When Not To Prune (2024)

An old boss of mine used to say that “the best time to prune is when the knife is sharp.” His logic was, basically, prune when you have the time. Technically, there are more advantageous times to prune, but really, who has the time and energy to make a spreadsheet of all the plants in the yard and document the short window of time they ideally should be trimmed? That’s not realistic or necessary. In most cases, you won’t kill, ruin, or maim a shrub if you prune it outside of its preferred pruning window. Instead of focusing on exactly when, say, a smokebush (Cotinus spp. and cvs., USDA Hardiness Zones 4–9) prefers to be cut, I prune it whenever my knife is sharp—as long as I abide by a few golden rules of when not to prune.

When the sap is flowing

Sap is the lifeblood of a plant, so if you make a cut when it’s coursing through the stem of a tree or shrub (early spring for many plants), you’re essentially opening a wound. This wound can keep bleeding, sucking the life out of a branch or even the entire plant. The incessant flow of sap also acts like a beacon, attracting all sorts of potential problems. The sweet nectar is often irresistible to many animals, including bears and birds. The need to satisfy their sweet tooth sometimes causes indiscriminate destruction to a tree. Insects may also be summoned to feed, and they can carry pathogens that introduce diseases to plants. When sap starts to dry, it has a tendency to mold, which may also open the door to diseases. Make a small test cut to find out if the sap is still flowing before committing to a full pruning.

Heavy-bleeding plants

Birches (Betula spp. and cvs., Zones 2–9)
Cherries and plums (Prunus spp. and cvs., Zones 3–9)
Smokebushes (Cotinus spp. and cvs., Zones 4–9)
Filberts (Corylus spp. and cvs., Zones 3–9)
Hop hornbeams (Ostrya spp. and cvs., Zones 5–9)
Hornbeams (Carpinus spp. and cvs., Zones 3–9)
Maples (Acer spp. and cvs., Zones 3–9)
Silverbells (Halesia spp. and cvs., Zones 5–9)
Snowbells (Styrax spp. and cvs., Zones 6–9)

During excessively cold temperatures

Plants are more brittle in cold temperatures. Messing around with them may cause branches to snap and split unintentionally. It’s minor, but it could impact the look of a plant or create a haven for insects and diseases later. Don’t prune when the temperature falls below 25°F. Stay by the fire and enjoy its warmth instead of heading outside to the garden.

Excessively at time of planting or transplanting

If sap is the blood of the plant, then the branches and roots are the muscle and fat. All the energy (in the form of starch or sugar) is stored here. When you first plant or transplant a tree or shrub, it inevitably loses some root mass, and some folks think they should compensate by removing some of the plant’s overall mass. But a plant at planting time becomes stressed and uses lots of energy to try to reestablish itself in its new home. Pruning at this time can remove vital energy for the road ahead. Remove too much of the plant, and the energy glut can cause the plant to starve and possibly die. Wait until your new plants go into dormancy to prune.

During hot, dry weather

In winter when limbs are large

This principle always gets me in trouble. Many arborists prune in the winter. It’s the best time to see the shape of a tree. When making a large cut, though, the cambium layer (through which water and nutrients flow) on many trees can desiccate, meaning it will take longer for those wounds to heal. This can cause unsightly wounds and can possibly invite diseases and insects if not done properly. I find it is best not to “limb up” a plant in winter. Limbing up is the process of exposing a trunk for several reasons: to better see pretty bark, increase sight lines, or for practical reasons. Wait until early or late summer instead, when the trunk on a maturing plant is getting fatter because it’s storing its food. This heals the wound more quickly, making for a scar-free trunk.

Just prior to flowering

If I had a nickel for every time I heard, “Honey, why aren’t our (fill in the blank) flowering?” Obviously, if you prune before flowering, you cut off the flower buds. This is not a detriment to your plants but can be one to your ears. The best practice is generally to prune right after flowering.

Tip: Always consider safety first. Wear protective gear—safety glasses or goggles are a must. Gloves are a good idea as well. And consider calling a licensed arborist for any pruning task that prevents you from standing on terra firma.

Throughout winter, if plants have a pithy center

Some Tools Are Better Than Others

When it comes to pruning tools, there’s a plethora to choose from, in every imaginable shape and size. Not every item in the shed, though, is suited for pruning. It’s important to use the right tool for the job. The following tools are my favorites because they are ergonomic, require less maintenance, last longer, and are easy to use.

1. Bleach and rubbing alcohol

Diseases can be transferred from one plant to another—even one branch to another. Use a 5% bleach-to-water mix to regularly disinfect your tools. Additionally, rubbing alcohol is best for cleaning pitch and gum off tools.

2. Lopping shears

When pruning larger branches, use a saw, which makes a cleaner cut. Loppers bruise plants badly. They are good only when used to coppice or to demolish a plant before removing it completely.

3. Pruning saw

A saw should be used when a branch is too big for a hand pruner. Remember to make slow, steady strokes for a clean cut. I prefer brands with interchangeable blades so when one inevitably breaks, I don’t need to buy a new saw.

4. Pocket multitool

These babies have everything in one place: tools for fixing mechanical issues on my pruners, blades for deadheading, a two-sided file for sharpening, scissors for cutting twine, and a small saw for making minor cuts.

5. Pole pruner

This is for pruning small branches that are above your head—while you’re standing on the ground. I prefer brands that offer the cut-and-hold option so I can control where the branch falls (i.e., not on my wife’s perennials).

6. Hand pruner

This is the tool you’ll use the most. Make sure the branch fits between the blades; if it doesn’t fit, use a pruning saw. Okatsune is my go-to pruning brand because their pruners stay sharp longer and make the cleanest cuts I’ve ever seen.

Ed Gregan is a nurseryman with Carlton Plants in Dayton, Oregon, and has more than 35 years of experience pruning (and not pruning) every plant imaginable.

Photos: Danielle Sherry; Michelle Gervais; Ann E. Stratton, Brittany Carlson, Steve Aitken, Friedrich Strauss/gapphotos.com; Amanda Darcy/gapphotos.com; Melissa Lucas, Jennifer Benner

FAQs

When Not To Prune? ›

Plants are more brittle in cold temperatures. Messing around with them may cause branches to snap and split unintentionally. It's minor, but it could impact the look of a plant or create a haven for insects and diseases later. Don't prune when the temperature falls below 25°F.

Learn More Now ›

Is there a wrong time to prune? ›

Pruning at the wrong time of year

Most plants are pruned in winter, when dormant, but there are exceptions. Cherry and plum trees, for example, are susceptible to silver leaf disease, and should therefore be pruned in summer when the risk of infection is reduced.

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When to avoid pruning? ›

Avoid pruning in fall.

Trees and shrubs reduce their energy production as the growing season ends, so new growth in autumn will use a plant's stored energy reserves. Dieback from a freeze means that energy used for this growth was wasted.

Discover More ›

What month is best for pruning? ›

February is the best time to prune your trees – never prune in April, May or June.

Trimming off dying or diseased branches protects your trees from further harm.
You can prune to promote new tree growth or suppress unwanted growth.
Pruning can keep branches from becoming too large and hazardous.

Jan 31, 2021

What is the 1 3 rule for pruning? ›

2. Follow the 1/3 rule. Many people are intimidated when they try to think about how much they can prune without damaging the shrub's health and vigor. When making pruning decisions, keep in mind that you can safely remove up to one-third of the plant's growth at any one time.

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Why shouldn't you prune in summer? ›

During hot, dry weather

Much like us, plants get stressed when they are dehydrated. Robbing them of their reserves of moisture by pruning away foliage can cause death. Instead of reaching for the shears, spend your time moving the sprinkler onto your plants.

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What is bad pruning? ›

An improper cut like a flush cut (cutting too close to the trunk) or a stub cut (cutting too far from the trunk) can cause irreversible damage to a tree. A flush cut removes the branch collar and leaves a large wound in the side of the tree that won't heal properly.

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What is the May rule for pruning? ›

The “May Rule” has helped me deal with that worry. It advises that most plants that bloom in or after May should be pruned in February and early March while those that bloom before May should be pruned only after their flowers fade. Of course, for every rule there is an exception.

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How late in the year can you prune? ›

Preventative pruning, and major pruning, should be done early in the spring, while the plant is dormant. Minor pruning, shaping, and trimming can be done all summer as needed. Don't prune plants too heavily in the fall, when plants are getting ready for winter.

Keep Reading ›

What is the first rule in pruning? ›

ALWAYS prune back to or just above a growing point (branch or bud) or to the soil line. NEVER leave a stem or branch stub. NEVER top a tree to “rejuvenate” growth. Â This ruins the plant's natural shape and greatly increases its susceptibility to diseases, insect pests, and storm damage.

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What is over pruning? ›

Over-pruning, sometimes done as a topping or lion tailing, involves removing an excessive amount of a tree's canopy. The result often leaves stubs or reduces the tree to an unnaturally small size that goes against its genetic growth pattern.

Should you trim low branches on trees? ›

Young trees need their low temporary branches to provide sustenance, though they should be kept short enough not to compete with permanent branches. Low temporary branches also protect the trunk. As the tree grows taller, the lower branches may be removed, keeping desirable branches.

Read On ›

When should you not trim bushes? ›

Do not prune deciduous shrubs in late summer. Pruning shrubs in August or early September may encourage a late flush of growth. This new growth may not harden sufficiently before the arrival of cold weather and be susceptible to winter injury.

Is June too late to prune? ›

Prune shrubs that flower before mid-June after they flower. For these spring-blooming beauties, remove the largest stems, cutting them back to the ground. This causes the plant to push out new growth from both the crown and all remaining stems. Prune any other stems to shorten or shape the shrub.

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Can I prune trees in summer? ›

Summer pruning removes leaves (food manufacture), will slow fruit ripening, and exposes fruit to sunburn. Summer pruning can be beneficial, however, when used to slow down overly vigorous trees or trees that are too large. It is usually done just after harvest.

Is there a wrong way to prune? ›

A proper pruning cut minimizes the damage done to the tree and allows it to heal quickly. An improper cut like a flush cut (cutting too close to the trunk) or a stub cut (cutting too far from the trunk) can cause irreversible damage to a tree.

View Details ›

What happens if you prune too late? ›

In areas with cold winters, avoid pruning after the middle of August. If you prune too late, you may stimulate new growth that would not have time to grow thick, protective bark before the killing frosts of winter.

Is it okay to prune now? ›

As a general rule, a light summer pruning can be performed on most deciduous trees and shrubs. Heavier pruning should be performed when the tree is dormant, preferably in late winter before active growth begins.

How do you fix pruning mistakes? ›

If you make serious seasonal pruning mistakes and prune a tree in summer or fall, you may have removed buds, flowers, or fruit. The solution is to wait until winter and prune again using thinning cuts or reduction cuts.

Learn More ›

When Not To Prune (2024)

When the sap is flowing

During excessively cold temperatures

Excessively at time of planting or transplanting

During hot, dry weather

In winter when limbs are large

Just prior to flowering

Throughout winter, if plants have a pithy center

Some Tools Are Better Than Others

1. Bleach and rubbing alcohol

2. Lopping shears

3. Pruning saw

4. Pocket multitool

5. Pole pruner

6. Hand pruner

FAQs

When Not To Prune? ›

What is over pruning? ›

References