Tree pruning: common questions
Want to know more about the why, when, what, where and how of tree pruning? Read on to learn more about how to keep your tree shapely and in tip-top condition.
The Why
- Why is it important to prune the trees in your yard?
- Here are three great reasons to prune your trees: it helps ensure the safety of people and property, promotes tree health and strong branch structure and improves the aesthetics of both the tree and the overall view.
- Trees in the woods do just fine with no pruning. Why interfere with nature?
- Trees in a forest often self-prune branches that don’t get enough sunlight. No, they don’t take a saw to their limbs. Leaves are the trees’ food factories, and if they don’t get enough sunlight they can’t create energy to support the branch. The branch then dies over time and falls off. While a falling branch in the woods may only affect the trees around it, unexpected falling branches in a yard are another story. Proper pruning reduces the risk of branches falling and hurting a person or a nearby structure.
The When
- What time of year should I prune?
- It’s best to prune in February and March, just before spring growth starts. During this time diseases and insects are inactive, but it’s nearly time for trees to start growing and sealing off wounds. The smaller the cut the better the chance the tree will close the wound completely. And remember: never prune oak trees between April and June, as this is the high-risk season for oak wilt disease transmission.
- But dead branches and tree issues are more noticeable in the summer—how bad is it really if I just take care of pruning then?
- Trees capture and store energy in the summer. If you cut leaves off while they are busy capturing energy, you deprive the tree of the ability to store those nutrients for the winter. Summer is also stressful for most plants due to water loss, and you’re taking a risk with insects and disease. Only prune if you have an immediate safety or property damage concern. Contact a certified arborist to determine if special precautions should be made to protect the health of the tree.
- Is there anything I can do during the growing season?
- The growing season is ideal for lots of tree-related activities that don’t include pruning! Here are just a few:
Before pruning
After pruning- Mulch and water your most important trees.
- Take a walk through your yard during the summer months just to look at your trees. Do you notice any branches that could create a safety or property damage risk in the future? Note the location and issues on your November calendar—it will help jog your memory later when trees lose their leaves and you’re ready to prune.
- In late fall, as trees lose their last leaves and you can see the tree structure more clearly, walk around your yard again and examine your trees for visible indicators that your trees need to be pruned, or even removed.
- Check if your newly planted trees have multiple branch leaders that are competing at the top of the tree. As the competing tree branches grow, they will not fuse together, but instead will rub and push against each other, creating a structural weakness in the tree.
- If you see large holes on the trunk of the tree, call a certified arborist who can determine the level of risk it has of failing. They will take into consideration the species of the tree, the extent of the decay and the tree’s location in your yard.
The Who
- I’m sure I can handle pruning that tree with a ladder. Why hire an arborist?
- If you can remove a branch with a hand pruner or handsaw from the ground or by using a small “orchard” ladder (a special three-legged ladder), then you can complete the pruning work yourself. However, if you have to get on a large ladder or use a chainsaw to prune a branch, then consider hiring a certified arborist. These two criteria can indicate a large tree, and you can do a lot of damage to the tree and yourself. Never prune trees near or under utility lines—instead, contact Xcel Energy for assistance.
- How do I find a certified arborist?
- Visit the hiring a tree care professional page. Or, visit msa-live.org.
The How
- How often should I prune my tree?
- The answer depends on the species of the tree. Species with fast growth rates such as maples and aspen will need more frequent pruning when young to maintain one central leader and well spaced branches. In general, from planting until 25 years you should plan to prune the tree 7–10 times.
- How much should I remove each time I prune?
- Slower growing species such as ironwood and redbud should be pruned more carefully than faster growing species. In general, remove no more than 25% live branches per year.
- What should I be watching for if I plan to prune my small tree?
- Follow these tips when pruning your small tree.
- Pruning lower branches of a tree, or “raising the crown,” can create better clearance for vehicles and mowing. But don’t let this be the end of your pruning!
- Does your newly planted tree have multiple branch leaders at the top? If so, the competing branches will not fuse together, but will push against each other, creating a structural weakness in the tree. Remove or reduce the length of the competing branches so that they are subordinate to a main leader.
- Pruning now to improve the structure of the tree when it is young means you make many small cuts that the tree can seal over. Large pruning cuts may not seal over completely, allowing decay organisms to break down the wood. This often manifests as a wound or hole in the tree.
- Assess the overall structure of the tree. Does it have a strong central leader? Remove extra branches that are competing with the best branch leader.
- Remove any dead, decaying, cracked or diseased branches. Making a proper cut will encourage better wound closure.
- Remove branches that create sightline threats near the driveway or entryway to your house.
- Select the strongest branches and remove any crossing or rubbing branches.
- When cutting, favor branches with U-shaped unions and, when possible, remove those with V-shaped unions because they are not structurally sound. Poor branch unions can lead to decay, cracks and splitting later.
- In certain species like crabapple or fruit trees, thinning the crown of a tree can increase the air flow in the canopy, which can make it less susceptible to fungal diseases. However, thinning doesn’t mean removing all the inner branches and leaving a lion’s tail tuft at the tips of each branch; instead reduce the density of the branches in the canopy.
- What tools should I use?
Follow these rules of thumb to determine the correct pruning tools.
At top is a bypass pruner, middle is a folding hand saw, bottom is a hand saw.- Branch diameter 1 inch and under
- By-pass hand pruner.
- Branch diameter up to 2 inches
- Consider loppers. Loppers look like a hand pruner, with longer handles for better leverage and a slightly larger blade.
- Branches up to 4 inches
- Hand saw
- Branches/limbs greater than four inches
- Use a chainsaw with caution
- Pole pruner
- A tool that will allow you to reach and prune branches higher in the canopy of the tree, but only cut branches four inches and under with this device.
- Where should I make my pruning cut?
Cut branch tissues, not stem (trunk) tissue. To avoid cutting the stem, find the branch bark ridge and the branch collar, a slightly raised area visible on the underside of the branch were it meets the stem. This is the area where stem tissue and branch tissue merge, and it’s important to cut the branch just outside the branch bark ridge and branch collar.
Pruning cut made outside branch bark ridge and branch collar.- Why is a proper cut important?
The proper cut helps the pruning wound to seal efficiently. Do not make a cut flush to the tree stem. The pruning wound will not seal correctly and will allow decay organisms to enter the tree. Avoid leaving a branch stub, it will take more energy for the tree to seal over the wound and keep decay from spreading into the tree.
Fully sealed over wound
after pruning cut.- What is the three-cut method?
The three-cut method is useful for pruning living branches, because it prevents bark ripping that can occur when a branch is cut just once. The first cut is a shallow notch made on the underside of the branch, outside the branch collar. This prevents a falling branch from tearing the stem tissue as it pulls away from the tree. The second cut should be outside the first cut (toward the branch tip), all the way through the branch, leaving a short stub. The third cut removes the branch stub. Make a final cut just outside the branch bark ridge/branch collar.
Diagram of three-cut method.- Do I need to spray the pruning cut?
- The only time pruning wounds have to be covered is when you are cleaning up a storm damaged branch/limb on an oak tree during the high-risk season for oak wilt. In these instances, paint on a water-based paint (no tar or spray paint) within the first 15 minutes of making a clean cut. In all other instances, trees naturally seal over wounds and compartmentalize decay as long as they have a good pruning cut!
Branch before cut
(ForestryImages.com)
Branch after cut
(ForestryImages.com)
