Canopy Thinning: Tips For Thinning Canopies In Trees

Canopy Thinning: Tips For Thinning Canopies In Trees

By: Bonnie L. Grant, Certified Urban Agriculturist

The beauty of a healthy tree can’t be understated. They add dappled shade to the garden, provide wildlife habitat, and create natural barriers against nosy neighbors. However, the lovely little tree you planted years ago can grow to become a monster, shading out all other life below and creating a moonscape of scraggly, leggy plants and patchy sod. In order to increase the tree’s health and for the well-being of lower story plants, it is useful to thin the canopy occasionally to let in light and air. You don’t need to be an arborist to know how to thin out a tree’s canopy but a few tips can be useful.

Thinning Canopies in Trees

The reasons for thinning tree canopies go beyond increasing light and air. The practice is also useful to keep a tree in a certain growth habit, prevent it from getting too tall, or keep limbs from getting invasive. Whatever the motivation, canopy thinning is a selective pruning practice that should be done when the plant is dormant for best results.

The goal with tree thinning is to reduce the number and thickness of the tree branches in the crown. Crown thinning trees allows more light to come into the core of the branches to enhance the growth of leaves and stems. It also allows more air to circulate, which reduces fungal and pest problems.

Additionally, thinning tree canopies reduce the weight to stabilize and strengthen the plant. Heavy thinning should be discouraged, as it can encourage the formation of unwanted growth, such as water spouts, but light thinning will encourage new needle or leaf growth, which provides increased photosynthesis and health.

Crown Thinning to Brighten Shade Gardens

The light pruning required to open up the canopy and bring in a bit more light is mostly done on the outside of the tree. This is where heavy growth has caused limbs to branch out and shade lower story plants. Only the tips of the outer growth are taken back with proper canopy thinning.

Excessive interior limb removal makes the plant unstable and weak. The only interior material you need to remove are water spouts and dead or broken limbs and stems. Thinning should keep the plant in as natural a form as possible and focus on making a balance of branches for a sturdy scaffold.

The general rule is to remove no more than 15-20% of the foliage on mature trees to prevent spouts and weak growth.

How to Thin Out a Tree’s Canopy

Thinning removes branches that are 2 inches (5 cm.) thick. The thicker branches should only be removed if they are diseased or dead, as they form the scaffold of the plant and give it strength. Cuts should be at a slight angle to deflect moisture away from the cut surface and must be just outside the parent wood. Never cut into the main leader or trunk, as this can invite disease and rot.

The best time to prune is before the plant has begun new growth for the season and is dormant. Remove growth around the edges of the canopy for a tighter, more compact shape and then remove any broken and dead stems from the interior. Take care not to remove too much interior material as this produces a “lion’s tale” shape which is undesirable and weakens the tree.

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Read more about General Tree Care


Thinning an Oak Tree

Oak trees offer majestic splendor to the landscape and spectacular shade to your yard. Plus, they provide acorns annually, a treat for critters around your property. There are many varieties of oak trees, but most are fast growers, averaging a development rate of about one foot per year. A mature oak tree can reach 80-150 feet in height and spread over nine feet wide. With that kind of growth, large branches develop.

In heavy winds or under the weight of snow, those branches can break off the tree, potentially delivering a devastating impact to anything below. For this reason, it’s important to keep dead wood and unhealthy branches thinned. General pruning also facilitates healthy growth and handsome structure.

Step 1 - Choose Your Timing

Thinning any deciduous tree is best done in winter, when the sap is at the roots. Thinning of oak trees can also be done in midsummer after a growth spurt, once all the new leaves are producing food. It's not a great idea to prune in the spring or fall. Remember that removing a branch leaves a wound that must heal, so you don’t want to prune when the tree is putting its energy into actively growing.

Step 2 - Follow Safety Protocol

Oak trees create heavy branches, and you may be working high in the air, so use safety protocols as you work—wear safety glasses, a hard hat, and good quality leather gloves for protection. Use a ladder or climbing harness and try to remain level to the branch you’re working on rather than below it. When managing branches high up or small branches at a lower level, use a handsaw or pruning saw rather than a chainsaw.

Step 3 - Know the Proper Reasons to Thin Oak Trees

Most oak trees will grow and thrive with very little maintenance. In fact, cutting branches when not necessary will cause more harm than good so it’s important to create a plan that will meet your needs and benefit the tree. Oak tree foliage is thinned out to prevent obstruction of electrical wires, to allow light penetration into gardens and lawns, and to redirect the tree's growth vertically.

Focus on dead, diseased, or weak branches that can infect other parts of the tree. Also remove branches growing up into the center canopy of the tree—you want the center to remain open for proper airflow. In addition, cut branches that overlap each other, block driveways, threaten buildings, or are growing in a downward direction.

Step 4 - Thin the Crown

Look for branches in the crown that are causing crowding. Crown thinning maintains the natural direction of branch and limb growth, permits sunlight to pass, reduces wind resistance, and slows the oak tree's growth rate.

Step 5 - Thin the Bottom

Crown lifting removes the branches nearest the ground to ensure minimum ground clearance for pedestrians and tall vehicles such as buses, RVs, and freight trailers.

Step 6 - Make Proper Cuts

Don’t cut flush with the trunk. Instead cut outside the bark of the trunk so the existing bark can naturally grow over the wound left from the branch removal. This means you will leave about an inch of the branch attached to the tree.

Remove small branches early on when they are less than two inches in diameter. For larger branches, remove no more than ⅓ of a living branch. Cutting large branches back too harshly can stress the entire tree and cause it to die.

For longer branches, cut off in sections. If you attempt to cut the branch all at once, the weight of the branch can cause a tear rather than a clean cut, damaging the trunk of the tree. To properly remove a branch, make a cut on the underside of the branch about ¼ of the thickness, a few feet from the trunk of the tree. Then move to the top of the same branch to complete the cut. Removing the majority of the branch in this way takes the weight off and allows you to make a final, clean cut closer to the trunk.

Warning: If your tree branches are near power lines, call the electric company to handle the task to avoid the risk of electrocution. Also, if you are removing a large branch, use a rope to lower it once it is cut from the tree.


2. Ideal Trimming Times Depend on Species

No ideal time exists to prune or trim all species of trees. The best time to prune a specific tree depends on its age, health, growth pattern, and growing conditions. More importantly, the species of tree dictates the optimum trimming and pruning schedule.

Some flowering trees shouldn't be trimmed until their spring blooms have died. That's because the trees' blooms occur on last year's growth. If your flowering tree produces blooms on new spring growth, you can schedule trimming or pruning of those species of flowering trees in late winter or any time of year.

When you want to limit the growth of trees, schedule trimming of foliage trees after they have their initial growth flush in spring. Since the trees expend a lot of resources pushing their initial growth bursts, the trees are stressed right after their first growth flushes. Only trim trees after initial foliage flushes when you want to limit the sizes of the trees, since trimming at that time adds more stress to trees.

Palm trees generally require no pruning except to remove coconuts and large palm seeds throughout the hurricane season. Some deciduous trees are best pruned when dormant. Trees that are sick, diseased, or growing in unhealthy ways may be trimmed or pruned at any time of year.


Five Common Tree Pruning & Trimming Mistakes

We know it can be tempting to take care of much needed tree pruning on your own. Often, we just hire the guy down the street that's "handy with a chainsaw". Who doesn't want to save some money? Problem is, poor "cheap" pruning can permanently ruin the look of your valuable trees and often leave them susceptible to storm damage, disease and ultimately decline and death. Here are five of our top common pruning and trimming mistakes we see on trees around the DFW area.

  • Topping: This is usually one of the most obvious and ugly of tree pruning mistakes. It happens a lot with crapemyrtles (known as "crape murder") and other trees that were too large for the place they were planted. With crapemyrtles, it's also done because people think it will get them more blooms (it won't). Topping involves cutting away a large section of the top of a tree's crown, or all the leafing branches across the top half of the tree. What you're left with is a very ugly deformed specimen with severely weakend branch structure.
  • Bad Timing: There are good times to prune and bad times to prune it depends on the species and condition of the tree. In Texas, for example, oak trees should not be pruned from February through June, due to the spread of oak wilt disease. If a tree is already stressed, it should not be heavily pruned. You should always have your trees inspected by a certified arborist before you let anyone take a chainsaw to it, unless you're willing to lose the tree completely. Pruning west-facing branches isn't a good idea in the heat of the summer when you remove large limbs that shade the tree from the hot western sun, you can cause sun scald on red oaks, maples and other susceptible species. Sun scald results in wounds and damage to the trunk bark that can severely damage your tree.

  • Improper Cuts: A very common tree trimming mistake when removing branches is to cut them off too close, or flush, to the main trunk. By doing this, you remove the branch collar an area of tissue with specialized cells that help heal the wound. You'll recognize it as a small swelling, or bump, right where the branch meets the trunk. The callous that the branch collar cells creates will prevent disease from entering the trunk. When you cut that branch off flush to the trunk, you're opening a wound that can allow in disease and pests, putting your tree on a path to an early demise. Bark tears can occur when the proper steps are not taken when removing large branches. If you make the wrong cut in the wrong order, you can end up with a large branch falling and tearing or splitting your main trunk.
  • Over Pruning: No more than about 15% to 20% of a mature tree's foliage should ever be trimmed off at one time. In fact, 5%-10% is usually adequate. When you remove too much of the canopy, you'll leave the tree unable to produce enough food, transfer nutrients and structurally support itself. People often over trim and thin their trees in hopes of getting the grass beneath to grow properly (which rarely happens). If you have multiple trees in an area where you'd rather grow turn, often a better practice is to remove selected trees to let in more light, and perform structural pruning on the remaining trees so that you can have both healthy trees and turf.

Raising the Canopy Too High: Otherwise known as Lion's tailing, or as we like to call them "Broccoli Trees". Again, unskilled labor often removes far too many large lower branches in an effort to raise the canopy and grow more turf grass. What you end up with is a very tall bare trunk with a small amount of foliage canopy left at the top. It looks like a lion's tail, or stalk of broccoli. You can read more about this pruning mistake and the problems it causes HERE.

Entry Info

Categories: Trees, Pruning, Disease
Tags: Disease, Preservation, Pruning, Trees
Posted: August 19, 2013


Amelanchier – the tree to replace net curtains

You may want trees for privacy from the street, especially at bedroom height. Or you may just prefer to wake up in the morning looking at leaves rather than streetlamps and houses.

Amelanchier is deciduous and loses its leaves in winter – but, on the other hand, you probably keep your curtains closed for longer in winter.

Amelanchier has a ‘vase’ shape and its glorious colour makes it a good privacy tree. You also have plenty of space (and enough light) at ground level to plant other things.

Posy Gentles has replaced a conifer in her front garden with a vase-shaped amelanchier. It has beautiful blossom in spring and gorgeous autumn colour. It’ll probably take two years before it screens the living room window completely.

My neighbour’s amelanchier offers light-dappled privacy and turns the colour of the house’s brickwork in autumn. It has, however, taken 12 years to get to around 30ft from a small tree.


Pruning Tips and Techniques

Pruning hints for California native plants

So, it’s been 5-10 years since you filled up your garden space with a buying spree at your local Native Plant Society Sale. Somehow all those little gallon-sized plants looked rather lonely when you first set them out. Now they have all grown bigger than you could have imagined. It’s time either to remove some (perish the thought!), or to play referee with the pruning tools.

What you need are good muscles, sharp clean tools and most importantly, a clear idea of what you want to achieve to attain a vegetative truce in the garden for a year or two.

Pruning. Credit Allison Levin

Your garden vision with proper timing and techniques

  • Do you want a hedge? Decide whether tightly or informally shaped is right for your plant and space, then use shears or hand pruners, respectively. Make the tops of hedges narrower than the bases or the top growth will shade out the bottom leaving bare twigs and branches and a litter of dead leaves.
  • Do you want an espalier to hide a wall or an unwanted view over the fence? Start tipping back lateral growths to growing leafy nodes close to the plane of desired growth. Do you want a tree or tree-like effect? Gradually trim off the lower growth as it becomes shaded by the upper canopy’s more recent growth. Avoid exposing young thin bark to direct blazing sun. Some light structural thinning will allow for dappled light to reclaim the growing space below, which now becomes the start of your new woodland plantings in part shade.
  • Are you after a “see-through” look from your larger shrubs to tease the eye, create some feeling of mystery and fool the senses into thinking that your gardening domain is vaster and more promising than it seems? Do you want to show off the sexy bark of your Manzanitas? Trim up the lower side shoots, and remove the inner crossing twigs and stems. Remember to step back, have that needed swig of refreshing water, and assess your work for consistency of density and form, not just within the framework of this present specimen, but also within the context of the rest of the garden. Be consistent!
  • Do you want to maintain that Channel Island Snapdragon/Galvezia as a flat and tight irrigation-free ground cover under your Coast Live Oaks but it seems to want to grow into looping arcs like a school of exuberant dolphins? Either trim these back to a ground-flat branch or, better yet, pin them down with “drift pins”– (big wire staples). Other ground-covers can also benefit from a judicious trimming of the mounding branches to thin woody centers encourage lower overall growth.

Species-specific pruning hints

  • Ceanothus should be trimmed in the dry part of the year. They are very susceptible to Apricot canker if pruned in wet weather Do not leave stubs as these are easily infected.
  • Arctostaphylos also are best pruned in dry weather. Fresh cuts are easily infected by rain splash off of bare soil, so mulch is recommended.
  • Alders are best pruned after August to avoid attracting borers.
  • Junipers and Cypresses are also best pruned in dry weather to reduce more foliage and vascular diseases.
  • Pines are best trimmed between November and October to avoid attracting the numerous species of bark boring/engraving beetles which have recently destroyed so many of our western forests. If your winter is dry, please feel free to provide supplemental irrigation at least to the normal precipitation levels for your locale.
  • Shrubs which bloom on last year’s summer buds such as Mock Orange/Philadelphus or Rubus are best pruned shortly after they finish blooming.
  • Winter deciduous woody plants will be more easily constrained in their growth if pruning is done after the major flush of leafy growth. As a rule, sucker-type growth can be greatly diminished by pruning at this stage also.
  • Oaks in the Black Oak Group, (Coast, interior, and Canyon Live Oaks, Shreve Oak and Kellogg’s Black Oak) are best pruned in the warmer, drier portion of the year: after the END of spring rains and BEFORE the fall rains begin. Roughly, late May/early June to mid-to- late-October. This is to avoid helping the pathogen, Sudden Oak Death, Phytophthora ramora –which seems to infect best in cool wet weather. If you have California Bays close to the above mentioned oaks, you might consider removing the California Bay touching the oak canopies or removing all branches that touch or shade any part of the oak canopies since the wet leaves of the Bays are excellent incubators for the active propagules of one of the reproductive stages of this aggressive organism.

More pruning techniques

  • KNOW BEFORE YOU GO. Decide what effect you want to create before you pick up your tools.
  • TIP BEFORE YOU STRIP. If a size reduction is important, do that first before you crawl inside to
    remove any inner density. It will save you frustration and embarrassment.
  • THE 4 D’s: – What to prune out when uncertainty strikes:
    • Dead – Always start here. You can’t go wrong and will get oriented to the specimen’s
      patterns of growth.
    • Damaged and…
    • Diseased – Next remove damaged and diseased growth as feasible.
    • Deranged – Remove those branches which cross or rub on another or break the pattern
      or rhythm of the rest of the structure, such as a weeping branch on an upsweeping shrub or tree or an upsweeping on a weeping form. Branches which do not make it to the outside or especially those which take a long wiggly way to get there require a lot of high maintenance “plumbing” to do the job.
  • THOU SHALT NOT MAKE STUBS. Trim back the target branch to the “collar” or swollen base of the branch, leaving the ring or partial collar belonging to the tissues of the larger limb where it appears to be trying to overgrow the target branch. Do not damage this “collar” as it is the tree’s first line of defense when the branch dies.
  • UNDERCUT HEAVY BRANCHES TO PREVENT RIPS, then make your final cuts. On more massive limbs three or more cuts might be in order.
  • BUY QUALITY TOOLS. Keep them safe, clean & sharp!
  • WEAR GLOVES & EYE PROTECTION, especially when working above your head. If using pole-saws & pole-pruners also wear a hardhat.
  • ON BIG TREES HIRE A CERTIFIED ARBORIST.

Finally, step back to enjoy the fruits of all your labors!


Watch the video: Canopy reduction tree pruning