Category Archives: ahmanson ranch

Upper Las Virgenes Canyon Trailhead Valley Oak

Large valley oak near the Upper Las Virgenes Canyon Trailhead of Upper Las Virgenes Canyon Open Space Preserve (aka Ahmanson Ranch)

This large valley oak lives near the Upper Las Virgenes Canyon Trailhead of Upper Las Virgenes Canyon Open Space Preserve (aka Ahmanson Ranch). There used to be several large valley oaks near the trailhead, but they were killed in the 2018 Woolsey Fire.

The trunk of the Upper Las Virgenes Canyon Trailhead valley oak.
The brim of the cap is about 7 inches wide.

This tree is as large as any of the valley oaks I see along the trails at Ahmanson. I estimate it’s diameter to be a little under four feet. That’s not large by Northern California standards, but it is still a sizable tree. Valley oaks have a tougher time here.

Along with coast live oak, the valley oak is one of the iconic species of oak-grasslands at Ahmanson Ranch. In the past 20 years, valley oaks at Ahmanson Ranch have been more severely impacted by drought, fire, and rising temperatures than live oaks. In the not too distant future, the valley oak may become a relic at Ahmanson, much like the blue oak that died earlier this year.

Some related posts: Ahmanson Valley Oaks Finally Get Their Leaves, Ahmanson Valley Oaks Battling Drought, Ahmanson Blue Oak Succumbs to Climate Change, and Many More

Lasky Mesa Runner, Grassland, and Clouds

Lasky Mesa Runner, Grassland, and Clouds

Brett was down for a few days, and as an initial run we did a loop from the Victory Trailhead of Ahmanson Ranch, through part of Las Virgenes Canyon, up onto Lasky Mesa, and then back to the trailhead.

Upper Las Virgenes Creek still flowed. Valley oaks were full with new leaves. The green grasses of the rain season had finally turned, and rare May cumulus clouds were painted on postcard skies.

It was an outstanding run!

Ahmanson Valley Oaks Finally Get Their Leaves

Cold weather delayed the leafing out of valley oaks at Ahmanson ranch until late March and early April 2023.

According to preliminary NWS reports, Downtown Los Angeles (USC) recorded average monthly temperatures well below normal in November 2022 and January thru March 2023. March was particularly cool, with an average high of about 64 degrees and an average low of about 50 degrees.

Besides high heating bills, Southern California’s unusually cold Winter affected several seasonal processes, one of which was when the valley oaks at Ahmanson budded and grew new leaves.

The leaves of valley oaks at Ahmanson Ranch typically turn in mid-December, and the trees usually begin to leaf out during the latter half of February. Depending on the tree’s microclimate, the emergence of new leaves may vary by a week or more.

Cooler than normal temperatures during January to March 2023 delayed the leafing out of these valley oaks in Las Virgenes Canyon.
Valley oaks in Las Virgenes Canyon in early April 2023.

The earliest I’ve photographed a valley oak at Ahmanson sprouting new leaves was February 3, 2015. Last year, a valley oak had new leaves on February 10, 2022.

The latest I’ve seen valley oaks sprouting new leaves is this year — from about March 20, 2023, in favored locations to April 4, 2023, in cooler areas such as Las Virgenes Canyon.

Prior to this year, the latest I’ve photographed a valley oak at Ahmanson with new leaves was March 9, 2009.

(Officially named Upper Las Virgenes Canyon Open Space Preserve, most users refer to the open space area as Ahmanson Ranch or simply Ahmanson.)

Some related posts: Revitalized Valley Oak at Ahmanson Ranch, Goldfields Are Blooming and Valley Oaks Greening, Valley Oak Leaf

Ahmanson Blue Oak Succumbs to Climate Change

Rare at this latitude, this blue oak at Upper Las Virgenes Canyon Open Space preserve succumbed to drought, fire, and above average temperatures.

When I rounded the corner on the Lasky Mesa Trail, I could hardly believe my eyes. The Ahmanson Blue Oak was gone. Where there had been a sprawling oak, there was nothing.

Crossing an eroded section of trail and walking over to the edge of the old roadbed, I looked down the slope. Much like this valley oak along Rocky Peak Road, the entire Ahmanson blue oak  had fallen from its hillside perch near the bottom of the canyon.

Oaks in the oak-grasslands of Upper Las Virgenes Canyon Open Space Preserve have had a tough time with climate change. The five-year drought from July 2011 to October 2016, increasing temperature, and the 2018 Woolsey Fire have combined to kill a large number of trees.

This blue oak was one of very few found at the southern extent of its range.

Related posts: Ahmanson Blue Oak, Ahmanson Valley Oaks Battling Drought, After the Woolsey Fire: Ahmanson Ranch, Fallen Oak, Valley Oak Savanna

Snow-Covered San Gabriel Mountains From Lasky Mesa

Snow-covered San Gabriel Mountains from Lasky Mesa in Upper Las Virgenes Canyon Open Space Preserve (Ahmanson Ranch)

It had rained another inch overnight, and my shoes were soaked from the wet grass along the trail. Seeking some relief from the 20 mph northwest wind, I descended a single-track trail to an old paved road east of the ranch house on Lasky Mesa.

Motivated more by staying out of the wind than anything else, I did two sets of hill repeats on different sections of the road. Then, on tired legs, I jogged up to Lasky Mesa and was greeted by an Arctic blast. The temperature had dropped to the mid-40s, and the wind was blowing a steady 20 mph, gusting to around 30 mph. I didn’t need a wind chill chart to tell me the effective temperature was in the 30s.

I was so focused on dealing with the cold I wasn’t paying much attention to my surroundings. Deciding to do one more hill, I rounded a corner, and the brilliantly sunlit, snow-covered San Gabriel Mountains came into full view. It was just jaw-dropping!

Here is a wider view of most of the Front Range of the San Gabriels, white with snow.

Some related posts: Chasing Rainbows at Ahmanson Ranch, Looking for Snow on Topanga Lookout and Saddle Peak