Chamise (Adenostoma fasciculatum): chaparral fuel in rights-of-way
Chamise grows 2 to 12 feet tall, so it rarely reaches a conductor and rarely triggers a clearance measured from the wire. Its whole structure sits inside the 0 to 8 foot band of the PRC 4292 pole firebreak, where 14 CCR 1254(b) requires brush vegetation removed. It resprouts from a lignotuber after cutting.
On December 7, 2017, at 1308 hours, Southern California Edison's Clydesdale 12 kV circuit breaker at the Auld substation in Murrieta relayed and locked out. Six minutes later a crew foreman reported a fire near Los Alamos Road. CAL FIRE traced the cause to a failed mechanical pole switch, PS 2191, and put the point of origin at the base of the pole carrying it. The Liberty Fire burned about 300 acres and was contained on December 9.
The equipment that failed was at the top of the pole. What carried the fire away was at the bottom. CAL FIRE found Edison in violation of Public Resources Code section 4292, for not keeping ten feet of brush clearance around pole 2090695E. Safety and Enforcement Division carried that finding into one of the two GO 95 Rule 31.1 violations it charged, and its report sets out both.
One thing is absent from a report whose subject is vegetation at a pole base. The figure caption describes "apparent brush and grass remains at the base of the pole," and no species is named anywhere in the finding. Nothing in the rule asks for one.
That is the shape of the chamise problem. The governing number for this species is not a distance measured out from the conductor. It is ten feet on the ground, eight feet up, and the date somebody last cut it.
Twelve feet is the top of the species
Nancy E. McMurray wrote the chamise review in the Forest Service's Fire Effects Information System in August 1990. It opens with the dimension that decides everything downstream:
Chamise is a diffusely branched, resinous, native shrub from 2 and 12 feet (0.6-3.5 m) tall. Plants are unarmed, spreading, and branch very close to the ground. The many slender stems are erect and generally lack permanent branches.
Twelve feet is the ceiling. Below it, three details matter to a crew. Roughly 60 percent of chamise stems are under half an inch in diameter. The plant branches at ground level rather than carrying a clear stem. Several taproots penetrate fractured rock to depths of 10 to 12 feet, so the below-ground half of the plant is about as long as the above-ground half.
The distribution is the reason this appears on so many California circuits. FEIS calls chamise "the most characteristic and widely distributed chaparral species in California" and records that "it is present in approximately 70 percent of California chaparral."
The range runs through the Coast, Transverse and Peninsular ranges from Mendocino County to Baja California, plus the Sierra Nevada foothills and the Channel Islands. In southern California it is a dominant on outwash plains, mesas, ridges and dry south- and west-facing slopes up to 6,000 feet. Individual plants live an estimated 100 to 200 years.
A right-of-way crossing that ground is crossing chamise. The exposure it creates is a fuel exposure, and the rule that answers it is written around the pole.
The firebreak band is exactly where the species lives
Both of the clearance rules a line clearance program works to are measured outward from the conductor. GO 95 Rule 35 and its minimum distances run from the wire. PRC 4293's radial clearance runs from the wire. A shrub that tops out at 12 feet, standing on level ground under an ordinary distribution span, is not inside either one, and pruning it does nothing for either number.
The rule that reaches it is the pole firebreak. PRC 4292 requires a clearing of not less than ten feet in each direction from the outer circumference of a subject pole. A pole becomes one by carrying a switch, a fuse, a transformer, an arrester or a junction, or by standing as a dead end or a corner. Which poles qualify, and how 14 CCR 1254 turns that clearing into a cylinder, is its own subject. The layer that matters for this species is the middle one:
From 0-2.4 m (0-8 feet) above ground level--remove flammable trash, debris or other materials, grass, herbacious and brush vegetation. All limbs and foliage of living trees shall be removed up to a height of 2.4 m (8 feet).
Chamise is brush vegetation. A shrub that branches at ground level and tops out at 12 feet carries its whole stem structure through the 0-to-8-foot band, so paragraph (b) takes it at the base. A tall plant may have a few feet of crown up in paragraph (c)'s layer, and cutting the bottom eight brings that down with it.
On a tree, paragraph (b) strips the lower limbs and paragraph (c) judges what is left on condition. On this species the two paragraphs produce one outcome, which is removal, at every subject pole on brush-covered land, for every plant whose stem breaks the ten-foot line.
Two qualifications on where that bites. PRC 4296 removes any line at 750 volts or less from both 4292 and 4293. And chamise does re-enter the conductor question where the ground rises under a span, which is why 14 CCR 1256 writes sway into the PRC 4293 clearance and names its inputs:
any position through which the vegetation may sway, considering, among other things, the climatic conditions, including such things as foreseeable wind velocities and temperature, and location, height and species of the vegetation.
Location, height and species. On a cut slope below a conductor, a 10-foot shrub on ground 20 feet higher than the pole butt is a different measurement from the same shrub on the flat.
The plant's growing season sits between two clearing dates
PRC 4292 does not say how often. It requires the firebreak "during such times and in such areas as are determined to be necessary by the director or the agency which has primary responsibility for fire protection of such areas." 14 CCR 1253 answers half of that: the firebreak and clearance provisions "are applicable during the declared California Department of Forestry and Fire Protection fire season for a respective county."
Neither text sets a re-clear interval. Neither says what height of regrowth ends a clearing. The implementing article leaves both open, the utility picks them, and CAL FIRE or the Commission grades the pick after an ignition.
The plant, meanwhile, keeps a fixed calendar. FEIS records it in one line: "Stem elongation occurs from February through May." New leaves appear in late January or February. Flowers develop on the current year's growth in June, fruit ripening and dispersal finish by August, and growth has stopped well before the hot months.
Put that against a clearing date. A subject pole brushed on December 12 is clean through the winter and then sits through the one window in which the species does its entire year of height growth.
The same pole brushed on June 12 carries whatever grew back from a cut made after elongation stopped. Both crews complied with PRC 4292 on the day they worked. Only one of them left a clearing that is still a clearing in the fall, which is the season FEIS names as the species' most flammable.
That is a scheduling choice rather than a compliance one, and it belongs to whoever builds the work plan. The seasonal windows a program already works around are mostly about nesting birds and fire restrictions. This one is about the shrub.
Cutting at the ground leaves the organ that regrows it
The reason a chamise clearing does not stay cleared is structural. FEIS is direct about it:
Chamise rejuvenates its crown by continually producing new sprouts from an established lignotuber. Following disturbances such as fire or cutting, chamise sprouts vigorously from surviving adventitious buds on the lignotuber.
The lignotuber is a woody swelling at the base of the plant, and the sprouting tissue sits just under the surface. FEIS places it precisely: "Sprouts originate on the lignotuber from a narrow band of tissue located 0.2 to 1 inch (0.5-2.5 cm) below the soil surface." Between a fifth of an inch and an inch. A brush saw, a mower deck, a masticator head and a string trimmer all pass above that band.
The sprout count is large. "Large plants usually possess large lignotubers which produce as many as 500 sprouts." Most of those thin out inside the first year as the strongest stems take over, but the plant that comes back is the same individual on the same root system, not a seedling.
The published growth rates are for postfire sprouts, which is the honest caveat. FEIS reports that after fires in northern California "sprouts averaged 20 inches (50 cm) by the end of the first postfire growing season," and that growth then slows sharply, with 5-year-old sprouts at 33.6 inches and 20-year-old sprouts at only 40.4 inches.
Fire top-kills the plant and also heats the burl, and FEIS notes the perennating buds "are quite susceptible to fire damage." A cut does the first and not the second. A cut plant therefore starts its regrowth from an undamaged organ, and the first-season figure is a floor rather than a ceiling.
Three treatments change that arithmetic, and each carries its own conditions:
Treatment | What the record says | What it costs |
Cutting at ground level | Sprouts vigorously from surviving buds on the lignotuber | Cheapest, and the clearing is temporary by design |
Grubbing out the lignotuber | Removes the sprouting tissue with the plant | Soil disturbance on the slope the pole stands on |
Herbicide | FEIS records that chamise is sensitive to 2,4-D | Label, permit and a utility specification that allows it |
Browsing is a fourth and belongs in the same table only with a caveat. FEIS records that "continued close browsing kills most plants within 2 to 3 years," and that goats prefer chamise once it has been burned. Two to three years of sustained pressure is a grazing program, not a maintenance visit.
The material you cut is the ground-level standard
The same regulation that says to remove the brush says what the ground has to look like afterward. 14 CCR 1254(a) reaches:
flammable materials, including but not limited to, ground litter, duff and dead or desiccated vegetation that will allow fire to spread
Chamise cut and left inside the ten feet is dead or desiccated vegetation that will allow fire to spread. FEIS records that ether extractives in the foliage "may account for as much as 34 percent of the available heat content of chamise," and that volatile essential oils on the leaf surface ignite at low temperatures.
Those extractives do not leave when the stem dies. FEIS says what dead chamise then does in a fuelbed: "Besides igniting easily and burning fast, dead fuels preheat live fuels, further increasing stand flammability." Cured slash at a pole butt is that fuel, in a pile, under the hardware.
The clearing is finished when the material is gone, not when the cutting stops. What leaving the site clean requires, and which BMPs apply, is the paragraph that closes a 4292 unit. On a switch pole the geometry gives no margin, because the ignition source sits directly above the clearing. The Dixie Fire's ten-hour high-impedance fault needed a dry and receptive fuel bed under it before anything burned. A pole switch that fails puts sparks straight down into whatever is at the butt.
The dead fraction is a function of stand age
Chamise accumulates its own dead material and holds onto it. That is the fuel property that makes stand age, rather than plant height, the number worth writing down.
Years since the stand last burned | What FEIS records |
About 15 | Fuel loadings capable of supporting a moderately intense fire |
Within 30 | Retained dead crown material may account for 50 percent of the fuel loading |
Over 60 | Stands are sometimes termed "decadent," with dead stem biomass far exceeding live stem biomass |
The structure compounds it. Roughly 60 percent of the stems are under half an inch, and FEIS describes "large amounts of small-stemmed material, distributed continuously from ground level throughout the multistemmed canopy." Fine dead fuel, continuous from the ground up, chemically loaded, in a stand that gets worse every year nothing happens to it.
A maintained right-of-way is exactly the place stands get old. The ten feet around each subject pole is cleared on a cycle. Everything outside it sits undisturbed and keeps aging, and the seedbank thickens with it. FEIS reports seed density beneath 9-year-old stands at about 2,000 seeds per square meter, and beneath 85-year-old stands at approximately 21,000 seeds per square meter. Disturb the soil in an 85-year-old stand to grub out a burl and that is the bank being opened.
Which gives a program one field it probably does not carry: years since the last burn on the ground the pole stands on. Carried against the pole rather than the circuit, that year turns "brush at the pole" into something a planner can sort on. The system that holds the record is where it has to live, because nobody re-derives it standing in the clearing.
The chamise number is an input to a shutoff decision
The species is also the sampling standard. When a California fire agency publishes a live fuel moisture reading, it is usually a chamise reading, and utilities consume those readings directly.
San Diego Gas & Electric's amended post-event report for the January 7 to January 16, 2025 Public Safety Power Shutoff, filed February 28, 2025 in docket R.18-12-005, shows the chain end to end. On the fuels question it states:
Mid-December measurements from the Cleveland National Forest, Palomar Ranger District (PRD) indicated that live fuel moistures of new growth in chamise species were measured at 61%, while live fuel moistures in old chamise growth were at 57%. The average between the two, which is used as a data point in the FPI calculation, fell just under the critically dry threshold of 60% as defined by PRD.
Two chamise samples, 61 and 57, averaging 59 against a threshold of 60. That average feeds the Fire Potential Index. SDG&E describes the FPI as a zero-to-17 scale built from green-up, the ratio of dead to live fuel moisture, and weather, classified Normal at 0 to 11, Elevated at 12 to 14, and Extreme at 15 to 17.
The report states that a shutoff decision begins with four questions, and the third asks whether the FPI shows fuel dryness and Santa Ana winds combining at 14 or above. By the event itself, "live fuel moistures in the chamise species averaging near 55%" is one of four reasons the report gives for the Extreme rating. The amended report puts the outcome at 21,508 total customers de-energized, 15,103 of them unique.
The same threshold shows up on the sampling side. The County of Los Angeles Fire Department's Live Fuel Moisture Summary dated July 9, 2026 puts the formula and the line in two bullets. Live fuel moisture is live sample weight minus dry sample weight, divided by dry sample weight. And "60% is generally recognized as approaching a critical level of live-fuel moisture." Its chamise sites that day:
Site | Chamise LFM, July 9, 2026 |
Trippet Ranch, Topanga | 63% |
Clark Motorway, Malibu | 69% |
La Tuna Canyon, Tujunga | 69% |
Templin Highway, Castaic | 69% |
Laurel Canyon, Mt. Olympus | 73% |
Stunt Road, Calabasas | 78% |
Peach Motorway, Santa Clarita | 83% |
Glendora Ridge, Glendora | 89% |
Quigley Canyon, Santa Clarita | 93% |
Thirty points separate Trippet Ranch from Quigley Canyon on the same day inside one county. A district-average reading would have hidden that. The same summary notes that three of its historical sites were burned over between September 2024 and January 2025: Tanbark Flats in the Bridge Fire, and Schueren Road and Bitter Canyon in the Palisades and Hughes Fires.
FEIS supplies the mechanism behind the threshold. Chamise "is most flammable in the fall," and falling fuel moisture "increases the concentration of extractive chemicals." The plant does not merely dry out. It concentrates.
For a vegetation program the practical consequence is timing. A chamise reading crossing 60 percent in a district is a forecast that the clearings cut in spring are now standing in fuel that behaves differently, and it arrives weeks before the wind does.
Converting the stand trades one fuel for another
The tempting move on a chaparral right-of-way is conversion: take the chamise out of the corridor floor and hold it in something low. The rule leaves an opening for exactly that, in the 14 CCR 1255(d) exemption for vegetation kept under 12 inches, fire resistant, and planted and maintained specifically to prevent soil erosion and fire ignition. That exemption has to be proved rather than asserted, and a resprouting burl satisfies none of its three conditions.
The species record also says what usually arrives instead. FEIS notes that "on sites with relatively deep soils, decadent chamise may be replaced by annual grasses." That is a real conversion, and grass is not a safer neighbor for a pole.
The postfire revegetation experience is the warning: ryegrass seedings on burned chaparral "produce an easily ignitable fuel bed that increases the likelihood of an early reburn," and FEIS records chamise density reduced up to 97 percent after a grass fire on a one-year-old burn. Grass removes the shrub by burning more often, not by burning less.
So conversion is a maintenance commitment rather than a one-time treatment. The honest version reads as a specification: a named cover, a maintained height under 12 inches, a planting record, and a re-treatment interval. Without those four, what the corridor gets is cured annual grass at the base of a switch pole, and 1254(a) reaches that too.
What a chamise record has to carry
The Liberty Fire record contained a photograph of brush at a pole base and no species. That is the ordinary state of the evidence, and it is enough to support a 4292 finding, because the statute asks about a clearing rather than about a plant. A program that wants to schedule the work rather than answer for it afterward needs more than the rule requires.
Field | What goes in it |
Pole ID and subject-pole reason | The hardware that brings it under 4292: switch, fuse, transformer, arrester, junction, dead end or corner |
Date cleared | Month and day, because the February-to-May elongation window falls between two of them |
Method | Cut at ground level, grubbed, masticated, or treated, named per pole |
Species inside the ten feet | Chamise, and whatever else is in the cylinder |
Regrowth height at the last look | Inches, with the date it was measured |
Stand age outside the clearing | Years since the last fire on that ground |
Disposal | Where the cut material went, and whether any stayed inside the ten feet |
Four of those seven are dates or measurements that go stale on the plant's schedule rather than the program's. What a closed unit has to show covers the form. The species supplies the reason any of it has to be re-read. Chamise clears completely, then comes back from a fifth of an inch below the surface. What separates a compliant pole from a non-compliant one is how long ago somebody stood in it.
Further reading
PRC 4292: the ten-foot firebreak around a pole, and what counts: The cylinder, the three treatment layers by elevation, and which poles are subject poles.
Title 14 CCR sections 1250 to 1258: the implementing rules: The regulations that decide when and where the firebreak standard applies.
Documenting clearance work: What a unit record has to carry before somebody reads it back to you two years later.
Frequently asked questions
Does chamise have to be removed from a utility right-of-way?
Not from the right-of-way generally. It has to come out of the PRC 4292 firebreak around a subject pole. 14 CCR 1254(b) requires the removal of grass, herbaceous and brush vegetation from 0 to 8 feet above ground level inside the ten-foot cylinder, and chamise is brush vegetation whose documented mature height is 2 to 12 feet. Outside that cylinder, the rules that reach vegetation are measured from the conductor outward, and a shrub of that height standing on level ground under a span is rarely inside either one.
Will chamise grow into a distribution conductor?
The US Forest Service Fire Effects Information System puts the species at 2 to 12 feet tall, with growth almost negligible by 20 years after fire and 20-year-old postfire sprouts averaging 40.4 inches. Height alone does not close the gap to a conductor at ordinary framing height. The exposure comes from the ground it stands on rather than from the plant, which is why 14 CCR 1256 writes sway into the PRC 4293 clearance and names the location, height and species of the vegetation as inputs to it.
Why does cutting chamise not get rid of it?
Because the part that regrows the plant is below the cut. FEIS records that chamise sprouts vigorously from surviving adventitious buds on the lignotuber following disturbances such as fire or cutting, and that sprouts originate from a band of tissue 0.2 to 1 inch below the soil surface. A large plant can produce as many as 500 sprouts. A brush saw at ground level removes the crown and leaves the organ intact and undamaged.
What does chamise live fuel moisture have to do with a power line?
It is an input to operational decisions. San Diego Gas & Electric's amended post-event report for the January 7 to January 16, 2025 shutoff records that mid-December chamise measurements from the Cleveland National Forest's Palomar Ranger District read 61 percent for new growth and 57 percent for old growth, and that the average of the two is used as a data point in the Fire Potential Index calculation. The Fire Potential Index is one of four questions SDG&E states it asks before calling a Public Safety Power Shutoff.
When does the pole firebreak have to be clear?
PRC 4292 requires the firebreak during such times and in such areas as are determined to be necessary by the director or the agency with primary fire protection responsibility, and 14 CCR 1253 makes the firebreak provisions applicable during the declared CAL FIRE fire season for the respective county. Neither text sets a re-clear interval or a regrowth height that ends a clearing. The utility picks both, and CAL FIRE or the Commission grades the choice after an ignition.
