cutting small branches and stems

Loppers: Pruners with long handles which give you better leverage and longer reach to cut larger branches

Shears: Giant scissors used for shaping formal hedges; also great for cutting back perennials

Saws: Good for cutting large branches; pruning saws include hand held saws, folding saws, bow saws, pole saws and chain saws (really really know what you are doing with a chain saw or just don’t touch one, OK?)

Whatever you use, keep it sharp. Cutting with dull pruners will quickly bring you to tears.

What happens when we prune?

Some understanding of the biology of a plant will make decisions about what, when and how to prune a lot easier. Every branch or stem has a terminal bud, the bud that is at the very end of the stem. This bud produces a hormone (auxin) which suppresses the growth of the other buds, called lateral buds, along the stem. If you cut off the terminal bud the lateral buds closest to it will begin to grow vigorously. The most vigorous new growth always occurs within 6 to 8 inches of the pruning cut.

Whenever you cut a branch, the plant immediately begins to heal. The hormones that help heal wounds are most highly concentrated at the lateral buds and where each branch joins a larger branch or the trunk. When you leave a stub, the distance from the hormonal source increases and the wound heals more slowly, if at all. Insects and diseases may enter the cut portion of a stub and cause it to die back.

Two areas on the tree or shrub — the bark ridge at the junction of two limbs, and the branch collar where the lateral branch joins the main limb will eventually close off the wound between the plant and the pruning cut. For fastest healing, prune close to the main branch without injuring the bark ridge or branch collar areas.

Types of pruning

Pruning falls into two major categories — heading and thinning.  Heading basically cuts off the ends of branches. It can range from a light snipping of your spirea to give it a more even shape, to creating a formal hedge, to whacking back your crapemyrtle to stubs. The technical term for this last, by the way, is pollarding. It is also sometimes called ‘crape murder.’ Heading, as you remember from our little biology lesson, will stimulate lateral branching, causing the plant to become thicker.  Thinning involves cutting branches back to a larger branch or to the base of the plant. Thinning cuts can reduce the size of the plant, give it a more pleasing shape and allow better air circulation without changing the basic natural shape of the plant. And unlike shearing, it doesn’t cause to plant to grow tons of new branches.

When to Prune

Most plants can be pruned lightly any time of year. Certainly you don’t want to delay cutting out diseased or dead branches. Otherwise, when to prune depends on why you are pruning. If you are working on the basic shape of a tree or shrub, especially a deciduous plant, winter is the best time. The tree is dormant and you can see what you are doing. If you are controlling the size of a plant, any season is fine except for fall. Here in the South, fall is the worst time for pruning because all the new growth you stimulated (remember our biology lesson) will be promptly burnt up by the first frost. When pruning a flowering plant, however, you want to take care you do not interfere with the flowering. Each plant is different, but the main question to ask is ‘Does it flower on this year’s new growth or on last year’s growth?’ If it flowers on new growth, cut it back in the winter to stimulate new shoots and get rid of old ones. If it flowers on last season’s growth, wait till it finishes flowering and then prune if you need to.

This is a list of some common plants and when to prune them.

Prune After Flowering Prune Before Spring Growth Begins
Bigleaf Hydrangea
Bradford Pear
Bridalwreath Spirea
Climbing Roses
Doublefile Vibernum
Flowering Almond
Flowering Cherry
Flowering Quince
Japanese Kerria
Japanese Pieris
Oakleaf Hydrangea
Saucer Magnolia
Star Magnolia
Shrub Honeysuckle
Thunberg Spirea
Vanhoutte Spirea
Winter Daphne
Goldenrain Tree
Chaste Tree (Vitex)
Cranberrybush Viburnum
Floribunda Roses
Fragrant Tea Olive
Glossy Abelia
Grandiflora Roses
Japanese Barberry
Japanese Spirea
Rose-of-Sharon (Althea)
Anthony Waterer Spirea

Pruning to Regenerate old Overgrown Plants

Sometimes things get away from us or sometimes we inherit someone else’s problem. For whatever reason, we are faced with an overgrown monster that is swallowing our house, walkway or yard. What to do?  Well, it depends on the monster.

Overgrown conifers such as junipers, arborvitaes, cypress and such are difficult to remediate because they generally grow only at the tips. If you cut back into the older branches they generally do not regenerate. You can sometimes limb them up or top them, but many times the only thing to do is remove them.

Broad leafed trees and shrubs are easier to fix by either of your two basic pruning methods, shearing or thinning. Some stalwart shrubs such as hollies, ligustrums, wax myrtles, nandinas and the like can simply be pruned back close to the ground and allowed to regrow.

Other shrubs can be tackled by thinning them over a period of three years. Choose the oldest gnarliest ugliest stems and cut them to the ground. Take no more than a third of the plant. Next year take another third and the third year remove the remaining old branches, leaving an entirely rejuvenated plant.

Pruning really isn’t rocket science and observing a few basic rules will allow you to keep your yard in control. And take heart. Most plants are very forgiving and even terrible mistakes will disappear in time.