Pruning Basics: Why, When, and How to Prune for a Healthier Garden
Pruning isn't just about aesthetics – it’s vital for plant health. Learn how, why, and which way to prune to ensure your garden grows the best it can.
What is pruning? It's a simple question, but one that can have a lot of different answers. At its most simple, pruning is simply cutting off parts of a plant. There are many reasons to do it, though, and even more ways to go about it. The process can feel overwhelming when you aren’t familiar with it.
In this article we'll go over the main reasons for pruning, the different kinds of pruning tools, and the actual, practical ways to go about pruning a tree, shrub, or other plant.
Reasons for Pruning
Responsible pruning is always done for a specific reason. Here are the main ones.
Article continues below1. The 3 D's
Every pruning session should begin by identifying the Three D's: Dead, Damaged, and Diseased tissue. If you're pruning a tree, removing dead or broken branches is a safety priority – the last thing you want is for a limb to fall and hit a person or a building. There's also the chance that it could strip away a large chunk of bark with it, seriously hurting the tree.
If you're dealing with disease, it's vital to cut below the infection and well into the healthy tissue, and to sterilize your pruners between each cut. Never compost diseased material – you'll just be spreading the pathogens around your garden. Instead, bag them up and dispose of them in the trash.
2. Rejuvenation
Removing older, unproductive branches is a good way to refresh or rejuvenate a plant that hasn’t been trimmed in years.
If you're pruning a tree, it's vital that you never take off more than 1/3 of the canopy in any one year. This can kill the tree! Instead, think of it as a three-year project – remove 1/3 of the old growth each year, while allowing new, healthy growth to take its place.
This is also referred to as "stagger pruning," and it's vital for nesting birds.
For certain shrubs and perennials, rejuvenation pruning can call for a much tougher approach. It's called "hard pruning," and it involves cutting every stem down to the ground. A lot of plants will bounce back from this, but many may not flower for a year or two after. Some plants that actually benefit from hard pruning are:
3. Aesthetics
Finally, pruning can also be done for aesthetic purposes, to shape a tree gracefully, even up a hedge or open up the center of the canopy to sun and air. Some people also enjoy pruning a shrub into a particular shape, like an espalier or a topiary.
Tools of the Trade
Before you make the first cut, it's important to have the right tools for the job. I once cut back an overgrown star jasmine that was taking over the side of my house with... a pair of scissors. It took forever and my hand ached for days. Don't be like me.
For stems up to 3/4 inches (2 cm) thick, bypass pruners are the gold standard for clean, quick-healing wounds. They work like scissors but, importantly, are designed to actually cut through woody stems.
For thicker branches up to 2 inches (5 cm) in diameter, you'll need something bigger. Loppers have long handles that provide much more leverage than a small pair of pruners.
If you're dealing with larger branches, you'll need a pruning saw – its serrated teeth can cut through wood of any thickness
Once you have your tools, it's vital to take care of them. Keep your pruners sharp! A dull blade won't make a clean cut. Instead it'll crush the plant tissue around the cut, leaving the plant vulnerable to disease. And as anyone who's cooked with an old knife can tell you, dull tools are dangerous! One slip could turn your day of yard work into a day at the emergency room.
Hygiene is just as important. Pruning cuts straight into a plant, meaning whatever was on the blades of your shears now has direct access to the plant's core. You should always sterilize your blades with 70% isopropyl alcohol or a 10% bleach solution when moving between plants. This prevents the accidental "hitchhiking" of fungal spores or bacteria from a sick plant to a healthy one.
Think of it this way – if you were having surgery, you'd want your surgeon to wash their hands between you and the last patient. Wouldn't you?
When to Prune
Before you start pruning a tree or shrub, consider when to prune. Most plants can be pruned at any time of the year without putting their lives at risk, but some are best pruned at particular times.
Needled evergreens can be pruned at any time of the year, but spring pruning helps keep the plants compact. Some deciduous trees, like birch or dogwood, have a strong sap flow in early spring and “bleed” when pruned in spring. Prune those in summer or winter to avoid that sap loss.
Trees or shrubs that flower in spring should be pruned right after they flower, but prune summer-flowering trees in late winter. This ensures that you won’t cut off next season’s buds. If you love a shrub’s fruit display, wait until after the fruit is harvested to prune.
How to Prune
There are many different types of pruning you can try, but three simple pruning techniques will cover most situations: pinching, thinning and heading back.
1. Pinching
Pinching means removing the soft, growing tip of a stem with your thumb and forefinger – literally pinching it. This signals the plant to stop growing tall and start growing wide, resulting in a bushier appearance.
2. Thinning
Thinning cuts remove some of the branches in a tree, taking them out at the trunk. You should do this cut if you want to remove a branch completely.
Make the cut an inch or two from the main stem, leaving the branch collar intact. Removing the branch collar (the swollen area at the base of the branch) encourages infection. This is because the collar contains the cells necessary to seal the wound.
3. Heading Cuts
Heading cuts are sometimes called reduction cuts. They involve cutting branches about ¼ inch (0.5 cm) above a bud or lateral branch. This will encourage the branch to grow out, perpendicular to the main branch to create a thicker, bushier structure. You should choose this if you want a branch to continue growing, but in a different direction.
