HOME with Dean Sharp: How to Prune a Tree


Beautiful autumn colours are seen across the Royal Botanical Gardens

Beautiful autumn colours are seen across the Royal Botanical Gardens

PHOTO CREDIT: Getty Images

It’s Fall … Time to Prune!

Well, it's that time again! It's time to get pruning! Proper pruning can actually extend the life and health of a tree. That's great news! Now, here's the bad news -- improper pruning can really hurt a tree. So be careful. Know what you are doing before you pick up those shears.

Here are several important points from Dean to keep in mind when it comes to pruning:

  • Pruning will change the form and growth rate of a plant.
  • Pruning can minimize and help prevent insect and disease damage.
  • Problems may be prevented by pruning correctly during the formative years.
  • Encourages flowering and fruit development.
  • Pruning should start at planting

How to Prune Large Branches - Master the Three Cuts

1.The Undercut - A few inches away from the trunk on the underside of the branch and about ¼ of the diameter deep. In case the branch splits and tears, this stops the tear from stripping bark down the trunk.
2.The Main - Starts directly above the undercut and comes all the way through. This removes the branch.
3.The Trim - Now that the weight of the branch is gone you can safely trim the remaining stub.

Remember, a flush cut is too large (oval). You need to cut nearly flush to the bark on top of branch and angle away gently to keep cut as small and circular as possible - you want a bump, not a stump!

How to Prune Small Branches

  • To shorten a branch or twig, cut it back to a side branch or make the cut about 1/4 inch above a bud.
  • Always prune above a bud facing the outside of a plant to force the new branch to grow in that direction.

Trees don’t heal, they seal - bark forms a “callus” doughnut

Trees don’t heal like people. When a cell is damaged, a tree cannot go back and fix or replace it. But it can limit the damage by containing it and excommunicating it from the rest of the still-growing tree. The trick is in sealing, not healing. The focus is on resisting the spread of damage – especially infections of bacteria and fungi and the decay they cause – by isolating the wound and then growing beyond it. We cover a cut with Neosporin and cover it with a bandage, but this is NOT helpful to a tree. Tree paint or tar or other “pruning dressings”– while a great temptation to tree lovers everywhere – actually interferes with the normal progression of a tree’s wound response and should be avoided. Many such products are petroleum or even asphalt based and may hold moisture, mildew, and fungus against a wound without letting it dry out. Trees need to seal and close, and generally they do this much better without additives.

What to prune?

  • Remove branches that rub together.
  • Remove any downward-growing branches.
  • Remove branch stubs
  • Remove branches that grow inward
  • Avoid topping trees. Never prune the leader.
  • Remove diseased or dead branches.
  • Remove Narrow-angled branches - most likely to split
  • If two limbs are crossed, entangled or otherwise competing, remove one of them completely at its base.
  • Remove any limbs along the trunk that are bigger in diameter than the trunk.
  • Remove suckers coming up from the roots or low on the trunk.
  • Remove those crazy vertical branches that aren’t the main leader - “watersprouts”
  • Remove “suckers” (like water sprouts but coming up from the roots) both suckers and watersprouts have weak connections to the old wood.

The Goal

Appearance in the landscape is essential to a plant's usefulness. For most landscapes, a plant's natural form is best. Avoid shearing shrubs into tight geometrical forms unless they need to be confined or trained for a specific purpose. When plants are properly pruned, it's hard to tell that they've been pruned. 

PHOTO CREDIT: Anton Darius on Unsplash

The Right Tools

  • Sharp tools are safe tools
  • A good pair of pruning shears is probably one of the most important tools. Cuts up to 3/4 inches in diameter.
  • Loppers are long handled pruning shears with greater leverage for branches up to 1½ inches in diameter.
  • Hedge shears are meant only for pruning hedges, nothing else. They cut small stems best.
  • Hand saws are very important for cutting branches over 1 inch in diameter. Many types of hand saws are available. Special tri-cut or razor tooth pruning saws cut through larger branches – up to 4 inches in diameter – with ease.
  • Pole saws and loppers allow for extended reach with a long handle.
  • Chain saws - Operators must wear protective clothing and exercise caution when using them. Never use chain saws to reach above your shoulders, or when you are on a ladder.

Changing Southern California with Trees

Trees and vegetation lower surface and air temperatures by providing shade and through evapotranspiration. Shaded surfaces may be 20–45°F cooler than unshaded and evapotranspiration can help reduce peak summer temperatures by 2–9°F Also, trees (especially fruit trees) can fireproof a region.

Benefits and Costs

  • Reduced energy use: Shade decrease demand for air conditioning.
  • Improved air quality and lower greenhouse gas emissions. They also remove air pollutants and store and sequester carbon dioxide.
  • Enhanced storm water management and water quality: Vegetation reduces runoff and improves water quality by absorbing and filtering rainwater.
  • Reduced pavement maintenance: Tree shade can slow deterioration of street pavement, decreasing the amount of maintenance needed.
  • Improved quality of life: Trees and vegetation provide aesthetic value, habitat for many species, and can reduce noise.

Financial Benefits:

  • The primary costs of maintaining trees or other vegetation include purchasing materials, initial planting, pruning, pest and disease control, irrigation.
  • A five-city study found that, on a per-tree basis, the cities accrued benefits of $1.50–$3.00 for every dollar invested in trees.
  • Personal financial benefits: Well established that good landscaping has a 110% ROI. HGTV reports that several recent nationwide surveys show mature trees in a well-landscaped yard increase the value of a house by anywhere from 7% to 19%.
  • Median home price of $550,000. 7% = $38,500. 19% = $104,000. So … the best ROI on your home is to buy a giant $15,000 specimen tree because it will double in value as soon as its in the ground.

Keyword - Dormancy

Happens to ALL trees - tree rings prove it. What causes changing colors of leaves? Chlorophyll production (green) is shut down and absorbed back into the tree. Take a look at a changing leaf and you’ll see green in the veins. Carotenoids (sunblock) begin to show through. Anthocyanins produced in autumn protect against being eaten. Once the leaf has been drained of its chlorophyll the stem is sealed off and drops. Dormancy means a tree experiences less shock because it’s not trying to produce - Like being in twilight sleep at the dentist.

Pruning

Don’t top trees! It mutilates the graceful gradual tapering of branches. Topping the tree will not shorten the tree, but rather it will make the tree unhealthy and unstable. What you need to do is first clear out internally facing branches and lift edges of canopy. Then cut back cracked/damaged branches for wind and rain. Don’t trim flush with trunk or leave too long.

Here are a few pruning steps:

1.Find the “branch collar” or “bark collar” where smooth branch and trunk bark meet.
2.Start with a relief cut underneath about 2’ off trunk and ¼ of the way through - to keep branch from cracking and peeling into trunk bark
3.Cut branch through a foot or so above relief cut
4.Cut remaining stub at branch collar line.

*A properly healing tree makes a trunk lump and starts with a bark doughnut.

Planting

Old gardening axiom that says the key to growing a great plant is to put a 50-cent specimen in a $5 hole. The hole should be depth of the root ball (to prevent settling) and 3 times the width. Soil amendments have limited effect, so just put the soil back in the hole, loosely packed, and use the extra for a watering berm. Water soon after planting and every day for several weeks afterward.Deep water from at least 2 sides to bottom of hole via watering steaks or drainage pipe. Then gradually reduce the frequency of watering. Fertilizer is also of marginal benefit at planting time, and can even be harmful, so wait until the following year. A 3-inch layer of mulch around the base of the tree will keep weeds out and reduce water loss. Stake your tree - steaks should go 2’ deep. 2 or 3 stakes at slight angle in toward tree. Tie loosely enough that tree won’t blow over but can sway enough to develop its own support roots.

Mulch

Mulch is any material spread over the surface of the soil as a covering. It retains moisture in the soil, suppresses weeds, keeps the soil cool in summer and warm in winter. Organic mulch improves fertility as it decomposes. Remember, mulch is not compost, but compost can be used as mulch.

Feed

Slow release fertilizer - favorite: soil builders like worm castings.

Water

Roots grow toward water - water deep & regular - ultimately trees will find their own.

Protect

Prevent gnawing by critters looking for nest bark wounds and wrap trunks in no traction collars.

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For more great tips from Dean on pruning, listen to the entire show here!