Category Archives: nature|botany

nature, nature|botany, photography

Tracking the Sun

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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

nature, nature|botany, nature|wildflowers, photography, photography|wildflowers

Santa Susana Tarweed

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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.

nature, nature|botany, nature|wildflowers, photography

Tumbleweed Blossom

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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

green, nature, nature|botany, nature|trees, photography, photography|still life

Leaf Vein Networks

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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.

nature, nature|botany, nature|insects, nature|wildflowers, photography, photography|insects, photography|wildflowers

Mountain Mariposa

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Mariposa lilies (Calochortus invenustus) blooming through the palmate leaves of a lupine at about 8500 ft., near Sawmill Mountain, west of Mt. Pinos.

Mariposa lilies (Calochortus invenustus) blooming through the palmate leaves of a lupine at about 8500 ft., near Sawmill Mountain, west of Mt. Pinos.

According to data from the Consortium of California Herbaria, this species was documented in the Mt. Pinos area as early as 1897.

The wasp-like insect is a hover fly, probably Chrysotoxum festivum.

From Sunday’s Mt. Pinos-Mt. Abel Out & Back run.

Related posts: Plummer’s Mariposa Lily, Bee Fly On Western Wallflower

nature, nature|botany, nature|wildflowers, photography, photography|wildflowers

Gumplant

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Gumplant (Grindelia hirsutula var. hirsutula) in Upper Las Virgenes Canyon Open Space Preserve

In a Spring in which there has been little rain and a reduced number of wildflowers, the vibrant yellow of gumplant has been a welcome sight along Ahmanson’s main trail in Upper Las Virgenes Canyon Open Space Preserve near the Victory trailhead.

This appears to be Grindelia hirsutula var. hirsutula, a species considered rare in Ventura County. It is reported that a species of gumplant was used medicinally by the Chumash, and other native peoples within its range, for treatment of pulmonary problems.