An Introduction to Supplemental Tree-Support Systems, Part 3: How to Brace, Guy or Prop, With a Look at Related Equipment
In Part 2 of this series, we explored the deployment of steel and dynamic cable systems as risk-mitigation solutions for damaged trees or those with mechanical vulnerabilities. In Part 3, we will focus on another primary method of supplemental support: bracing. We also will touch briefly on guying and propping.

This historic northern catalpa tree on the Lindenwood University campus is supported by props, thanks to dedicated arborists preserving it. All photos courtesy of the author.
As discussed in Parts 1 and 2, supplemental support systems can be designed and installed both proactively and reactively. It’s crucial to understand the distinction between these approaches. Proactive bracing aims to prevent potential mechanical failures, while reactive bracing is applied after a tree begins to show signs of mechanical issues, such as cracking, splitting or tearing.
Before delving into the specifics of bracing, let’s address a few key points:
- Customization is key: Supplemental support systems are not a one-size-fits-all solution. Due to the vast diversity of trees and their environments, the effectiveness of these systems can vary. They should be considered complementary tools within a plant-health-care program, designed to mitigate risk to an acceptable level as determined by the client’s risk threshold.
- Alignment of risk thresholds: It is crucial that both the arborist and the client agree on the acceptable level of risk when designing and implementing these systems.
Pruning considerations: Pruning is often recommended alongside cabling, bracing, guying and propping solutions. However, arborists must carefully assess the tree’s vitality, as removing part of the canopy can negatively impact the tree’s root system and overall health. - Hardware implementation: Steel cables and rod bracing systems should always be installed with appropriate hardware. As previously stated, we only use through-hardware. When using a rod bracing system, we recommend incorporating a companion steel cable system whenever possible to provide additional support.
- Terminology clarification: In this article, the term “brace” will be used interchangeably with “rod” for the purpose of structural support. “Brace” will not refer to “cable.”

Fig. 7.8.1B: Parallel Brace System… “If multiple rods are required, we prefer to complete each rod before moving to the next location.” (excerpt from A300 text) Figure found on page 43 of ANSI A300 2023.

Fig. 7.10.3: Anchor height for guying established trees… “For ground anchors, position them at least two-thirds the distance from the ground to the height of the attachment point in the tree”. (from text) Figure found on page 45 of ANSI A300 2023.
Introduction to bracing
Arborists employ through-rods or dead-end braces to minimize movement between leaders at risk of failure, thereby reducing the risk associated with their union. A rigid brace is commonly used for already-splitting leaders, though rods or braces also can be installed proactively. As noted in the cabling segment of this series, these methods are not one-size-fits-all. Arborists must consider species characteristics, environmental conditions, tree health and client goals, while adhering to A300 standards, before implementing a supplemental support system.

Table 1 : Minimum hardware guidelines for bracing trees. (from text) Figure found on page 44 of ANSI A300 2023.
According to A300-2023, Clause 7 (formerly A300, Part 3), there are two types of rigid bracing systems: through-rods and dead-end braces. Both have their advantages and disadvantages, but for consistency, our team prefers through-rods. While there’s a debate about whether two exit holes from a through-rod are more problematic than a single exit hole from a dead-end brace, we find the engineered terminations of the through-rod system more reassuring than the hidden, harder-to-inspect, wood-biting end of a dead-end rod. Below, we outline our process for using through-rods.
It’s also important to note that the ANSI A300-2023 standard places limitations on the use of the wood-biting, lag-thread hardware used for dead-end bracing. This hardware can only be used in sound wood that is less than 10 inches in diameter. So, through-rods are required for the bigger jobs.

The Major Oak is an approximately 1,000 year old English oak (Quercus robur) found in the midst of the famous Sherwood Forest in England. This tree has numerous cables, bracing rods, props and guys working in unison to provide support for this historical behemoth. Adobe Stock photo, courtesy of the author.
Rod-installation prep
Before drilling, a detailed work plan and tree inspection are essential. It’s advisable to develop a pruning plan (A300-2023, Clause 5) to reduce leverage of overextended leaders throughout the canopy and to install a support cable (steel or dynamic) between the leaders you’re bracing. During your prework inspection, pay attention to the wood around the potentially compromised union. Assess the union for signs of decay or strength loss, or for indicators of positive wound or response wood in the area, to help refine your work plan.
Refer to the Tree Support Systems Best Management Practices (BMP) and A300-2023, Clause 7, for guidance on the minimum number of rods required and their optimal orientations. Each tree is unique and may need more than the minimums outlined in ANSI A300-2023, Table 1, or different heights and orientations compared to A300-2023, Clause 7, Figure 7.8.1 A, B or C. Figures 19 and Table 6 of the Tree Support Systems BMP provide valuable guidance and are conveniently located on the same page. As consulting arborists, we recommend bringing a copy to client meetings, and as a production arborist, it’s recommended to use it to verify rod quantities and placements.
Once your plan is set, proceed with installation. Start by following your predetermined pruning plan to reduce unwanted leverage on the target union. Next, install a cable of appropriate specifications; Part 2 of this series may be a good place to start for this! If a cable isn’t feasible, use a mechanical advantage system, such as a come-along, 5:1 rope system, rope jack or GRCS, to close the union as much as possible.
Note: Great care must be taken not to over stress an already compromised union. If installing a reactive system due to a mechanical failure, extreme caution must be taken when attempting to bring damaged sections back into alignment through positive traction.

Another view of Lindenwood University’s historic catalpa. The elaborate propping plan has mitigated enough of the tree’s mechanical risk to ensure students and faculty can enjoy this local icon for years to come.
Rod installation
With the leverage reduced and the union prepped, you can begin installing the rods.
Installing the first brace rod may seem complex, but it can be straightforward. For a single through-rod, measure the diameter of the larger leader at the target union, double this measurement and mark these points. For example, if the larger leader is 10 inches in diameter, measure 10 inches from the target union for the low side and 20 inches for the high side. Look for solid wood in this range, avoiding areas with significant decay or close to other branches. If necessary, start the project below the union for a better desired result with fewer adjustments.
If multiple rods are required, we prefer to complete each rod before moving to the next location. Once all rods are installed, inspect and adjust each termination as needed.
Equipment
The tools needed for installing through-rods are often similar to those for cabling, though larger sizes may be required. There are myriad canopy tensioning systems, but we typically employ a GRCS with, for example, a 2.6-inch swivel block, or a 4:1 or 5:1 rope pully system paired with a simple friction-management system.
For drilling, we use a half-inch right angle drill with various auger bits for larger holes longer than 24 inches or diameters exceeding five-eighths of an inch. When drilling shorter lengths (sub 24 inches) or smaller-diameter holes (half-inch and smaller), we prefer to use a seven-sixteenths-inch high-torque impact wrench. Shorter bits are useful for pilot holes, ensuring accuracy before using a full-length bit. Industry BMP guidelines require that holes be drilled completely through all sections of the tree from one direction, avoiding incomplete holes that don’t meet perfectly.
After drilling, we use machine-threaded steel rods with heavy-duty nuts and washers. If the bark is thick, a chisel or hook-billed knife may be used to carve out a “bed” for the washer to sit in to reduce any settling variability. Great care must be taken to minimize damage to the living cambium. There is no need to countersink the washer into the wood. Countersinking damages wood, without providing an engineering benefit.
After threading on a washer(s), tighten the nuts with box or crescent wrenches (high-quality ratcheting wrenches really expediate this process). Sockets also may be used if the rod is pre-cut to an appropriate length.
When installing large-diameter rods (five-eighths of an inch and greater) we use a compact bandsaw. We usually use a hacksaw or 18V multi tool with a carbide blade for smaller rods or while working from aloft. Once the rod is cut to length, we use a ball-peen hammer to peen down threads to prevent hardware from backing off. When working aloft, it is essential that you keep all hardware secured in an accessible container. Likewise, all tools should be secured with appropriate tool lanyards.
Guying
Arborists typically use guying systems to support newly planted trees, but these systems also can be crucial for intermediate and mature trees that require additional stability. Although guying systems are often temporary, some are designed to offer long-term support for trees that are mechanically compromised or have a higher risk of failure. For comprehensive guidance on guying established trees, refer to Section 7.10 of the A300-2023 and Section 6 of the accompanying BMP.
Guying systems are especially useful for trees with root or soil defects, those affected by changes in wind load due to nearby construction or tree removal or trees that have experienced acute wind throw. It is essential to assess the risk associated with such trees and determine whether guying can sufficiently mitigate this risk. If not, removal may be necessary.
When designing a guying system, there are two main anchoring methods: using a ground anchor or another tree. In either case, the guy should be installed at least halfway up the total tree’s height. When installing multiple guys, ensure the anchor hardware is spaced at least half the tree’s diameter from each guy termination.
We prefer using through-hardware for guying systems, similar to those used in cabling systems. The cable and hardware should be installed following standard cabling practices highlighted in Part 2 of this series. For ground anchors, position them at least two-thirds of the distance from the ground to the height of the attachment point in the tree. For instance, if the guy attachment is 30 feet high, the ground anchor should be at least 20 feet from the base of the tree.
If using a tree-to-tree guy system, select an anchor tree that is larger in diameter than the subject tree. Ensure that it is free of significant defects and not prone to internal rot (use caution when using species such as box elders and silver maples, etc., for those reasons). Install the anchor in the same manner as you would for cable terminations.
Finally, clearly mark ground anchors to prevent pedestrian accidents, and ensure they are placed out of reach of both pedestrians and vehicles. Tree anchors should be positioned high enough to avoid interference from pedestrian and vehicle traffic.

Although the prop holding this overextended Osage orange limb is providing adequate support, this style of prop does not adequately ensure that the branch will stay attached to the prop.
Propping
Among all supplemental support systems, props are arguably the least utilized and least researched. In essence, props are fixed structures installed to support overextended trunk or branch sections from below. Their materials and designs can vary significantly, but they are generally made from steel, wood, concrete or a combination of these materials. Proper design and construction are crucial to ensure that props can withstand the substantial loads they may encounter. When designing these systems, it is essential to consult your green-log chart and soil maps.
Beyond managing structural loads, the primary consideration when designing a prop is to ensure that the supported branch remains securely attached to it. Numerous designs and hardware solutions are available to achieve this, but it’s crucial that the prop design does not impede or restrict future growth of the tree.
Establishing a robust base for the prop can be challenging, so seeking advice from a structural engineer to determine the appropriate size and materials for the base is often beneficial. Typically, concrete footers are preferred for prop bases. Also, consider the tree species and soil type before excavation within the critical root zone of the tree.
Propping may be the most rudimentary concept of all the traditional supplemental support systems in arboriculture, but it also is faced with more complexities than the other systems.

This Osage orange tree in Old Fort Harrod State Park, Kentucky, is widely recognized as the unofficial national champion due to its unique split trunk.
Conclusion
Designing and installing bracing, guying and propping systems are crucial practices for preserving the beauty of trees while safeguarding people and property. As highlighted in previous sections of this series, there’s no universal solution for supplemental support systems. We cannot overstate the importance of consulting the A300 standards, Best Management Practices (BMPs) and arborist forums and, most important, learning from experienced colleagues.
While this guide is not exhaustive, we hope it alleviates any concerns you may have about bracing, guying and propping. We encourage you to consider incorporating these techniques into your arborist toolkit.
Andy Jones, CTSP, is an ISA Certified Arborist, production climber and co-founder of Rooted Arbor Care, a TCIA member company based in St. Louis, Missouri. He also is a member of TCI Magazine’s Editorial Advisory Committee and a presenter at TCI EXPO.
Nicholas Greenwood, CTSP, ISA Certified Arborist, is a climber in Chicago with Bartlett Tree Experts, an accredited, 49-year TCIA member.