Many homeowners use nails, screws, or staples to hang lights or decorations. Some even use metal fasteners when building treehouses in their trees. But most never stop to think about the potential damage this may cause.
The truth is, yes, nails, screws, and staples can cause significant damage to a tree.
While you probably won’t kill an otherwise healthy tree by driving a single nail into it, inserting a large number of fasteners into an already stressed tree may very well lead to decline, fungal infection, or, in extreme cases, structural issues.
Read on to learn more about the damage metal hardware can cause and what you can do to reduce the effect nails, screws, and staples have on trees.
The Damage Nails, Screws, and Staples Can Cause to Trees
Driving nails, screws, or staples into your tree can cause a host of problems that may affect the long-term health, and ultimately the safety, of a tree. A few of the specific problems these kinds of metal fasteners can cause include the following:
Permanent Damage
Trees do not “heal” like animals do; instead, they produce new wood and attempt to seal off the area — something arborists call compartmentalization. So, tree wounds are effectively permanent and, in extreme cases, may cause long-term structural weaknesses.
Providing Entry Points for Disease & Decay
The outer bark of the tree exists, in part, to protect the tree from disease and decay. When you pierce this protective layer, you create a wound that may allow decay organisms and pathogens to infect the tree — a problem best caught early through regular plant health care.
Cambial Damage
Driving a nail, screw, or staple into your tree often pierces its cambium layer. The cambium is a very thin layer of live, growing tissue that produces new cells that become either xylem, phloem or more cambium. Injuring this part of the tree can disrupt water and nutrient flow between the roots and canopy.
A Problem for People: Trees Grow Around Objects
Nails, screws, and staples aren’t only a problem for trees. They can also cause problems for humans too.
When you drive a metal fastener into a tree, the tree will try to grow around the item. Eventually, the metal pieces will often be completely enclosed in new wood.
This can present significant safety hazards for anyone who attempts to prune or remove the tree in the future using a chainsaw. In cases where embedded hardware has compromised a tree’s structural integrity, tree cabling and bracing may be necessary to stabilize it.
Arborist-Approved Methods for Attaching Items to Trees
It’s always a good idea to avoid attaching things to trees when possible. But sometimes, there’s simply no better place for a birdhouse, sign, or holiday decoration.
In these cases, you’ll want to do so in the safest and gentlest possible manner for the tree. That generally means using flexible straps, rather than metal fasteners. Make sure the strap is at least 1.5 inches wide, as this will help spread out the force and minimize any damage caused.
Just remember to keep an eye on the strap and loosen it as your tree grows over the years.
Treehouses: Dangers & Best Attachment Practices
Given that treehouses often require larger hardware and create more substantial wounds than a few small nails, they have greater potential to affect tree health.
This is true, and to the extent possible, treehouses should be designed in a manner that minimizes, if not entirely eliminates, the number of nails or screws inserted into the tree. A “treehouse” that’s really more of an elevated structure built near or around a tree is less likely to cause significant harm than one that’s physically attached to and supported by the tree.
When you must rely on the tree to provide support for the structure, try to use fewer, stronger connection points rather than driving dozens of screws into the tree. Treehouse attachment bolts (TABs) are often helpful in this regard.
Nevertheless, it is usually advisable to consult with a professional treehouse designer and an ISA-certified arborist before constructing the treehouse.
Minimizing Risk When Nails, Screws, or Staples Are Necessary
Although you’ll want to avoid using nails, screws, or staples whenever possible, there are some situations in which these kinds of fasteners are necessary. In these cases, we suggest you follow the steps below in order to reduce the negative health effects your tree will suffer from using these items:
- Don’t drive nails, screws, or staples into young trees. Young trees need to allocate their resources to producing a robust root system and canopy rather than compartmentalizing wounds. So, try to avoid using metal fasteners on trees that are less than 10 inches in diameter at breast height (approximately 4.5 feet above the ground).
- When possible, choose trees with thick bark. Thin-barked species (such as beeches and many maples) will often suffer greater damage from nails, screws, and staples than species with thick bark, including mature oaks, tuliptrees, hickories, and others. Additionally, thin barked species are also more susceptible to sunscald, presenting yet another potential complication.
- Don’t drive fasteners into trees that are already wounded or stressed. Trees have a finite amount of resources, and those that are already struggling to cope with stress, disease, wounds, woodpecker damage, or decay are less equipped to compartmentalize the wounds created by metal hardware.
- Use as few nails, screws, or staples as possible. The more holes you create, the more stress you put on the tree and the higher the risk of insect and disease issues. So, when you must use metal fasteners in a tree, try to be deliberate about the number of holes you create and look for ways to minimize the number of screws or nails inserted.
Always Provide the Support Your Trees Need to Thrive
After you damage your tree with nails, screws, or staples you will need to provide the support it needs to compartmentalize the damage and remain in good health. Ideally, you’ll contact an ISA-certified arborist to obtain guidance for your specific tree.
However, the following steps are helpful in most circumstances:
Mulch
Applying a 2- to 4-inch-thick layer of organic mulch over a tree’s root zone provides a wealth of benefits that will help support the tree. Mulch not only moderates soil temperatures and helps retain soil moisture, but it also helps reduce weed growth, protect the roots from mower damage, and improve soil structure.
Try to cover the entire root zone with mulch, starting about 6 inches from the trunk or root flare and extending at least as far as the dripline. Don’t pile mulch against the trunk and create a “mulch volcano,” as this encourages adventitious roots to form and invites decay.
Bio-Stimulants
Some bio-stimulants may help support wounded trees, as well as those that are growing in poor-quality soil — which a soil test can help identify — or simply not thriving.
There are a few different kinds of bio-stimulants available, but they all seek to accomplish the same basic goal: help your tree recover and better utilize the nutrients available to it.
Unlike fertilizers, which are often created from synthetic compounds and may even stress trees when used improperly, bio-stimulants are organic products akin to multivitamins that consist of things like beneficial bacteria, mycorrhizal fungi, and seaweed.
Water
Keeping your tree hydrated can help reduce the effects of physical injury and help the tree recover. So, consider providing supplemental water for a few weeks after inserting nails, screws, or other hardware into your trees.
Try to water deeply but infrequently, as this helps promote deep root growth. Just be sure that you don’t apply water to the tree’s trunk — especially the places where you’ve made holes. Doing so can increase the chance of fungal infection and decay.
Monitoring
No matter what kind of stress or damage a tree suffers, it’s always important to monitor it closely for red flags over the coming weeks, months, and years. If you notice any of the following signs or symptoms, contact an ISA-certified arborist and have the tree evaluated:
- Canopy dieback
- Significant insect activity
- Yellowing foliage
- Premature fall color
- Leaf drop
- Mushrooms or conks
- Easily dislodged bark
Pest Treatments
In some cases, it may be wise to have a wounded tree treated for potential or existing pest problems. This will allow the tree to allocate its resources to compartmentalizing the wound rather than battling a pest.
For example, if you have an ash tree, you should speak with a certified arborist about having it proactively treated for emerald ash borer (EAB), a deadly tree pest that’s easiest to treat early or before infestation even occurs.
Frequently Asked Questions About Nails, Screws, and Staples in Trees
Homeowners often have questions about attaching signs, decorations, birdhouses, and other items to trees. Below are answers to some of the most common questions our arborists hear regarding nails, screws, and staples in trees.
Is it OK to put a nail in a tree?
A single nail in a healthy, mature tree is unlikely to cause significant harm. However, every nail creates a wound that the tree must compartmentalize. Repeatedly driving nails, screws, or staples into a tree increases stress and creates additional opportunities for insects, diseases, and decay organisms to enter.
Are screws better for trees than nails?
Not necessarily. It’s a tradeoff in many cases. Screws provide better anchorage, which may reduce the number of fasteners needed. But screws often require a larger hole than a nail. In either situation, the goal should be to use as few fasteners as possible and install them properly.
Can a tree recover from nail or screw damage?
In many cases, yes. Trees are remarkably resilient and can often compartmentalize small wounds successfully. Healthy trees generally recover from minor hardware damage without long-term problems, while stressed, diseased, or declining trees may have more difficulty responding to injuries.
Should I remove old nails or screws from a tree?
Not always. Removing embedded hardware creates a new wound and can sometimes cause more damage than leaving it in place. If the hardware is not creating a safety issue, it may be best to leave it alone. A certified arborist performing routine pruning can assess the situation and advise accordingly.
What is the safest way to hang something from a tree?
Whenever possible, use wide, flexible straps rather than nails, screws, or staples. Straps help distribute pressure over a larger area and avoid creating wounds in the trunk. Be sure to inspect and loosen the straps periodically to prevent them from girdling the tree as it grows.
Can nails or screws cause a tree to die?
It is very unlikely that a single nail or screw will kill a healthy tree. However, numerous wounds, large hardware installations, or injuries to trees that are already stressed or declining can contribute to health problems and increase the risk of decay over time — and in severe cases, may ultimately necessitate tree removal.
Are rusty nails bad for trees?
Rust itself is generally not harmful to trees. The primary concern is the wound created by the nail rather than the corrosion that develops over time. However, rusty nails can still become embedded in the trunk and create hazards for future pruning or removal work.
RTEC Treecare: Here When You Need Us
Even though it’s wise to avoid inserting nails, screws, or other fasteners into trees, we understand that homeowners sometimes have no choice. And in some cases, the nails may have been driven into the tree by a previous owner, leaving you responsible for protecting its ongoing health.
In either case, the professional arborists at RTEC Treecare are here to help. Contact us today to have your tree assessed and receive a custom action plan, designed to support your tree and give it the best chance of thriving for years to come.
