Category Archives: nature|botany

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All in Which Family?

first published March 25, 2008 & last updated April 25, 2018 Gary Valle

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Indian warrior (Pedicularis densiflora) on the Backbone Trail in the Santa Monica Mountains.

Indian warrior’s varying tones of carmine contrast sharply with its lush green leaves and create a striking combination of colors when seen along a trail. Surprisingly, it is the green of its leaves that is one of its interesting features.

Indian warrior (Pedicularis densiflora) resembles two other wildflowers you might see along a Southern California trail — Indian paintbrush (Castilleja affinis) and Owl’s clover (Castilleja exserta). All three are related root parasites that obtain water and nutrients from their host, but also contain chlorophyll and can photosynthesize carbohydrates.

It seems this characteristic would be of value in a climate where seasonal rainfall is highly variable, extending the parasitic plant’s access to water.

Recent genetic analysis has revealed that Pedicularis and Castilleja are related to plants in the Broomrape family (Orobanchaceae), rather than those in the Figwort family (Scrophulariaceae), in which they have been classified. This was a somewhat unexpected result because one of the distinguishing characteristics of Orobanchaceae had been the lack of chlorophyll.

The photograph was taken on the Backbone Trail on the run described in A Long Run Kind of Day.

Technical References:

The Physiology of Plants Under Stress By Erik T. Nilsen, David M. Orcutt

PLANTS THAT LIKE HOSTS By Toni Corelli

Phylogeny of the parasitic plant family Orobanchaceae inferred from phytochrome A[1]

Jonathan R. Bennett and Sarah Mathews

Google search: $g(parasites), $g(Orobanchaceae), $g(chlorophyll), $g(phylogeny), $g(genetics)

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Tracking the Sun

first published March 2, 2008 & last updated October 5, 2023 Gary Valle

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Mallow leaves tracking the sun.

Updated 03/13/08.

My run of the “keyhole loop” at Ahmanson Ranch started out as a tempo run — not so much as being part of a rigorous training program, but because of a dead battery in my car remote. It felt good to push the pace a bit.

Part way through the loop, running up a short hill into the sun, I was struck by a repetitive pattern of backlit leaves in the new growth on and alongside the road. Like little green satellite dishes, hundreds of the round leaves of mallow were facing directly into the late afternoon sun.

Mallow (Malva spp.) is an invasive plant from the Mediterranean area that has flourished in Southern California’s Mediterranean climate. In most years, it is very common. I’ve run and hiked past thousands of these plants, but never noticed this synchronicity.

Tracking the sun makes sense. Our climate has an extremely variable and relatively short growing season. A plant that maximizes its intake of solar energy and growth by orienting its leaves toward the sun would have an advantage over a less adaptable species. This is probably one of the reasons mallow is such a successful invasive. Another invasive that grows alongside mallow, black mustard, also appears to exhibit heliotropism as it is growing. It creates a rosette of leaves facing into the sun by raising leaves on the side of the stalk away from the sun, and lowering leaves on the side of the stalk toward the sun.

From a run during the week at Ahmanson Ranch — now Upper Las Virgenes Canyon Open Space Preserve.

Technical papers:

Diaphototropic Movement of the Leaves of Malva Neglecta

H. C. Yin
American Journal of Botany, Vol. 25, No. 1 (Jan., 1938), pp. 1-6

HELIOTROPISM AND WATER AVAILABILITY EFFECTS ON FLOWERING DYNAMICS AND SEED PRODUCTION IN Macroptilium lathyroides

ARMANDO MARTINS DOS SANTOS, LUIS MAURO GONÇALVES ROSA, LUCIA BRANDÃO FRANKE, CARLOS NABINGER

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Santa Susana Tarweed

first published October 16, 2007 & last updated June 22, 2023 Gary Valle

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Santa Susana tarweed (Deinandra minthornii)

Listed by the California Native Plant Society as being rare, threatened, or endangered, Santa Susana tarweed (Deinandra minthornii) can be found where sandstone outcrops of the Chatsworth formation occur, such as in the Santa Susana Pass area in the Simi Hills.

This photograph was taken on a run at Sage Ranch on October 1, 2007.

Note: Treated as Hemizonia minthornii in the 1993 Jepson Manual.

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Tumbleweed Blossom

published October 12, 2007 Gary Valle

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Blossom of tumbleweed (Salsola tragus)

Maybe it’s the result of record low rainfall, or the 2005 Topanga Fire, or a combination of the two — there has been a dramatic increase in the amount of tumbleweed (Salsola tragus) along the dirt roads in Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch).

Like black mustard, and milk thistle, tumbleweed is an invasive plant. According to UC IPM Online tumbleweed is native to southeastern Russia and western Siberia and was first introduced into the United States (South Dakota) in 1873.

The photograph of the tumbleweed flower was taken on a run at Ahmanson Ranch on October 3, 2007.

Some related posts: Dealing With Drought, Milk Thistle Seed Heads, Curly Dock

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Leaf Vein Networks

first published August 10, 2007 & last updated July 6, 2022 Gary Valle

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Study of a leaf of a Fremont cottonwood (Populus fremontii) along Las Virgenes Creek in Upper Las Virgenes Canyon Open Space Preserve.

Who hasn’t pondered the intriguing network formed by the interconnected veins of a leaf? Like many apparently complex self-organized structures, there is a recognizable pattern, but the basis of the pattern is difficult to grasp.

Remarkably, research published in 2002 (S. Bohn et al., Phys. Rev. E, June 2002.) found that there is a simple relationship governing the angles between vein segments in the leaves of dicotyledons, and that this relationship is universal. The study also found that the observed vein angles can be reproduced using a simple force model.

Numerical analysis of leaf scans revealed that the angles between vein segments are directly related to the thickness of the segments. When the vein sizes are similar, the connection appears to form a three-way junction with the angle between the veins about 120 degrees. If the vein sizes are dissimilar, with one much larger than the other, the smaller vein joins the larger at about a 90 degree angle.

The photograph is of a leaf of a Fremont cottonwood (Populus fremontii) along Las Virgenes Creek in Upper Las Virgenes Canyon Open Space Preserve. It was taken on a run from the Victory trailhead on May 16, 2007.