Sunday, September 27, 2009

Leadwort

What’s blooming in the area: Tamarix, tea roses, Apache plume, butterfly bush almost gone, trumpet creeper, Japanese honeysuckle, silver lace vine, leather leaved globemallow, alfalfa, white sweet and white prairie clovers, yellow evening primroses, datura, goats’ head, bouncing Bess, stickleaf, chamisa, winterfat, ragweed, snakeweed, native and farmer’s sunflowers, áñil del muerto, horseweed, wild lettuce, African marigolds, tahokia daisies, purple, heath, strap-leaf and hairy golden asters, pampas grass; canna buds, bittersweet berries; more Virginia creeper turning red.

What’s blooming in my yard, looking north: Zucchini, nasturtium, Mexican hat, chocolate flower, blanket flower, black-eyed Susan, chrysanthemum; leaves on butterfly weed turning yellow, catalpa leaves turning yellow and dropping, sand cherries turning red, seeds on blackberry lily.

Looking east: California poppy, hollyhock, winecup, snapdragons, Jupiter’s beard, large-leaved soapwort, Autumn Joy sedum, garlic chive, Maximilian sunflower; leaves on peony turning color.

Looking south: Rose of Sharon, sweet pea, Crimson Rambler morning glories, zinnia, cosmos; grapes turning red.

Looking west: Caryopteris, Russian sage, catmint, calamintha, David phlox, leadwort, purple ice plant, Silver King artemisia, purple coneflower, Mönch aster; leaves turning orange on skunkbush and white spurge; peach leaves turning yellow and dropping.

Bedding plants: Moss rose, sweet alyssum; edible tomatoes.

Inside: South African aptenia.

Animal sightings: Rabbit, geckos, bees, wasps, grasshoppers, large black harvester and small dark ants.

Weather: Short bursts of strong winds late some days; rain Thursday; 11:55 hours of daylight today.

Weekly update: Some flowers are definitely camera shy. Some weigh so little, they never stay still long enough for a camera to capture them. Others reflect so much light they blind the lens. The blues are trickiest of all, because their wiles defeat the camera itself, not just the photographer.

Of all the blue flowers in my garden, leadwort is the hardest to photograph. Early in the morning, when the Chinese natives are in shade, images look like they were taken underwater. By the time the sun reaches the west facing bed, the petals have begun to protect themselves by reflecting light. I was only able to get a clear picture last Sunday when the sky was still bright, but a little rain was falling. Even then the color was wrong.

Unlike the old silver-based film cameras, nothing is constant with a digital device. Then, if a picture was out of focus, the photographer knew he or she hadn’t set the distance parameter, the focal length, properly. With a computer-controlled camera, two parts of a plant the same distance from the lens, will appear in different degrees of detail. The reddish brackets that hold the pinkish tubes of the five-petaled leadwort flowers are always clear.

The same variation occurs with color. When the light is right, the leaves, the stems, the tubes and brackets are reasonably true, but not the petals. The reds, greens, browns and whites are fine. Only the blues are bad.

The chemicals in the plant absorb light both as part of photosynthesis and as the nature of matter. What we see is the light that’s not absorbed. In the case of leadwort, the flower is absorbing the yellow center of the visible light spectrum and ignoring the reds and blues, which the human eye combines into purple. On the other hand, the leaves are rejecting the green, and using the rest of the light to feed themselves

Jeffrey Harborne identified the flower pigment in Ceratostigma plumbaginoides as europinidin, a reddish blue anthocyanin derivative of the bluish purple delphinidin typically found in members of the plumbago family. Later this fall, when the leaves turn a burgundy red, the plant will have produced a cyandin monoside that will reflect light differently. Earlier, when they broke through the ground the second week of May, the new leaves were a shiny green.

Chemists themselves have troubles defining colors precisely. When William Lawrence’s team was testing the anthocyanin pigments in fall leaves, they found a number had one hue when seen in daylight and another when seen in artificial light. The nature of light is not constant from morning to noon, from clear to cloudy, from June to September.

Whenever I try to explain to myself what has happened with my pictures I get tangled in the differences between the reality of the physicist’s linear spectrum that fades into infrared at one end and to ultraviolet at the other, and the vocabulary of the artist’s color wheel which sees purple as the junction between red and blue. When I compare the photograph with the flower I see, it looks like the blue is bad because the red has been lost, only the blue has become lighter, not darker as a consequence.

I finally defined the two colors, the actual flower and its representation in the language of the computer monitor, which sees everything as a mix of red, green, and blue. The one is roughly 130 parts red to 50 parts green to 255 parts blue. The other is 100 parts red to 130 parts green to 245 parts blue. The first formula lacks the depth of the petals, but 255 is the maximum allowed for any color. The second doesn’t capture the sheen or white overtones of the photograph.

My camera uses the established technology that existed when it has introduced in 2005. The light enters through the lens to bounce against a prism that redirects it down to the CCD chip that converts the light into electronic impulses. Thom Hogan indicates such chips are more attuned to the high-energy infrared and somewhat blind to the low-energy blues. Some of the loss of blue, from 255 to 245, may be a consequence of that limitation; some of the loss of red (from 130 to 100) may come from the manufacturer’s attempt to compensate for the infrared sensitivity.

Computer chips only see on and off, which translate into black and white monochromes. The first stage of coloration comes from two layers of filters that sit above the CCD chip. One alternates red and green filters, the other blue and green so every point on the chip has one green filter and one of another color. At this point, the only loss of color comes from the quality of the filters.

The camera then takes the information from the chip and from the filters and combines them, using proprietary algorithms that try to reconstruct the relative importance of the data captured by the two layers. Since engineers know most people are more sensitive to green, than to red or blue, they tend to favor green when the pattern isn’t clear. And so, the amount of green in my picture is increased from 50 to 130, which distorts the flower color.

The variations increase when the image is transferred to a computer monitor or printer, because each piece of equipment has its own way of translating the RGB schema.

I originally asked questions about my camera’s technology so I would have some idea what features I needed if I replaced it. It never occurred to me to alter my garden so only the flowers that could be photographed would be allowed to grow. Nature is still more complex that it’s scientific representation, and flowers can be remembered without mechanical devices.

Leadwort is one of the last perennials to emerge in spring, rising in new places along the soaker hose where its rhizomatous roots have extended themselves. It’ll be one of the more colorful this fall. It’s now been putting out low flowers every few days since the middle of August. I grow it for the pleasures lived and those remembered, not for being recordable.

Notes: Charge-coupled devices (CCD’s) were developed in 1969 by Willard Boyle and George E. Smith at AT&T Bell Labs. The network of filters was patented by Bruce Bayer for Kodak in 1976. In the nineteenth century, Thomas Young and Hermann von Helmholtz established humans perceived colors from only three band widths of light; the existence of separate human receptors for red, green and blue (RGB) was finally established in 1983 by Herbert James Ambrose Dartnall, James K. Bowmaker, and John D. Mollon. What I call a part of color, using the language of artists, actually refers to the intensity of the light measured by the physicist.
Hogan, Thom. "How Digital Cameras Work," bythom website, last revised 9 April 2009, provides the clearest explanation for the layman.
Harborne, J. B. "Comparative Biochemistry of the Flavonoids-IV: Correlations Between Chemistry, Pollen Morphology and Systematics in the Family Plumbaginaceae, " Phytochemistry 6:1415-1428:1967.
Lawrence, William John Cooper, James Robert Price, Gertrude Maud Robinson, and Robert Robinson. "A Survey of Anthocyanins. V," Biochemistry 32:1661-1667:1938.
Photograph: Leadwort, taken around 3:30 on 20 September 2009.

Sunday, September 20, 2009

Heath Aster

What’s blooming in the area: Tamarix, tea roses, Apache plume, butterfly bush, trumpet creeper, Japanese honeysuckle, silver lace vine, leather leaved globemallow, alfalfa, white sweet clovers, white and yellow evening primroses, datura, Heavenly Blue and ivy-leaf morning glory, scarlet creeper, bindweed, goats’ head, bouncing Bess, pale trumpet, stickleaf, clammy weed, spurge, pigweed, Russian thistle, winterfat, ragweed, snakeweed, native and farmer’s sunflowers, áñil del muerto, Hopi tea, horseweed, wild lettuce, purple, heath, strap-leaf and hairy golden asters, goldenrod, tahokia daisy; bittersweet berries, apples falling.

What’s blooming in my yard, looking north: Zucchini, nasturtium, Mexican hat almost gone, chocolate flower, blanket flower, black-eyed Susan almost gone, chrysanthemum.

Looking east: California poppy, hollyhock almost gone, winecup, snapdragons, Jupiter’s beard, large-leaved soapwort, Autumn Joy sedum darkening, garlic chive, Maximilian sunflower.

Looking south: Blaze roses, rose of Sharon, sweet pea, Crimson Rambler and reseeded morning glories, zinnia, cosmos.

Looking west: Caryopteris, Russian sage, catmint, calamintha, flax, sea lavender, David phlox, leadwort, perennial four o’clock, purple ice plant, Silver King artemisia, purple coneflower, Mönch aster.

Bedding plants: Moss rose, sweet alyssum.

Inside: South African aptenia.

Animal sightings: Rabbit, hummingbird, geckos, bees, wasps, grasshoppers, large black harvester ants, explosion of small dark ants

Weather: Rain Wednesday and Thursday; mornings were cold enough for the furnace to come on and my neighbor to fire up his chain saw to cut fire wood; 12:15 hours of daylight today.

Weekly update: Mornings turn cold, heath asters open, and my thoughts turn to Billy Grammer. In 1959 he sang "summer’s almost gone, winter’s coming on."

Grammer’s answer was it’s time to travel on. That’s good advice for hummingbirds raiding the last hollyhocks, but what about the bees and wasps and other insects still flitting about?

My bees probably come from some hive maintained down by the orchards, and will survive the winter by clustering together and beating their wings to produce enough heat to keep themselves warm. The six-legged creatures only venture out when temperatures rise above 50, so will subsist on stored honey.

Other bee species and wasps have no such surplus. The social wasps, and hornets that are part of that insect group, spent the summer feeding larvae with animal proteins from insects they had killed, including ones that would have eaten the leaves or sucked the juices from my wild asters. The adults themselves lived on sugars and got some nutrients from the process of feeding the grubs, some from flowers, and some from foraging in garbage.

Now the larvae are grown and everyone needs to eat. In some species, the young females will impregnate themselves and burrow under leaves or find an attic to hibernate for the winter. Others will simply lay eggs which remain dormant until spring. The rest, the workers, will die.

Unfortunately, they all need food just when most flowering plants are responding to nature’s signals that winter’s coming on by moving to seed production. Wasps don’t have the specialized tongues of bees and need open, shallow autumn flowers where nectar is easily available. They must have had a tough time this past week when the white asters pulled up their twelve ray flowers to shed the rain.

The small, white composites, like many related asters, seem to have two growth cycles related to changes in light. The basal rosettes emerged this year in late April, but the tall plumes of narrow green leaves didn’t appear until late July, nearly six weeks after the long days of mid-summer stimulated their production. It wasn’t until the shorter days of fall that the flower clusters were ready to open.

With so little time to produce seed and visitations by smooth wasps, who aren’t as efficient at pollinating as hairy bees, heath asters have found others way to perpetuate themselves. Every spring I remember how the skinny stalks turn into a hedge that overshadows everything before smothering the lower plants when they collapse. I pull out most of the plants, but strands of their stolonous roots break off.

After the heat of summer drives me inside, the perennials spread underground and push up new shoots back near the water and paths. By then, it’s too late to do anything except plan how to control them the next year.

Man has found little use for Aster ericoides. Some call it steel weed because the woody brown stems dull their tools; others call it good-bye meadow because it’s poor forage. Only the Meskwaki used it to their lash together their sweat lodges and tested its herbal uses.

The seeds, if they get produced, can last several years. Heath asters are one of the first things to return in tall grass prairies when fields are abandoned. They dominate the land for a few years, then succumb to competition from other plants, including the grasses. When they bloom, they stretch from Manitoba to northern Mexico and provide a nectar path for migrating monarch butterflies, as well as a steady diet for the more sedentary silvery checkerspots.

These are precious weeks when life is suspended between summer and winter. Heath asters may attract stinging insects, but they have no inhibitions about blooming until frost. We can’t all travel on. Those of us who stay around, deserve our pleasures too.

Notes:Clayton, Paul. "Gotta Travel On;" Bob Colton discusses the origins of the song in Paul Clayton and the Folksong Revival, 2008.

Hilty, John. "Heath Aster," Illinois Wildflowers website has more details on insects.

Smith, Huron H. "Ethnobotany of the Meskwaki Indians," Public Museum of the City of Milwaukee Bulletin 4:175-326:1928, cited by Dan Moerman, Native American Ethnobotany, 1998.

Photograph: Heath aster with wasp on cloudy day, 16 September 2009; brown sweet pea pods in back.

Sunday, September 13, 2009

Autumn Joy Sedum

What’s blooming in the area: Tamarix, tea roses, Apache plume, trumpet creeper, Japanese honeysuckle, silver lace vine, leather leaved globemallow, alfalfa, white sweet and white prairie clovers, velvetweed, scarlet beeblossom, white and yellow evening primroses, datura, Heavenly Blue and ivy-leaf morning glory, scarlet creeper, bindweed, goats’ head, purple phlox, bouncing Bess, pale trumpet, stickleaf, clammy weed, spurge, pigweed, Russian thistle, winterfat, ragweed, snakeweed, native and farmer’s sunflowers, áñil del muerto, Hopi tea, horseweed, wild lettuce, purple, heath, strap-leaf and hairy golden aster, goldenrod, tahokia daisy, pampas grass; tiny apricots and apples coming down; red peppers and ripe watermelon.

What’s blooming in my yard, looking north: Zucchini, nasturtium, Mexican hat, chocolate flower, blanket flower, black-eyed Susan, chrysanthemum.

Looking east: Hosta, California and Shirley poppies, hollyhock, winecup, sidalcea, snapdragons, Maltese Cross, Jupiter’s beard, large-leaved soapwort, Autumn Joy sedum, garlic chive, Maximilian sunflower.

Looking south: Blaze roses, rose of Sharon, sweet pea, Crimson Rambler and reseeded morning glories, zinnia, cosmos.

Looking west: Caryopteris, butterfly bush, Russian sage, catmint, calamintha, lady bells, flax, sea lavender, David phlox, leadplant, perennial four o’clock, purple ice plant, Silver King artemisia, purple coneflower, Mönch aster; peaches falling.

Bedding plants: Moss rose, sweet alyssum.

Inside: South African aptenia.

Animal sightings: Rabbit, geckos, bees, large black harvester and small dark ants, grasshoppers.

Weather: Rain in area all week, but all I got was late afternoon clouds; last night not enough water fell to dampen the surface; last real rain 8/30/09; 13:45 hours of daylight today.

Weekly update: My Autumn Joy sedum is now at the stage where the rose red, five-petaled flowers attract bees.

The three plants formed new basal rosettes of pale, scalloped leaves in early March. The single, stout stems emerged in early July. The fattening buds, held in flat clusters like yarrow, showed streaks of white when the protective sepals were forced apart later in the month. Two weeks ago the florets started to open a pale pink, and now the tips are darkening.

The perennial’s not only one of the more colorful fall flowers, but also a sign of nature's ability to survive the worst that the climate or man can contrive.

In 1863, the ambitious son of a silk worker, Friedrich Bayer, and master dyer Johann Friedrich Weskott opened a factory in Barmen to produce synthetic dyes from coal tars. Eight years after Bayer died, Georg Arends opened a nursery in Ronsdorf on the same Rhine tributary in 1888.

Chemists were then improving upon nature by taking known, discrete elements and mixing them to see what would result. Ten years before Bayer changed from selling dyes to manufacturing them, Charles Frederic Gerhardt combined acetyl chloride with a sodium salt of salicylic acid to produce a synthetic form of the white willow bark then used to treat fever and inflammation. In 1897, a Bayer chemist, Felix Hoffmann, found a way to produce acetylsalicylic acid in a stable form that could be mass produced as aspirin.

Breeders were applying the same methods to nature. In the early 1900's, Arends began introducing new varieties of astilbe that crossed at least four species. In the 1920's, he was experimenting with sempervivums, another succulent in Autumn Joy's Crassula family. And in 1939, the same year Hitler invaded Poland, he introduced a new hybrid heath, Silberschmelze.

In the same years, Bayer was assimilated into I.G. Farbenindustrie, and the towns of Barmen, Ronsdorf and Elberfeld, where Bayer had moved its operations, were merged into Wuppertal, a major rail and heavy industrial complex spread along the banks of the narrow Wupper river valley. Beginning the night of May 29, 1943, the British sent 719 planes to drop 1,900 tons of bombs on the area. 2,450 civilians died, Bayer was out of production for nearly two months, and Arends' nursery was destroyed.

Julia Brittain says Arends, then nearly 80, never fully recovered. Paul Temple landed with the D-Day invasion of June 6, 1944, and remembered helping the crippled nursery smuggle seedlings to Harold Hillier in England.

After the war, Arends' two sons kept the operation running. In 1950, the old man began working with a dwarf azalea seedling. Then in 1955, three years after he died, Herbsfreude was released as a hybrid between Sedum spectabile, a pink-flowered ornamental from the lowlands of northeastern China and Korea, and Sedum telephium maximum, a highly variable European native.

In the middle sixteenth century, Hieronymus Bock had reported extracts of telephium were used in the Rhine valley to treat internal injuries like ulcers of the lungs. A century later, Nicholas Culpeper said a bruised leaf or the sap from orpine was used in England to treat external wounds. However by the time, Georg Arends was active, the old herbal remedies, like the dye plants, had been displaced by chemists.

Now, medical researchers are isolating the active ingredients from those traditional medicine plants and testing their efficacy. In the early 1990's, researchers in Munich identified two polysaccharides in telephium that were anti-inflammatory. A few years later, Italian scientists observed the ways the polysaccharides and flavonols operated on cells during wound healing. Last year, another Italian group described the biochemical processes involved in abating inflamation.

Bayer may have reemerged from Allied control in 1951 a much smaller company, but it has since reconglomerated, and now even makes the lawn pesticide sold in the local hardware that uses synthetic pyrethrum. Arends' granddaughter, Anja Maubach, still has the nursery in Ronsdorf. Herbsfreude is sold as Autumn Joy, and botanists have decided that spectabile and telephium aren’t really sedums after all, but members of a related genus they call Hylotelephium.

Notes:Altavilla, Domenica, Francesca Polito, Alessandra Bitto, Letteria Minutoli, Elisabetta Miraldi, Tiziana Fiumara, Marco Biagi, Herbert Marini, Daniela Giachetti, Mario Vaccaro, Francesco Squadrito. "Anti-Inflammatory Effects of the Methanol Extract of Sedum telephium ssp. maximum in Lipopolysaccharide-Stimulated Rat Peritoneal Macrophages," Pharmacology 82:250-256:2008.

Bock, Hieronymus. Kräuterbuch, 1539, cited by Culpepper.

Brittain, Julia. The Plant Lover’s Companion, 2006.

Culpeper, Nicholas. Culpeper’s Complete Herbal and English Physician, 1650's, 1826 edition republished in 1981.

Obituary for Paul Temple, The Telegraph, 24 February 2007.

Raimondi, L., G. Banchelli, D. Dalmazzi, N. Mulinacci, A. Romani, F. F. Vincieri, and R. Pirisino. "Sedum telephium L. Polysaccharide Content Affects MRC5 Cell Adhesion to Laminin and Fibronectin," Journal of Pharmacy and Pharmacology 52:585-591:2000.

Sendl, A, N. Mulinacci, F. F. Vincieri, and R. Wagner. "Anti-inflammatory and Immunologically Active Polysaccharides of Sedum telephium," Phytochemistry 34:1357-62:1993.

Photograph: Autumn Joy sedum, 7 September 2009.

Sunday, September 06, 2009

Clammy Weed

What’s blooming in the area: Tamarix, tea roses, Apache plume, trumpet creeper, Japanese honeysuckle, silver lace vine, leather leaved globemallow, alfalfa, white sweet and white prairie clovers, velvetweed, scarlet beeblossom, white and yellow evening primroses, datura, Heavenly Blue and ivy-leaf morning glory, scarlet creeper, bindweed, goats’ head, purple phlox, bouncing Bess, pale trumpet, stickleaf, clammy weed, spurge, purslane, pigweed, Russian thistle, amaranth, winterfat, ragweed, snakeweed, native and farmer’s sunflowers, áñil del muerto, Hopi tea, gumweed, horseweed, wild lettuce, purple, strap-leaf and hairy golden aster, woolly paper flower, goldenrod, tahokia daisy, black grama grass; buds of heath asters; seeds on bittersweet and burr grass; some corn stalks turning brown; grass and alfalfa hay cut; apples falling.

What’s blooming in my yard, looking north: Zucchini, nasturtium, Mexican hat, chocolate flower, blanket flower, black-eyed Susan, chrysanthemum.

Looking east: Floribunda rose, hosta, California and Shirley poppies, hollyhock, winecup, sidalcea, snapdragons, Maltese Cross, Jupiter’s beard, coral beardtongue, large-leaved soapwort, sedum, garlic chive, Maximilian sunflower.

Looking south: Blaze roses, rose of Sharon, sweet pea, Crimson Rambler and reseeded morning glories, zinnia, cosmos.

Looking west: Caryopteris, butterfly bush, Russian sage, catmint, calamintha, lady bells, flax, sea lavender, David phlox, leadplant, perennial four o’clock, purple ice plant, Silver King artemisia, purple coneflower, Mönch aster.

Bedding plants: Moss rose, sweet alyssum; ripe tomatoes.

Inside: South African aptenia.

Animal sightings: Rabbit, geckos, hummingbird, bees, large black harvester and small dark ants, grasshoppers.

Weather: Rain last rain Sunday; 13:05 hours of daylight today.

Weekly update: When clammy weed began blooming the end of July it resembled phlox, a round white head topped a tall, straight stem that rose from a bed of three-part, clover-like leaves.

Now it’s been out for more than a month it looks more like mustard. The individual florets terminate maroon stems that reach up and out from narrow leaves. Each flower begins as a collection of four white petals surrounding a purple pistil like ancient megaliths held tight into the head. A fountain of purple stamens towers above.

The central stem continues to grow, and after the flowers are fertilized, the petals fall away leaving the stamens and ovary which become isolated from the head. Soon, they’re replaced by a green pod held out by the pedicel branch dropping under the weight until the plants looks like one of those many armed Hindu gods.

This member of the caper family ranges from lower Canada to the upper states of México, but it isn’t ubiquitous. John Hilty says that in Illinois the taprooted annual occurs on "sand or gravel bars along rivers, gravelly areas and clay banks along railroads, and barren waste areas." In Michigan, Edward Voss reported it grew in the southern counties with glacial till.

To the southwest of Española, the Nature Conservancy reports clammy weed grows with stickleaf species on intermittently flooded, sometimes stony alluvial flats and sandbars in central and southern Arizona where other herbaceous plants are scarce. In southern New Mexico, it’s found with local stickleaf species, datura and agave where shrubs have replaced grasses on the Jornado plain.

The nearby wide arroyo where I see the flowers runs west to the Rio Grande. The south wall is maybe seven feet high and relatively soft clay or sandy loam. A wide plain has developed at its base, edged by chamisa where the water runs. The wildflowers blooming there now include golden hairy asters and hopi tea.

The north bank is higher, with openings carved by wind and water. Bands of exposed gravel spill out, so the near floor is pebbly in places. Russian thistle and stickleaf sprouted in its shadow when the weather warmed. Clammy weed’s only found in this protected area, except for one plant that emerged in the middle of the road cut.

Despite the wide national distribution, the only native groups Dan Moerman reports using clammy weed live in Arizona and New Mexico. The Isleta south of Albuquerque rolled dried leaves in corn husks for ceremonial cigarettes while the cactus fraternity of the Zuñi rubbed chewed a’pilalu roots and flowers on wounds after members were whipped by willow and cactus switches.

It’s limited use by tribes may be a function of the sporadic nature of a summer annual that depends on soil, rain and temperature conditions to germinate, or it may result from the natural protection of the plant. The leaves and stems are sticky and stink.

Qian Shi’s team at the University of North Carolina has been testing chemicals they’ve extracted from Polanisia dodecandra and found at least one is effective against a number of types of cancer cells, and another is somewhat effective. If it weren’t for all these chemicals, the plant that’s growing into a robotic toy soldier might better be known as red whiskers.

Notes:
Association for Biodiversity Information/The Nature Conservancy. "International Classification of Ecological Communities: Terrestrial Vegetation of the Western United States, Chihuahuan Desert Subset," May 23, 2000 draft available on-line.

Hilty, John. "Clammyweed," Illinois Wildflowers website.

Moerman, Dan. Native American Ethnobotany, 1998, summarizes data from a number of ethnographies including Volney H. Jones, The Ethnobotany of the Isleta Indians, 1931.

Shi, Q., K.Chen, L. Li, J. J. Chang, C. Autry, M. Kozuka, T. Konoshima, J. R. Estes, C. M. Lin, and E. Hamel. "Antitumor Agents, 154. Cytotoxic and Antimitotic Flavonols from Polanisia dodecandra," Journal of Natural Products 58:475-82:1995.

Stevenson, Matilda Coxe. Ethnobotany of the Zuñi Indians, 1915.

Voss, Edward G. Michigan Flora, volume 2, 1985.

Photograph: Clammy weed in arroyo road cut, 30 August 2009.