Pruning Fundamentals
> Before you start pruning
> Understand new wood & old wood
> When to prune
> Make a pruning plan
> What to prune and remove
> How much to remove
BEFORE YOU START PRUNING:
#1. Ask this most important question
Before you start pruning, ask yourself: “Are the flowers or fruit on this plant important to me?”
If the answer is NO:
There are many plants grown for the beauty of their leaves, bark and structure. When flowers and fruit are not important, it won't matter that a gardener removes the wood from which the flower and fruiting buds emerge. Pruning may eliminate such wood in favor of accenting other features or traits of the plant. If you answered "no", skip ahead to When to Prune.
If the answer is YES:
Then it is ESSENTIAL to identify the wood from which flowering and fruiting buds emerge and to preserve as much of that wood as possible during the pruning process.
#2. Know if your plant blooms on NEW WOOD or OLD WOOD
Depending upon the plant, flowering buds may form on old wood, or new wood or both. If you are not aware of this distinction, pruning may remove the precise wood that you intended to keep!
NEW WOOD is wood that will emerge during THIS year's growing season.
OLD WOOD is the wood that emerged during LAST year’s growing season. It is often distinguishable from older wood by its lighter color. Alternatively, it is possible to follow a branch down from its tip to find the scar that marks the point from which last year’s growth emerged.
Determine whether a plant flowers on old wood or new wood - check online or consult the pruning lists for Flowering trees & shrubs, fruit trees, or native plants, and then address when and what to prune.
WHEN TO PRUNE
Some plants emerge from dormancy in the spring and grow until the next winter, while others emerge from dormancy in the winter and grow until the summer heat sends them into dormancy (e.g., many native plants).
| Understand GROWING & DORMANT seasons “Growing season” • the period when a plant is actively growing, producing flowers and fruit • does not necessarily coincide with spring or summer “Dormant season” • refers to the period when the plant is not actively growing • does not necessarily mean winter |
Plants that bloom on NEW WOOD:
Plants that bloom on OLD WOOD:
Plants that bloom on NEW & OLD WOOD
TWO TIMES TO AVOID PRUNING:
1. When leaves are dropping or growing
Do not prune a plant while its leaves are growing (“leafing out”) or dropping. Leafing out is energy intensive. Pruning at this time requires plants to devote energy to sealing pruning wounds, which can severely slow desired growth. Dropping leaves coincides with the movement of plant energy (sugar) down the limbs and into the roots. Removing branches at this time removes sugars that have not yet moved to the root system.
2. Don't make major cuts during a plant's growing season
Do not undertake major structural pruning of a plant (i.e., large diameter cuts) outside its dormant season except to remove dead wood. Such cuts could materially weaken the plant, send it into shock or cause it to “weep” sap in a manner that can be unsightly and/or unhealthy.
MAKE A PRUNING PLAN
Step 1: ASSESS
Is the plant healthy?
Check to see if the plant is healthy. If not, do not prune it. Restore it to health first. Signs of an unhealthy plant:
• lesions that are weeping sap from the trunk or multiple branches
• significant branch die-off
• blackened bark that may indicate a serious disease (e.g., fire blight)
• early leaf drop on the side facing the sun which could indicate insufficient irrigation or too much sun
• early leaf deformity and leaf drop which could indicate a foliar or vascular disease.
Consider a plant's structure and relation to landscape
Walking around the plant, see its structure, step back to see how it fits into the landscape and make a plan to achieve one or more of the objectives in “What Is Pruning". Every cut should serve that plan.
Do some comparative research
Go online to see how others have shaped the same plant. Make a list of the attributes that make the plant attractive and prune to accent them. But accept that two or more identical plants in the same garden may not grow in identical ways. Each may need to be pruned differently.
Consider your goals
Many professional pruners assess before they begin:
• What are the unique characteristics of this particular plant?
• What is it trying to be?
• Should pruning try to alter those characteristics or accept and incorporate them?
Step 2. FOLLOW THE BASIC GUIDELINES:
Three D’s, Three C’s, and Three S’s
The following guidelines provide a road map for a basic pruning plan.
WHAT TO PRUNE & REMOVE
Plants that grow from CANES:
Cane plants grow in the form of shoots or branches that emerge directly from the root stock.
Examples: buddleia (Butterfly Bush), blackberries.
• Some cane plants can be completely pruned down to their root stocks (coppiced) and will generate healthy new growth in the spring.
• As a less drastic alternative, all cane plants can be pruned by removing some older entire canes each year to make room for new canes – allowing the plant to continually refresh itself.
• If the goal is to completely rejuvenate an old plant, remove one-third of the canes each year for three years.
Plants that BRANCH:
Plants that branch generally require cuts that:
• increase the sunlight exposure into the plant
• increase air airflow into and across the plant.
Most plants grow more vigorously on the side that faces the sun.
As a result, the growth on the sunny/strong side often is denser than the growth on the shady/weak side. This dense growth on the strong side not only creates an imbalanced shape, but also blocks sunlight from passing through the plant to the weak side.
• On the sunny/strong side, remove dense vegetation that blocks light and air
• On the shady/weaker side, remove only what is necessary to shape and rebalance the plant.
All flowering and fruiting plants require sunlight and air deep within the interior.
• Prune to allow light and air to penetrate from above, not just across, a plant.
• Step back or stand on a ladder to see if the upper branches are blocking sunlight and air from penetrating down into the plant.
WATER SPROUTS and SUCKERS
Water sprouts are branches that grow vertically or nearly vertically from lateral branches. With rare exception, they should be removed:
• These sap the strength of the plant
• They are weakly attached to their host branches, making them generally poor choices for scaffold branches in future years. Scaffold branches are the main branches of a tree.
Suckers are branches that grow directly from the roots themselves. They also should be removed.
• If they are small, they may be torn from the roots by hand to remove the bud structure from which they emerge.
• As explained in the section on Fruit Trees, suckers that grow on the trunk of a grafted plant below the point of the graft also should be removed.
HOW MUCH TO REMOVE
• Follow the 1/3 rule. As a rule of thumb, at each pruning, remove no more than one-third of a shrub or tree.
• Over-pruning = risk of shock or overreaction. Removing more risks sending the plant into shock or promoting overly vigorous growth at the site of the cut, which defeats the purpose of pruning.
• Do less if plant is compromised
Removing less may be required if the plant is old or diseased and, therefore, less vigorous.
• Go slowly and gradually. If the goal is to reshape a plant, implement a plan over two or three years.
• Note: Pruning is plant-dependent. Specific plants may not tolerate removing as much as one-third and some may tolerate removing more.
Know if your plant will BACK BUD
In addition to visible buds, many plants have dormant buds on bare branches below their leafy ends, or on the trunk. Pruning the leafy portions of branches can activate back buds below each cut. Some plants contain widely dispersed back buds and some contain few. To determine, look into the plant’s interior – at its trunk and branches – to see if they are sending out new shoots along bare wood.
Caution: Not all plants will back bud. Pruning plants that do not back bud at all or unreliably may leave large gaps or openings in the plant structure that will never fill with new branches. Check before proceeding!
OTHER CONSIDERATIONS
Clean up after pruning
This step is frequently overlooked, but it is critical.
• Often, trees and shrubs are planted too deeply - their root crowns, which should reveal a slight flare, are buried in excess soil, leaf debris or mulch. (The root crown is the place where the main trunk and the roots join at the soil line.)
• Clear debris away from the start of the flare to avoid root and other diseases caused by excess moisture on the crown.
• For shrubs, remove all leaves that have settled within the plant at its base. These too are breeding grounds for plant diseases.
ADDITIONAL RESOURCES
The following provides helpful additional information on when and what to prune with respect to flowering trees and shrubs.
How to Train Young Trees: Structural Pruning for Home Gardeners (UC Davis, 2012): https://www.youtube.com/playlist?list=PL56F9A1198F063463.