How a Common Landscape Habit Became a Fire Hazard — and Why Gardens Are the Answer
1. Franklin, Firefighters & the Words That Stopped Me Cold
While working with the City of Franklin’s planning team on a pollinator garden project, I happened to be watching the Fire Department’s monthly Instagram update from their battalion chief. In it, I heard the words “combustible mulch” linked to a million-dollar structure fire — and it stopped me cold.
The fire, on July 5, 2025, tore through Granite City Food & Brewery here in Franklin. Franklin Fire Marshal Andy King said investigators believe it started in mulch beside the building and spread into framing hidden behind the stone veneer. Damage estimates hovered near $1 million.
In 20 years of professional garden design, I’d never heard “combustible mulch” used in a fire investigation. Yet the more I dug, the more obvious the danger became: mulch isn’t just overused and ecologically hollow. In the way it’s commonly applied, it’s burning down buildings and homes.
2. Gardens Are for Plants, Not Mulch
I’ve said it for years: gardens are for plants. Not for mulch.
But across the United States, the default landscaping formula is predictable:
Shrub — tree — some mulch. Shrub — shrub — tree — some mulch.
The result is mulch-dominated beds: 80 to 90 percent bare, lifeless surface with islands of plant life scattered through it. This is true from suburban homes to commercial plazas to HOA entrances.
In the South, our late summers are often dry. Even with occasional afternoon storms, August and September produce long stretches of hot, low-humidity days. Dry mulch in these conditions is essentially a contiguous strip of fuel that wraps around buildings.
This isn’t an accident of bad taste — it’s the result of an entrenched industry habit. Mulch is easy to install, easy to refresh, and easy to bill for. It’s become an aesthetic shorthand for “finished landscape,” even if it does nothing for soil health, biodiversity, or safety.
3. What “Combustible Mulch” Means
Any groundcover material that will ignite and sustain fire is combustible mulch. That includes:
• Shredded hardwood mulch
• Bark nuggets
• Pine chips
• Pine straw (pine needles)
• Shredded cedar mulch
• Rubber mulch
• Regional chip blends like “Tahoe chips”
Resinous species like pine and cedar burn hotter and faster. Fine, loose mulch textures let oxygen feed the fire. Even hardwood bark, while slower to ignite, can smolder long enough to ignite siding or decking.
4. How Mulch Fires Start and Spread
Fire officials describe a three-step pattern in mulch fires:
1. Ignition — Often a discarded cigarette, hot grill ember, or radiant heat from exterior equipment.
2. Smoldering — Mulch can burn invisibly beneath the surface for hours before breaking into open flame.
3. Spread — Once flames emerge, they can climb walls, get behind veneers, and ignite framing.
Mulch fires don’t need high winds or wildland fuels to cause catastrophic loss. They can start inches from a doorway on a calm day.
5. The Research — West Coast Data, East Coast Gap
The UC/Nevada Cooperative Extension Tests
Eight mulch types were tested under hot, dry, windy conditions:
• Highest hazard: shredded rubber, pine needles, shredded western red cedar
• Moderate: pine bark nuggets, Tahoe chips (pine/bark/needle mix)
• Lower hazard: composted wood chips, single-layer Tahoe chips
• Retardant-treated: delayed ignition 5–10 minutes before burning like untreated
The conclusion was blunt:
“All mulches are combustible. Some ignite faster, burn hotter, or spread more rapidly — but none are noncombustible.” — UC/Nevada Extension, 2011
The Missing Eastern/Southern Studies
No comparable lab testing exists for East Coast and Southern mulch products — where pine bark nuggets, pine straw, and hardwood bark dominate. But field incidents leave little doubt that these materials pose similar or greater risks.
6. Case Studies — Real Fires, Real Losses
2007 – Raleigh, NC
A cigarette discarded into pine straw mulch outside a townhouse complex ignited a fire that destroyed 38 townhomes. Losses exceeded $2 million.
“The fire spread with alarming speed along the pine straw beds, directly into siding and attic spaces.” — Raleigh Fire Department report
This event became a cautionary case study for pine straw hazards in the Southeast.
~2020 – Apex, NC
A similar blaze destroyed 6 townhouses in Apex. The culprit was again pine straw used as decorative mulch near combustible exteriors. In response, Apex passed an ordinance banning pine straw within 10 feet of buildings with combustible siding.
2008–2013 – Harrisonburg, VA
From January 2008 to December 2013, the Harrisonburg Fire Department recorded:
• 206 mulch fires
• 16 extended to structures
• Over $1 million in property damage
• Multiple displacements and injuries
“These are preventable fires. Keep combustible mulch away from combustible structures.” — Harrisonburg Fire Marshal’s Office
~2021 – Loudoun County, VA
A home was heavily damaged after mulch near the foundation ignited — suspected spontaneous combustion from heat buildup in a thick bed.
“Mulch can generate enough internal heat to ignite without an outside flame source. It’s rare, but it happens.” — Loudoun County Fire Marshal’s Office
Chapel Hill, NC – Demonstration
Firefighters staged a side-by-side burn test:
• Pine straw ignited fully in under 3 minutes
• Hardwood mulch smoldered but did not flame out in that time frame
The visual contrast was enough to convince local officials to recommend against pine straw near buildings.
7. Policy Response — When States and Cities Said “Enough”
• 2012 — Massachusetts: Statewide ban on mulch within 18 inches of combustible exteriors for most occupancies.
• 2025 — New Jersey: Similar rule takes effect April 15, 2025.
• Local actions: Apex, NC bans pine straw within 10 feet of combustible buildings; multiple NC cities have advisories against it.
These aren’t fringe rules — they’re in two of America’s most densely populated states and fire-prone Southern cities.
8. Why We Still Use It
• Low-skill installation: Spread it and it looks “done.”
• Recurring revenue: Refreshing mulch annually is billable work.
• Entrenched specs: Bid templates have called for mulch for decades.
• Lack of awareness: “Combustible mulch” isn’t in most homeowners’ vocabulary until after a fire.
9. What a Fire-Safe Garden Looks Like
• 0–5 feet from buildings: Create a garden. Living plants, the end.
• Beyond 5 feet: If mulched, use aged organic matter — composted wood chips, leaf litter, other decomposed plant material with lower flammability.
Dense planting not only prevents ignition but also:
• Shades soil and retains moisture
• Suppresses weeds without bare mulch beds
• Supports pollinators and biodiversity
10. Gardens as Prevention and Promise
The pollinator garden we’re designing for Franklin’s fire station will be a living example of safety and beauty working together. By replacing mulch with life, we cut fire risk, improve ecological value, and offer firefighters — and the public — a place to see that change is possible.
11. Conclusion — The End of Mulch as Default
Franklin’s July fire isn’t an outlier. Mulch fires happen every year, in every state. They destroy homes, businesses, and in some cases, lives. And they’re avoidable.
Gardens are the answer, not mulch.
Dense, living, layered plantings near buildings keep the soil cool, the pollinators fed, and the siding safe.
It’s time to end the habit of wrapping our buildings in fuel. Let’s replace it with gardens that protect, feed, and inspire.