Take note of the specific type of plant being pruned and ask yourself what the pruning goal is. Think about the desired effect before deciding what time of year and which pruning technique to implement. There are many reasons to prune:
- Direct growth
- Limit size
- Achieve artificial form
- Promote plant health
- Prevent/repair damage
- Maintain safety
- Alter or rejuvenate
- Remove undesirable growth
- Emphasize an attractive feature
- Push flower/fruit production
Basic Pruning Tools
Hand pruners (bypass/anvil): Good for cuts ¾ to 1 inch in diameter. Many professionals use Felco brand because of its high-quality materials, replaceable parts, and specialty styles including pruners for small hands or left-handed gardeners.
Loppers (bypass/anvil): Larger hand pruners with longer handles; can cut branches up to 2 or 3 inches in diameter depending on handle length and blade size. Long handles help reach higher into trees or deeper into dense shrubs.
Pruning Saw (folding): Powerful tool for cutting thicker/harder wood. Slightly bowed with sharp teeth on all sides, it quickly cuts while moving forward and backward. Lightweight plastic models and older wood styles available.
Terminal Bud: Grows at the tip of a shoot, making that shoot longer over time. While actively growing, terminal buds send hormones out to prohibit the growth of lower buds.
Lateral Buds: Grow along the sides of the shoot where leaves attach; produce sideways growth that results in a plant’s bushiness. Until the shoot grows long enough, lateral buds stay dormant under the influence of terminal bud’s hormones.
Lateral Pruning (Heading Back): Removing the terminal bud on a branch or stem to a lateral bud or shoot growing in the preferred direction. Heading stimulates growth of lateral buds just below the cut, resulting in clusters of shoots; helps to change the direction in which a plant sends out branches.
- Flat cut stimulates two new shoots to grow below the cut.
- Diagonal cut produces one shoot from high end of the cut.
Shearing: Cutting all branches to one desired length, creating an even surface, as in a hedge.
Thinning: Cutting a limb or branch back to where it begins (trunk) or to its junction with another branch; encourages growth on remaining parts of the plant and aids in circulation. When a plant sends up stems directly from the ground (suckers), the cut should occur at ground level.
Pinching: Removing new shoots with shears or forefinger and thumb; only attempt on soft, new growth. Often done on late-blooming perennials to delay budding and create a dense, bushy form (e.g. Chrysanthemums, Asters, upright Sedums).
Dead, Damaged, Diseased & Dysfunctional Growth (4 Ds): Scrape bark for signs of life. Remove dead/diseased parts immediately. Sterilize tools with disinfectant between each cut to prevent spreading of disease. Identify suckers and water sprouts as dysfunctional growth; learn how to manage. Deadwood removal does not count against pruning budget.
Timing: To Prune or Not to Prune
Most plants have a “pruning budget” and can afford to only lose 25–30% of their growth at one time. It is important to continuously “balance your budget” by evaluating how much of the plant has been removed. When pruning, remember to stand back and assess the process on a regular basis. I like to take a photo before I begin and again once finished. Also, remember—blooming time influences pruning time.
Shrubs that flower on previous year’s wood should be pruned after blooming (usually late winter or early spring bloomers): Camellia, Ceanothus (California Lilac), Chaenomeles (Flowering Quince), Deutzia, Forsythia, Hamamelis (Witch Hazel), Hydrangea macrophylla and quercifolia, Kalmia (Mountain Laurel), Kerria, Kolkwitzia (Beauty Bush), Philadelphus (Mock Orange), Pieris, Rhododendron/Azalea, Spiraea (bridal wreath types), Syringa (Lilac), Weigela
Shrubs that flower late in the growing season on current season’s shoots should be pruned before spring growth occurs: Buddleia (Butterfly Bush), Callicarpa (Beautyberry), Caryopteris (Bluebeard), Clethra, Hibiscus syriacus (Rose of Sharon), Hydrangea arborescens and paniculata, Lagerstroemia (Crepe Myrtle), Roses (repeat bloomers), Spiraea (Shrubby types), Vitex (Chaste Tree). Exceptions to the rule: Clematis, Spiraea, and Hydrangea pruning usually depends on the variety/bloom times.
Winter pruning of deciduous trees/shrubs will make them grow more vigorously in the spring; summer pruning will make them grow slower the following spring. Winter pruning is recommended for young deciduous trees/shrubs and fruit trees to encourage them to grow more vigorously while training for shape.
Summer pruning is recommended for full-sized or overgrown plants to slow their growth. Plants that haven’t been pruned recently should be partly pruned in the summer and partly in winter to avoid over-pruning. Removing too much in the summer will stunt the growth; pruning off too much in late winter will cause lots of suckers and water sprouts.
Late spring pruning doesn’t affect growth, so it’s a good time to tend to neglected plants. It’s also a good time to prune fruit trees since it is obvious which branches are fruit-producing and a good time to remove suckers/water sprouts by breaking them off while they are still soft and pliable.
Never cut-back to bare wood: Camellia, Heather, Juniper, Lavender
Shrubs that tolerate severe pruning (removal of more than standard pruning budget): These shrubs can be rejuvenated by cutting the whole plant low to the ground—they will send up vigorous new growth from the base and often also into the surrounding root area: Abelia x grandiflora, Berberis (Barberry), Buddleia (Butterfly Bush), Callicarpa (Beautyberry), Chaenomeles (Flowering Quince), Cornus s. (Twig Dogwood), Fatsia japonica (Japanese aralia), Forsythia, Hibiscus syriacus (Rose of Sharon), Hydrangea, Kolkwitzia (Beauty Bush), Ligustrum (Privet), Mahonia (Oregon Grape), Perovskia (Russian Sage), Philadelphus (Mock Orange), Rhododendron/Azaleas, Roses, Salix (Willow), Sarcococca (Sweet Box), Spiraea
For forcing indoors: Prune in late winter as tiny buds begin to swell; once brought indoors, leaves/flowers emerge early in a surprise surge of growth: Maples, Birch, Redbud, Quince, Dogwood, Forsythia, Witch Hazel, deciduous Magnolia, Malus (apples, crabapples), Prunus (cherry, peach, plum), Salix (willow), Lilac—crush stems before putting in water.
Seasonal Guide for Common Trees & Shrubs
January to March:
- Young or weak trees and shrubs
- Summer blooming shrubs (e.g. roses)
- Damaged branches from winter
- Blueberries at least 3 years old
March to mid-April:
- Non-blooming broadleaf evergreens
- Evergreen/deciduous hedge plants
- Trim winter dormant grasses
- Check for new growth buds on hardy fuchsia—prune back to green shoots when they appear
April to May:
- Shear back broad-leafed and needled evergreens
- After bloom, prune spring-flowering trees and shrubs (e.g. azaleas, camellias, daphne, forsythia, lilac, rhodies, cherries, plums, deciduous magnolias, crabapples)
June to August:
- Shear back broad-leafed and needled evergreens
- Trim overgrown or neglected deciduous trees and shrubs
- Remove suckers, water sprouts, and spent blooms on flowering plants (wait until hydrangeas are done blooming)
- Late-summer pruning of Japanese maples can help shape/train, but may be easier if done in late winter while leafless
- Avoid pruning Japanese maples in early spring (sap flowing)
September to mid-December:
- Winter preparation (for safety; branches vulnerable to breakage/damage)
Late December to mid-February:
- Perennials/shrubs that die back over winter
- Fruit trees in dormancy and blueberries
- Deciduous non-blooming trees
- Many summer-blooming clematis
Steps for Successful Tree Pruning
Always respect individual plant’s pruning budgets.
- Remove all dead or diseased wood (anytime).
- Remove or cut back limbs that come out of the trunk at a narrow angle.
- Remove a limb that comes out of the trunk a few inches directly above or below another branch.
- Thin out water sprouts; if you remove all during winter, you will get many more back (best time is June to August). On the top of the tree where the limbs are exposed to the sun, leave one every few feet, but remove about ¼ of its height
- Remove dangling branches or cut them back to an outward growing branch/bud.
- Remove crossing or crowded growth.
A Commonly Asked Question: “How Do I Prune My Hydrangeas?”
It’s easy, really! First, some definitions… There are three ways in which hydrangeas flower—those that bloom on new wood, those that flower on old wood, and now there are some newer selections that flower on new and old wood and therefore require little or no pruning each year. Old wood refers to branches that have been on the hydrangea since the summer before the current season. New wood refers to the branches that will develop on the plant during the current growing season.
Method 1 is for hydrangea types that bloom on old wood (last year’s branches). Prune these hydrangeas only in the summer before late August, before they set their bloom buds for the next year. This group of hydrangeas produces flower buds around late August, September, or October for the following summer’s blooms. If those stems are removed (pruned) in the fall, winter, or spring, the bloom buds will be removed and there may be little or no bloom the following summer. Examples: Hydrangea macrophylla ‘Nikko Blue’ or ‘Glowing Embers’, Hydrangea quercifolia
Method 2 is for hydrangeas that flower on new wood (new branches). Prune these plants in late summer after they have bloomed. They cannot be pruned in the spring when they are preparing to flower because you will cut off the buds. Examples: Hydrangea arborescens ‘Annabelle’, Hydrangea paniculata
Method 3 is for hydrangeas that flower on both new and old wood. Prune these hydrangeas only if they are getting too large for the space or if you want to remove old flowers. The best time to prune them is after they flower in late summer. If you prune them much beyond late August, you will risk removing the flower buds that are developing on the current branches. Examples: Hydrangea macrophylla ‘Endless Summer’, ‘L.A. Dreamin’
Basic Perennial Division Times
Generally, perennials should be divided during the season opposite in which they flower. So, spring and early summer bloomers should be split in fall, and late summer to fall bloomers in early spring. The idea behind this is that the new plants will be able to put all of their energy into root and leaf production rather than flowering, and therefore have an easier time becoming established. Ideally, newly divided plants should have 4–6 weeks to grow before hard frosts and winter sets in.