One of my favorite gardening tasks is pruning. In fact, I love it so much that I don’t really consider it a task at all, and it was the focus of my very first The joe gardener Show podcast episode. Unfortunately, it’s a subject that tends to confound or intimidate many gardeners. Today’s guest, Steve Bradley, was determined to break the sometimes confusing principles of pruning down to the basics, and his book, The Pruner’s Bible, does just that.
Steve is a popular gardening expert in his native Great Britain and beyond. A degree in education, combined with the prestigious RHS Master of Horticulture degree, led him to a thirty-year teaching career. He’s also a frequent lecturer and host of radio programs throughout the U.K. on the BBC. I’m not sure how he found time to write, but between the two of them, Steve and his wife (also a horticulturist) have over 50 books to their credit.
With detailed instructions and clear illustrations for pruning approximately 70 common plants along with guidelines to help any gardener understand key principles, The Pruner’s Bible takes the fear out of making those all-important cuts.
As gardeners, what we most want to see is growth. That’s why pruning can often feel counter-intuitive. We see growth as a sign of success and health, so why would we ever want to cut it off? I also hear from lots of gardeners who are worried about killing a plant by pruning, but the truth is that pruning encourages more growth and improves plant health.
A cut to a branch causes a chemical response, triggering a plant to develop new foliage and branching. Pruning also improves overall plant health as we manage its structure and size. Just as importantly, it’s how we can guide a plant to do more of what we want it to do.
Basic Pruning Guidelines
Steve’s most basic rule for pruning can be applied even when you have no idea what type of plant you are dealing with. If it flowers between Christmas and late summer, the plant should be pruned right after flowering is finished. Any species which flowers between late summer and Christmas should be pruned the following spring.
Cold winter temperatures can take a natural toll on areas of any plant. A cut made before late summer still allows the plant time (before winter sets in) to grow and set new flower buds for the following year. The sooner after bloom you can prune, the longer the plant will have to develop new growth. A late-blooming plant won’t have time to develop new flower buds before winter.
As with all things, there are a few exceptions to that timing. Hydrangea and clematis are examples of plants which are more particular about pruning schedules.
Oftentimes, you’ll hear advice that the best or only time to prune is in early spring, before any growth emerges. That’s an effective strategy (particularly for non-flowering shrubs), but it’s also helpful to feel free to prune during those post-bloom periods – when you can actually see how the branches look together while in full foliage.
Steve is often sought for his advice on pruning, but the best tip he ever received was to pause and observe the plant. It will often give you clues on where to make the cuts.
Even if you don’t know what species a plant is, observing the clues a plant will provide you can guide your pruning in the right direction. If you’re unsure how to get started, spend a year observing what the plant does – how it grows, when it blooms, etc.
For example, most flowering shrubs only bloom on the same wood once. In other words – once a branch has flowered, it’s not likely it will bloom on that branch in future seasons. So, a branch with spent flowers is a good candidate for removal to make room for more branches to develop which will eventually bloom.
What if you make a pruning mistake? Fortunately, plants are very forgiving and will almost always bounce back within a couple of years. In fact, the worst mistake you can make is to let a plant go too long without pruning. Eventually, that plant will grow out of control, and overgrowth encourages disease or pest infestation.
There are a few cuts you should make at any time of the year and regardless of your goal for the plant. The four D’s should always be a priority for removal:
If your plant has an area that is dead, dying damaged or diseased; remove that area as soon as you can. During regular pruning, remove those areas first too. Then, take a step back to view what you are left with and think about your goals for the plant.
Pruning really is part science and part art. So before you make the first cut, spend that time in observation. Then, decide what your goal for that plant is. Do you want more growth? Do you want to encourage fruit? What would you like it to look like once it’s mature? The goal you set will guide you to make the best cuts.
To quote Steve, “It’s not so much knowing how or where to cut but what you are trying to achieve.” I love that advice. So instead of worrying that the cut you make will do harm, look at pruning from a different perspective. Pruning is an important part of the gardening experience.
Steve breaks the main reasons to prune into 7 categories:
- Balancing Growth
- Controlling Flower & Fruit Quality
- Creating a Pattern of Growth
- Maintaining Plant Health
- Restricting Growth
- Remedial Pruning
Let’s take a closer look at each of those and how you can put them into practice.
Training Your Plant
No matter what you plant in your landscape or garden, there is something you intend for that plant to do. Whether you hoped it would provide privacy, produce fruit, bloom, become a focal point, etc.; your dream for that plant can and should be guided through pruning.
Steve says pruning is a little like raising children. If you don’t set your kids up for success during their early and formative years, you will wind up with problems down the road. It’s important to guide your children to grow in the right direction. Pruning does the same for young plants – with a lot less argument.
When you prune a young plant, you are creating the framework or architecture of the plant in its mature stage. For example, do you want a tall plant with smaller branches radiating from a single, main stem? Would you prefer a wider, shrub-like shape with multiple, spreading stems? The best time to train your plant for those structural options is during its early growth period.
If your goal is a plant which will spread along a wall or to obscure an eyesore on your property, the earlier you can begin training the plant to grow in those directions, the better.
Fruit-growers call this Formative Pruning. It’s common to train a fruit tree to grow in an Open Center, Central Leader or other form for a very specific purpose – such as encouraging fruit or to make harvesting easier. Professional fruit growers intentionally shape a young tree for a number of reasons.
An Open Center form (shaped like a wine glass) is one of the most common. It encourages more light to reach the center branches (for better fruit production and ripening) and more airflow to reduce pest and disease risk.
This formative or training pruning can be important for the overall health of the plant too. By pruning for good branch angles (45-60 degrees), the tree or plant will be better able to support the weight of heavy snow and ice.
While you’re training your young plant, observe how the growth responds. That will train you to become more comfortable with making those cuts
As a plant matures, maintenance pruning can help to balance growth. As seasons pass, pruning to balance growth will influence how heavily a species will bloom, produce fruit, set foliage, etc.
Deadheading (or what Steve refers to as “rooting”) is a good example. Many plants will cease to grow if their spent flowers aren’t trimmed off – deadheaded. So, this single and simple act will keep an ongoing balance of bloom and growth.
If you’ve ever grown lilacs, you know that they bloom on the end of a branch. Once the flower fades, it turns into a woody little mess of seed pods. It’s not until that spent bloom or woody remains is cut off that the lilac shrub is triggered to produce new shoots for future branches and blooms.
Have you ever noticed that marigolds become lanky and dull unless you pinch off spent flowers through the summer? That’s pruning to balance growth and a good example of deadheading.
It really is remarkable how plant tissue responds to the how, when and where a cut is made. Researchers found that pruning an apple tree branch once it had produced 21 leaves triggered chemical changes which caused the tree to set more flower buds for the following season. If the branch was pruned when there were less than 21 leaves, the tree generated more foliage and branch growth – instead of the flowers which would later fruit.
Most plants don’t require such precise timing. That’s a good thing since we don’t all have the time or patience to wait until the 21 leaf mark. More often than not pruning to balance growth is simply removing the four D’s mentioned earlier (dead, dying, damaged, and diseased), a few cuts to maintain the shape you prefer.
Controlling Flower & Fruit Quality
Not only can you control the quantity of fruit or flowers that a plant produces, you can also encourage better quality through your pruning choices. When and how you prune can each play a role.
Steve gave the example of butterfly bush. The initial flower spikes that pop up tend to be a little nicer than the blooms that follow, but you can get the showiest blooms with a timely pruning. Cut out the initial spikes right as they start to fade. That encourages the second round of blooms to be larger and more vibrant in color.
Butterfly bushes tend to have vigorous growth, but it’s supported by a brittle root system. So, Steve cuts them back to about half their height in early winter in order to prevent them from being knocked over by the wind. In early spring, Steve gives the shrubs a harsher cut to no more than a foot high to encourage them to produce vigorous upright growth in the season ahead.
Crabapples will provide more and better quality fruit when the thin, wispy growth they tend to produce is removed out of the center branches of the tree.
There are other examples in Steve’s book, but once you begin to grasp the basic principles, you can apply them to all the species of plants in your landscape. Don’t be afraid to experiment. If you take notes and observe the results, you just might discover something outstanding.
Creating a Pattern of Growth
It’s important to train plants during early growth, but you may not always have that option. There are some plants that don’t produce the effect you want unless you trigger a particular response each season. These are situations when pruning to create a pattern of growth will help you achieve your goal.
Hedges, for example, can be trained early on, but they will still require ongoing pruning to encourage them to grow in a hedge form. The brilliant red of ornamental dogwood will fade unless you prune back to around ground level every year to trigger a flush of new, richly-colored growth.
Smoke bush and hazel trees respond very differently, depending on how they are pruned. These plants will produce showy, leaves when they are pruned back harshly. That’s a bonus for any gardener who enjoys the look of eye-popping foliage or uses stems for decorative purposes. On the other hand, gentler pruning of smoke bush will encourage more flowers. So if you’re looking for bloom, stick with deadheading only, and avoid removing large areas.
Maintaining Plant Health
This type of pruning is important for creating space for air and light to reach deeper into a plant. Overgrown areas can trap fungal spores, along with the damp air and darkness fungi thrive on. Pests are also more likely to make themselves at home in tight spaces.
Removing thin growth, along with the four D’s mentioned earlier, will create a plant which is stronger and healthier overall. The airflow and sunlight in the spaces you create will reduce pest and fungal disease problems.
Pruning to eliminate narrow crotch angles will promote a stronger plant structure. Wide crotch angles are better able to withstand the weight of snow and ice, and they keep a plant sturdier in strong wind. What is a crotch angle? It’s the angle between where a new stem meets the branch or where a branch meets the trunk. The ideal angle for strength is a stem or branch that extends at a 45-60 degree angle from its source.
Bonsai is the ultimate technique of pruning to restrict growth. At some point, all plants will need pruning to keep them from outgrowing their allotted space.
Cutting back the plants we have worked so hard to encourage to grow can just seem so wrong. That can be particularly true when dealing with a stunted or unbalanced plant. Whether we like it or not, sometimes the best approach is to reach for the pruners.
If an area of one of your plants isn’t growing as vigorously as the rest, you might think the best way to even things out is to cut the larger areas back. That approach will balance things temporarily, but remember that cutting growth encourages new growth. Vigorous shoots will regrow just as – or more – vigorously after they’ve been cut.
Cutting the stunted area back a bit will stimulate the growth necessary to create structural balance over time – even though it might pain you to do it. I know that trimming the smaller area will cause it to grow, but sometimes, I still have to take a deep breath and force myself to make those cuts.
Just like an unruly child, unpruned plants can get out of control. They will overtake the garden space, crowd a pathway or swallow up a support. That’s when it’s time for what Steve calls remedial or renovation pruning. Don’t be afraid to show your plants who’s boss. After all, it’s your garden.
This is when pruning fear can really set in, but plants are very forgiving and usually very determined to survive. A healthy plant can be cut back nearly to the soil surface, and it will grow back. In fact, it will send up so many shoots that they can become a problem all their own.
Whenever possible, the best approach is to cut back no more than one-third of the plant overall. That is particularly true for trees. Sometimes, it’s necessary to take more drastic measures, but in either case, remember that significant cuts will result in significant re-growth. Steve recommends that you have a plan in mind for managing the new growth that comes.
As new shoots develop, the real pruning work begins. It’s important to observe the new growth and select which shoots should be allowed to mature and which should be pruned out. Don’t be afraid to apply tough love here. Many gardeners miss the important step of managing the new growth. That inadvertently creates a cycle of harsh pruning, followed by overgrowth which requires harsh pruning down the road.
Remedial pruning shouldn’t be a regular part of your gardening experience. Don’t be afraid to be aggressive with your pruning cuts. Just be sure to follow up to train and maintain the new growth which comes.
There’s one pruning method that might be considered remedial by some, but it’s really just a crime against nature.
Tree topping is a common practice in many regions throughout the U.S., and Steve laments that it happens in the U.K. as well. Unfortunately, there are still plenty of homeowners and landscaping companies who swear by tree topping as a safety measure, but it causes much more risk than it alleviates.
When the crown of a tree is cut off, the tree is starved of its energy-producing foliage. In response, the tree produces an abundance of shoots – known as water spouts. This isn’t healthy growth. It’s a desperate move by the tree to produce foliage quickly for energy. Water spouts are weak growth, and as they mature, they are extremely likely to break off and do damage.
I used to live in an area where tree topping was a regular practice. I saw so many beautiful, decades-old trees die within a few years of being topped. Not only was it tragic to see these majestic beauties fall victim to poor management, but it created greater hazards for the homeowner and, eventually, greater expense when the dead tree had to be removed.
Tree topping is never – ever – the right thing to do.
An often overlooked technique of pruning that Steve covers in his book is root pruning. Steve has heard this technique referred to as “bonsai for big boys.”
When a plant is out of control, pruning the growth can be effective, but sometimes, it can be better to force the tree to focus its energy on growth under the soil surface. When a plant’s root system is trimmed in the spring, it will divert more energy to root development than to foliage development. In other words, to recover below ground the plant slows things down above ground.
So, how do you trim the root system? Tie a string to a stick and use that to create a circular guideline around the drip line of the plant. The drip line is the widest point of the reach of the foliage. Following the circular guide, dig a trench about the width and depth of a spade, severing the plant’s feeder roots as you go along. Then, just backfill the trench with native soil.
Throughout the growing season, the plant will direct its energy to healing the root cuts and develop a more fibrous, robust root system. Root pruning can also prepare a plant for transplanting, creating a denser root ball which will be better able to recover after being moved.
Always More to Learn
There are other specialty techniques and pruning nuances to explore. Just like any aspect of gardening, there is always more to learn, but these basic principles and the wealth of information in Steve’s book provide all the guidance a gardener needs to let go of pruning phobia.
Don’t be afraid to experiment. Pruning is an important aspect to good gardening, and it shouldn’t put you into a cold sweat.
One good tip to bear in mind is that one of the best times to feed a plant is after a pruning session. After all, it’s the leaves that produce so much of the energy a plant needs to grow. So when you remove some of that energy-production, give the plant a little something back. Just don’t overdo it.
Remember that, in spite of everything that we or Mother Nature might throw at them, plants are predisposed to grow. Steve shared a fascinating example of that natural determination. If you’ve ever grown a fruit tree, you may have noticed some of the early fruit was aborted by the tree and dropped to the ground. That’s not a sign that the tree is unhealthy.
We love to eat the fruit, but its real purpose is to allow the tree to reproduce. Steve taught his horticulture students to gather some of the aborted fruit along with some of the fruit left on the tree. When cut open, the aborted fruit always contains fewer seeds than what had remained on the tree. A tree will devote its energy to the fruit containing a healthy seed count and which is most likely to be successful for reproduction.
I don’t know about you, but I never get tired of these examples of the wonder of the world around us.
If you haven’t already listened to this discussion, I strongly recommend you scroll to the top of the page and press the Play icon in the green bar under the page title. Not only did Steve and I share a lot of laughs, but he mentions a few other specialty techniques and tips on how to put a bad mood to work in your rose garden.
Links & Resources
joegardener Online Academy: Master Pests, Diseases, and Weeds – Just $47 for lifetime access! Watch for my new course on seed starting coming January 30, 2020!