Los Peñasquitos Canyon Is Open Again. The Yellow Rope Is How It Stays That Way

"In other agencies, fire closures last years. Ours is partial and will be counted in weeks." City of San Diego Park Ranger Melanie Fontana wrote that on Sept. 13, when the whole west end of Los Peñasquitos Canyon Preserve was still closed. Nineteen days later, on Oct. 2, Senior Park Ranger Gina Washington announced that all authorized trails in the preserve were open again.

Rangers paid for that quick reopening with yellow rope. Several thousand feet of temporary fencing now runs along the North and South Main Trails through the burn scar. In the rangers' own description, the fencing is temporary "on an ecological timescale." That means it stays until the habitat grows back, which could take "anywhere from months to years." Getting the canyon back this fast came with a condition, and the rope is it.

Two Fires, One Long Summer in the West End

The canyon burned twice this year, and the second fire moved through ground the first one had already burned.

Rangers put the combined burn scar at "over 230 acres." It crosses several miles of authorized trail, including the North Main, South Main, Sidehill, and Big and Little Waimea trails. Those are the main routes through the west end of the canyon toward Sorrento Valley. Most of them reopened as a single package on Oct. 2.

Why the Closure Lasted Into September

The flames were out long before the trails opened. In the first week after the emergency response, embers kept reigniting in hot spots. After that, the problem was trees.

According to Fontana's bulletin, many adult trees along the trails were girdled by the fire and many young trees burned completely. Fire burns out the dead heartwood, and the heat boils the sap in what was still living wood. That weakens the tree "catastrophically" and makes it likely to drop limbs or fall over. As of Sept. 13, San Diego Fire-Rescue was working with park staff to assess and triage the dangerous trees, and the plan was to start cutting that week. Because tree work is a secondary duty for firefighters, the bulletin said crews would fit it in between engine and paramedic calls.

Fire crews are still working in the canyon after the reopening. Washington's Oct. 2 notice says there will be "periodic trail closures" while San Diego Fire-Rescue crews work on the access roads. The closures will be temporary and targeted. The City lists the Park Ranger Office at 858-538-8066 for current trail status, so a call before a long out-and-back can save you a wasted trip.

What the Rope Is Protecting

Most of the rangers' explanation is about soil.

"Human activity in the burn scars hampers regrowth of vegetation. It destroys the fragile ashy crust formed during the fire and the molecular soil bonds that protect the soil from the erosive power of wind and rain."

Once that crust breaks, soil and ash turn to dust that wind and water can carry away. The risk is higher on slopes, and the damage reaches habitat downstream as well as the burn scar. Fontana's bulletin raises the concern further "in the face of the increased rain predictions associated with El Niño years." A shortcut through burned ground in October can mean a gully on the slope by spring.

The second concern is seeds. Shoes, tires, and paws carry nonnative seeds into burned areas. Rangers say that can turn a native plant community into one dominated by invasive species. They call that kind of habitat conversion the biggest threat to the region's biodiversity, because nonnative vegetation supports only a fraction of the wildlife that native vegetation does. Many native species are adapted to resprout from seed and surviving roots after a fire. The fencing gives them room to do that.

The rope also helps with route-finding, which is a real issue right now. The ranger bulletin says many of the plant-based landmarks are gone, and emergency equipment and crews left tracks that make the actual trail hard to pick out. If you've walked the South Main Trail for years and know it by the bushes, those cues are gone. Follow the rope.

The First Weekend Back Comes With a Heat Warning

The trails reopened just as an extreme heat warning took effect for this weekend. Washington's notice asks visitors to bring plenty of water, avoid peak afternoon heat, and know their limits. It also says dogs can overheat very easily and suggests leaving them home. The same notice reports more animal activity throughout the west end of the canyon since the fire.

Where to Start a Hike This Fall

Your trailhead depends on how much of the burn scar you want to see.

• Park Village Road trailhead. The City calls the end of Park Village Road the shortest, easiest route to the Waterfall. It's 1.3 miles, or about 20 to 30 minutes, along the North Main Trail.
• West staging area. This lot is on the south side of Sorrento Valley Boulevard, about a mile east of Vista Sorrento Parkway. It puts you at the western end, where both fires burned.
• East staging area at Black Mountain and Mercy Roads. The County lot at 12020 Black Mountain Road is open daily from 8 a.m. to sunset for vehicle and equestrian parking. County day-use parking is listed at $5 per day.
• Other entrances. The northern entrance is near Peñasquitos Creek Park at Park Village Road and Camino Del Sur. The southern entrance is at the Camino Ruiz neighborhood park, on the Mira Mesa side. The Lopez Canyon staging area is at Pacific Mesa and Pacific Center Boulevards.

The Waterfall is now the dividing line between the part of the canyon that never closed and the part that did. Starting at Park Village Road gets you there quickly. From there, every step west is through the area the rangers fenced.

Helping the Canyon Recover This Fall

Several groups that care for the preserve have events on the calendar through November. None of them is listed as fire-scar or fencing work.

Waterfall Rehabilitation Project, Oct. 10 and Nov. 14, 9 a.m. to noon. On the second Saturday of each month, Ranger Haley and Senior Ranger Gina meet volunteers at a habitat restoration site at the Waterfall on the North Main Trail. The City describes it as a native prairie and pollinator site. Volunteers water plants, remove invasive species, and expand the site a little at a time. It's the same kind of native-plant work the burn scar now needs, just a few steps from the fencing.

Restoration in Black Mountain Open Space Park, Sunday, Oct. 4, 4:30 to 6:30 p.m. Friends of Los Peñasquitos Canyon Preserve meets at Black Mountain Ranch Community Park to plant, weed, and water habitat for endangered birds and butterflies. No experience or individual RSVP is required.

Ranch House tour, Sunday, Oct. 4, 1 p.m. County Parks lists a docent-led tour of the Los Peñasquitos Ranch House, which it describes as 200 years old.

Arch in the Park, Saturday, Oct. 17, 10 a.m. to 3 p.m. The San Diego County Archaeological Society hosts this California Archaeology Month event at Canyonside Park. Friends of Los Peñasquitos will have a booth there.

Friends of Los Peñasquitos also planted six large Channel Island oaks, mostly 60-inch-box trees, earlier this year in the canyon parking area just east of the community gardens.

How Long the Rope Stays

There's no removal date. The fencing comes down only when the habitat has "suitably grown-in," and the ranger bulletin says how long that takes depends on the type of habitat. The bulletin's range runs from months to years.

Fontana's bulletin ties the outcome to how people use the trails. "With your cooperation and that of your friends, family, and associates with whom you might share this information, our canyon could end up healthier and more resilient for this disturbance, with renewed vitality and increased biodiversity." Staying on the trail inside the rope through this winter's rain gives native plants the best chance to grow back.

For more on the trails, parks, and streets around the preserve, see our Rancho Peñasquitos neighborhood guide. The canyon also borders Mira Mesa, whose Camino Ruiz entrance is listed above.

A canyon that starts at the end of the street is part of daily life for many Rancho Peñasquitos homeowners. When it's time to plan a sale or a move, Jim Bottrell Team brings the same local knowledge and disciplined preparation to the decision. Start with a Free Home Valuation and see where your home stands this fall.