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Goldfields, Silt Slides, Oak Leaves, Invasive Thistle, Rough Trails, and a Reminder to be Watchful

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Goldfields blooming on Lasky Mesa - March 2024
Goldfields blooming on Lasky Mesa

Following are some notes and photos from runs in Upper Las Virgenes Canyon Open Space Preserve (Ahmanson Ranch) during March 2024.  Spring is here! The hills are green, goldfields and other wildflowers are blooming, and Las Virgenes Creek is flowing.

Goldfields and Other Wildflowers

The first goldfields (Lasthenia gracilis) of 2024 began to bloom on Lasky Mesa at the end of February. Now, bright yellow patches of these “belly” flowers are scattered across the mesa, adding a brush of color to the roads and trails of Ahmanson Ranch. The cheery flowers usually disappear with the first spell of hot and dry weather. Looking ahead, more rain and cool weather are forecast Easter weekend, and extended temperature outlooks are mixed. Hopefully, the goldfields will be around for a few more weeks.

Catalina mariposa lily at Ahmanson Ranch. March 27, 2024. (thumbnail)
Catalina mariposa lily. Click to enlarge.

Some other wildflowers are also blooming. Blue Dicks usually flourish following a wet Winter, but this March are less widespread than usual. Red maids are also less numerous than normal and their flowers somewhat smaller. The elegant white flowers of Catalina mariposa lily are just starting to bloom.

Thanks to T.S. Hilary’s false Spring and copious Winter rain, the hills of Ahmanson Ranch have been green since early October.

Silt Slides
Slides of silty soil in Upper Las Virgenes Canyon Open Space Preserve (thumbnail)
New (left) and old slides of silty soil. Click to enlarge.

With all the rain, small, shallow mudslides have been common along road cuts and other steep slopes of Ahmanson Ranch. The area has fine-grained silty soil. When saturated, it can generate a slurry of silt and debris. The numerous scars on the hillsides suggest this is a primary mechanism of erosion in the area.

Valley Oaks

After losing their leaves in December, the Valley Oaks at Ahmanson are now budding and sprouting. Some trees already have new leaves, while others are still bare-limbed. The period valley oaks are without leaves varies from year to year depending on rainfall, temperature, sunshine, and other factors.

Invasive Milk Thistle
Milk thistle in Las Virgenes Canyon
Milk thistle. Click to enlarge.

Milk thistle thrives during wet years, and it’s been very wet. We’ve had two consecutive wet years, plus a tropical storm thrown in for good measure. The invasive is sprouting in areas where it doesn’t normally grow and growing prolifically in areas where it is established. In a few months, milk thistle may look like it did in May 2005, following the record 2004-2005 rain year.

Rough Trails
Upper Las Virgenes Creek (thumbnail)
Upper Las Virgenes Creek. Click to enlarge.

Profuse rainfall is a two-edged sword. It revitalizes the ecosystem, turns the hills green, recharges the creeks, preserves the trees, produces wildflowers and more. But it can also be problematic — triggering slides, washing out and damaging trails, and promoting plant growth that chokes trails and increases the fire hazard.

At the moment, the roads and trails at Ahmanson are a bit rougher than normal, particularly in East Las Virgenes Canyon. Use and drier weather will gradually smooth out the ruts and rugosities, but we’re going to be picking foxtails from our socks for some time to come.

Upper Las Virgenes Creek is still flowing — including in the canyon’s upper reaches. Sometimes, there will even be a log or two in place to help keep your shoes dry.

And A Reminder to be Watchful
Baby rattlesnake at Ahmanson Ranch (thumbnail)
Baby rattlesnake. Click to enlarge.

I sometimes stretch at the info kiosk at the Victory trailhead before running. Today, as I placed my hands against one of the kiosk posts and started to stretch, I glanced down. Disturbingly close to my feet was a small snake. Adrenaline flowing, I checked the head and tail and then checked them again. I stepped back and began to breathe. It was a gopher snake. But it could have just as easily been a rattlesnake. In fact, later on that run, I encountered a baby rattlesnake. That day and the next (March 20 and 21), I saw a total of four gopher snakes and two Southern Pacific rattlesnakes.

Some related posts:

– Ahmanson Ranch  and Las Virgenes Creek After Six Days of Rain
– East Las Virgenes Canyon After a Seventh Day of Rain
– A Second Spring at Ahmanson Ranch
– Looking For Local Impacts of Tropical Storm Hilary

nature|insects, photography, photography|quirky, running|adventures, santa monica mountains

Apple Galls on Scrub Oak Along the Stunt High Trail

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Apple Galls on Scrub Oak Along the Stunt High Trail

The eye-catching colors of apple galls are like nothing else in chaparral and impossible to miss. These are on scrub oaks along the Stunt High Trail in the Santa Monica Mountains.

The galls are chemically induced by the larva of the California gall wasp, which uses the gall for food, protection, and to pupate. The rose color appears to result from exposure of the gall to sunlight.

I was descending the Stunt High Trail after visiting Saddle Peak while doing the Topanga Ridge Loop. As in other parts of the Santa Monica Mountains in which I’ve run following Hilary’s deluge, the trails were somewhat more eroded than usual but in OK shape.

Some related posts: Scrub Oak Apple Gall, Looking for Snow on Topanga Lookout and Saddle Peak, Topanga Lookout Loop, Plus Saddle Peak

ahmanson ranch, climate change, nature|trees, photography, trails, trees, upper las virgenes canyon open space preserve

Searching For Another Blue Oak In Upper Las Virgenes Canyon Open Space Preserve

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Blue oak-like leaves of an unusual oak in in Upper Las Virgenes Canyon Open Space Preserve (Ahmanson Ranch).

After the Ahmanson Blue Oak in East Las Virgenes Canyon died this Winter, I started to search for another blue oak (Quercus douglasii) in Upper Las Virgenes Canyon Open Space Preserve (aka Ahmanson Ranch). Blue oaks are rare at the southern limit of their range, but I was hopeful that if there was one blue oak at Ahmanson, there might be another.

Valley oak leaves in Upper Las Virgenes Canyon Open Space Preserve (Ahmanson Ranch).
Valley oak leaves.

Typically, blue oak leaves are noticeably different than valley oak leaves. The Jepson eFlora describes the leaf margins of blue oak as being more or less entire, wavy, or more or less lobed. The leaves of the Ahmanson Blue Oak fit this description. Valley oak leaves are usually much more deeply lobed and readily identified.

Recently, while on a run, I noticed an unusual oak near the top of a service road on the western margin of Lasky Mesa. Its leaves are not deeply-lobed and are a bit more dusky than the usual valley oak leaf. But the tree doesn’t look quite the same as the Ahmanson Blue Oak. One difference is that the shape of the leaves is not as uniform as those of the Ahmanson Blue Oak. This might be due to the wet 2022-2023 rain season and the flourish of leaves that resulted. And, as with the Ahmanson Blue Oak, this oak was burned in the 2018 Woolsey Fire, and its trunk is partially hollow.

Blue oak-like leaves of the unusual oak on the western margin of Lasky Mesa.
Blue oak-like leaves of an oak on the western margin of Lasky Mesa.

Based on its leaves, the “West Lasky Mesa Oak” could be a blue oak, blue oak hybrid, or valley oak hybrid. A 2002 study of a mixed stand of blue and valley oaks found that appearance can be misleading. When DNA tested, four of the five hybrid-appearing oaks in the study were not classified as hybrids. Of the four trees deemed most likely to be hybrids, only one oak was intermediate in appearance.

Although it seems unlikely this tree would have been overlooked, I could find no specific reference to the oak in the various studies and surveys done of Ahmanson Ranch. Please get in touch with me if you can provide additional information about this tree or how a DNA analysis can be arranged.

Some related posts: Ahmanson Blue Oak, Ahmanson Blue Oak Succumbs to Climate Change

ahmanson ranch, climate change, nature, nature|trees, photography, smmc open space, trails, trees, trees, upper las virgenes canyon open space preserve

Upper Las Virgenes Canyon Trailhead Valley Oak

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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

ahmanson ranch, nature|trees, nature|weather, photography, smmc open space, trails, upper las virgenes canyon open space preserve, weather|southern california

Ahmanson Valley Oaks Finally Get Their Leaves

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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 ranch, nature|trees, news, photography, smmc open space, trees, upper las virgenes canyon open space preserve, weather|southern california, wildfire

Ahmanson Blue Oak Succumbs to Climate Change

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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