Series: Storm Season / El Niño Prep (Part 3)
What should property managers look for before winter storms? Start with four things: dead or weak limbs, weak branch connections, signs of root trouble, and what sits underneath each tree. With a very strong El Niño forecast, saturated soil can loosen a tree’s grip on the ground, so a tree that has stood for decades can fail with little warning. Checking now, while the ground is still dry, costs far less than responding to a failure in January.
This is Part 3 of our storm-prep series, following Drainage 101: Spot Problems Before the Rain Does and A Super El Niño Is Coming: Is Your Property Ready? Drainage problems are mostly about water. Tree problems are about safety and liability, which is why this topic gets a full article of its own.
Know a property manager or facility manager with mature trees on site? Share this guide with them before the first storm.
Why a Strong El Niño Raises Tree Risk
NOAA’s Climate Prediction Center puts the chance of a very strong El Niño this fall and winter above 90%, with a 75% chance that the October to December season will exceed every El Niño on record since 1950. For Bay Area properties, the wettest signal falls in January through March, when soil is already full from earlier storms.
That matters because trees depend on soil to hold their roots in place. When soil is saturated, water takes up the space between soil particles and carries part of the load that the soil would normally carry. As a result, roots lose grip, and a compromised tree can fall even when the wind is not especially strong. In addition, back-to-back storms repeat that wind load on ground that never has time to firm up.
The Four Things to Check
1. Weak Limbs and Branch Connections
What to look for:
- Dead branches, and limbs that are cracked, split, or hanging.
- Codominant stems, where two trunks of similar size grow from the same point and compete.
- Included bark, a seam of bark trapped inside a branch union. It leaves a narrow, weak connection that can split as the limbs grow heavier.
- Heavy limbs that extend over parking, entries, walkways, or play areas.
Quick check: Walk the canopy line with binoculars and note any limb over a place where people or vehicles pass.
2. Root Problems
What to look for:
- Soil that is heaved or mounded on the side opposite a lean. This can mean roots are pulling out of the ground.
- A new lean, or a lean that has increased since last year.
- Mushrooms or conks at the base of the trunk or along the root flare, which often indicate internal decay.
- Roots cut or damaged by trenching, paving, irrigation, or utility work.
- Soil or mulch piled high against the trunk, and shallow roots at the surface.
Quick check: Take dated photos of each tree base now. Next month, compare them. A lean that changes is a reason to call a professional immediately.
3. Wind Exposure
What to look for:
- Trees on ridgelines, slopes, or the open edge of a parking lot.
- Trees that were recently sheltered by a neighboring tree or building that has since been removed.
- Recently planted or transplanted trees, which have shallower root systems and are more likely to lean in strong wind.
Quick check: Ask which direction winter storms usually come from on your site, then look at the trees on that side first.
4. What Is Underneath: The Targets
A weak tree over an empty planting bed and the same tree over a main entrance carry very different consequences. Professional risk assessments weigh both the likelihood of failure and what the tree would hit, so list the cars, doors, walkways, play areas, utility lines, and buildings under each canopy. In practice, that list tells you which trees to deal with first.
The Liability Angle Property Managers Should Understand
California courts apply a negligence standard to tree failures. In general, an owner is not automatically responsible just because a tree falls. Instead, the question is usually whether the owner knew, or should have known, about a hazard and failed to act reasonably. Visible warning signs such as dead branches, rot, fungal growth at the base, a significant lean, or earlier limb failures can show that a problem was knowable. Ownership generally follows where the trunk stands, so trees along property lines deserve attention too.
On the other hand, when a healthy, properly maintained tree fails in a severe storm, courts have generally found no liability, often treating it as an act of nature. In other words, the question is less “did a tree fall?” and more “what did we know, and what did we do about it?”
For that reason, documentation matters. Dated inspection notes, photos, arborist reports, work orders, and pruning invoices help show that your team exercised reasonable care. They also give your insurance carrier a clear record if a claim ever arises.
A note on scope: This is general information, not legal advice. Talk with your attorney and your insurance carrier about your specific obligations.
Save this section for your next risk review, and share it with your insurance contact.
What a Professional Tree Risk Assessment Includes
The International Society of Arboriculture (ISA) trains arborists through its Tree Risk Assessment Qualification (TRAQ) to follow a consistent method. Assessments are described in levels:
- Level 1, limited visual: a walk-by or drive-by that looks for prominent issues such as large dead trees, severe leans, or hanging limbs. Property managers with many trees often use it to screen quickly and set priorities.
- Level 2, basic: the standard professional evaluation, where a qualified arborist inspects each tree on the ground, including its base, trunk, and canopy.
- Level 3, advanced: a deeper investigation of a specific tree using additional tools when a Level 2 finding calls for it.
A good assessment documents the targets, the defects, the likelihood of failure, the consequences, and the options for reducing risk. Ultimately, that report gives you something specific to act on and to file.
Before You Cut: Check Your City’s Tree Rules
Many Bay Area cities protect certain trees, so removing one without a permit can create a different kind of problem. For example, Concord requires a permit to remove protected trees, including native oaks, California bay, buckeye, and sycamore at 12 inches in diameter and other trees at 24 inches, measured 54 inches above the ground. Walnut Creek protects trees with a trunk circumference of 28 inches or more, about 9 inches in diameter. Danville protects heritage trees and certain species.
Cities generally allow emergency removal of a hazardous tree, but they usually want written approval. Because rules differ by city and change over time, confirm the current requirements with your city before any removal.
Property Manager Tree Risk Checklist
☐ Walk every tree near buildings, parking, walkways, play areas, and entries
☐ Note dead, cracked, or hanging limbs, and any limb over a target
☐ Look for codominant stems and included bark at branch unions
☐ Check each base for mushrooms, conks, heaved soil, or a new or increased lean
☐ Look for root damage from trenching, paving, or utility work
☐ Identify trees that are newly exposed to wind or recently planted
☐ Photograph every concern with the date and location
☐ Rank concerns by what sits underneath
☐ Request a qualified arborist assessment for anything on this list
☐ Confirm local permit requirements before any removal
☐ File the notes, photos, and reports where your team can find them
Not sure what you are looking at? Request a pre-storm walkthrough and we will help you sort what can wait from what cannot. Contact Rubicon Landscape Group.
Common Mistakes to Avoid
- Waiting for the first storm. Once the first serious storm makes the news, every property in the Bay Area calls for the same services at the same time.
- Checking only from a distance. Roots and the base of the trunk need a close look.
- Pruning without a plan. Topping a tree, which means cutting main branches back to stubs, creates weakly attached regrowth and is not recommended.
- Skipping the paperwork. Work that is not documented is hard to prove later.
- Ignoring trees at the property edge. A neighbor’s fence or a public sidewalk is a target too.
Quick Answers
Who is responsible when a tree falls on a commercial property in California?
Ownership generally follows where the trunk stands. Responsibility for damage usually turns on negligence, meaning whether the owner knew or should have known about a hazard and failed to act reasonably. Talk with your attorney and insurer about your situation.
How often should commercial property trees be inspected?
As a practical standard, we recommend a walkthrough at least once a year and again after any major storm, with closer attention to trees that have known defects or that stand over busy areas.
Can saturated soil cause a healthy-looking tree to fall?
Yes. Saturated soil reduces how firmly roots are held, and the risk is higher for trees that already have root damage, decay, or a lean. A tree can look healthy from the canopy while its roots are not.
Who should assess a tree I am worried about?
Look for an ISA Certified Arborist who also holds the ISA Tree Risk Assessment Qualification (TRAQ). Ask for a written report.
What Comes Next in the Series
Next, we look at drainage upgrades: what French drains, catch basins, and retention basins each solve, and when to install them. If you have not read Part 1 and Part 2 yet, start with A Super El Niño Is Coming and Drainage 101. Follow Rubicon for the rest of the series.
Ready to Check Your Trees Before the Rain?
Schedule a pre-storm property walkthrough with Rubicon. We will review your trees, drainage, and slopes together, flag what needs attention, and help coordinate a qualified arborist assessment where one is warranted.
Resources for Going Deeper
- Save Our Water: California’s statewide water conservation program, including outdoor watering guidance
- QWEL (Qualified Water Efficient Landscaper): EPA WaterSense-recognized certification covering irrigation auditing and system design
- NALP (National Association of Landscape Professionals): industry certification and continuing education for landscape and irrigation professionals
- CLCA (California Landscape Contractors Association): California-specific water management certification and continuing education
Why Rubicon
For more than 30 years, Rubicon Landscape has provided dependable, professional landscape services throughout the Bay Area, helping property owners and managers maintain landscapes that are healthy, attractive, and reliably well-functioning.
Our approach is built on quality workmanship, responsive service, and proactive problem-solving, the kind of long-term partnership that protects your landscape investment and delivers consistent results, year after year.
As a division of Rubicon Programs, that work also creates real community impact. Every project supports employment opportunities and workforce development that strengthen the communities we serve.
Professional landscape services. Reliable results. Meaningful community impact.
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From commercial properties and municipal facilities to institutional sites and multi-site portfolios, our services include:
- Commercial Landscape Maintenance & Installation
- Landscape Construction & Renovation
- Irrigation Installation, Repair & Management
- Water Efficiency & Conservation Solutions
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