Locoweed

What’s blooming in the area: Tamarix, Russian olive, Austrian copper, tea and pink shrub roses, Apache plume, snowball peaked, honeysuckle, silver lace vine, yucca, peony, fern-leaf globemallow, hoary cress, tumble mustard, stickseed, alfalfa, purple loco, scarlet beeblossom, oxalis, bindweed, blue gilia, perky Sue, fleabane, goatsbeard, native dandelion, needle, rice, June, cheat, single and three awn grasses; buds on stickleaf; buffalo gourd, purslane, tahokia daisy and ragweed up.
What’s blooming in my yard, looking north: Black locust, Dr Huey, Lady Banks and miniature roses, German iris, golden-spur columbine, chocolate flower and Moonshine yarrow; buds on catalpa, privet, hartweg, anthemis and Parker’s Gold yarrow; squash up.
Looking east: Persian yellow rose, oriental poppy, winecup, coral bells, cheddar pink, snow-in-summer, small-leaved soapwort, sea pink, Jupiter’s beard, snapdragons, rock rose, pink evening primrose, pink salvia, California poppy, Mount Atlas daisy; buds on hollyhock and Maltese cross; tomatillo up.
Looking south: Beauty bush, weigela, rugosa and rugosa hybrids, spirea, raspberry; Sensation cosmos
germinating.
Looking west: Flax; buds on catmint and sea lavender; last of the herbaceous perennials emerged, shasta daisy and perennial four o’clock; buddleia coming up from the ground.
Bedding plants: Moss rose.
Inside: South African aptenia and kalanchoë.

Animal sightings: Rabbit, humming bird, bumblebee on Apache plume, bees and flies around beauty bush, orange butterfly on locust, vicious mosquitoes, small moths, large black harvester and small red ants; cow mooing somewhere nearby Wednesday morning
Weather: Rain off and on since Thursday has penetrated a few inches into my drive, but left barely a trace in the native yard. Plants that formed their buds last year, like daffodils and spirea, had a great spring, if they missed the days with extreme temperatures; those like needle grass that rely on current conditions are having an average season. 15:33 hours of daylight today.
Weekly update: Ranchers have no problems recognizing loco weed: it’s the purplish flowered legume, with pairs of leaves spaced along its stems like feathers and odd leaflets at the tips, that kills animals by attacking their neurological systems, enlarging their hearts and congesting organs like those used for digestion.
Discovering the source of the poison was an early conundrum for the agriculture department. In 1909, Charles Marsh identified the connection to locoweeds and noted the similarity between locoism and problems caused by Swainsona in Australia. Researchers first suspected barium was the toxic agent that caused horses to treat small stones like boulders and cows to stagger. Then they investigated selenium, but found it only produced some of symptoms and didn’t appear in all areas where livestock were sickened.
Finally, in 1979, Steven Colegate’s team identified the active chemical in the Australian plant as swainsonine, and scientists like Russell Molyneaux and Lynn James confirmed its existence in the two southwestern locoweed genuses, Astragalus and Oxytropis. Now Karen Braun’s group has found a fungus living within the plants is the actual producer of the dangerous toxin.
I have no way of knowing if the Oxytropis lambertii currently blooming in my drive is dangerous. Biologists culture their samples to detect the fungus. However, Michael Ralphs’ team found only three lambertii populations of one subspecies growing in southern Utah, Arizona and southwestern New Mexico contained swainsonine. They found none of the chemical in any of the plants from the rest of Utah, eastern Colorado, and northeastern New Mexico.
Even though lambertii is the most common locoweed in New Mexico, it probably needs more moisture than exists in this area, at least 16" a year. The taprooted perennials didn’t appear until I graveled my drive, and may either have come with the truck or been lying in the soil waiting for the right conditions.
Right now, one is in the drive outside my front porch that’s survived repair trucks, one hides in the grass at the edge of the gravel to the west, and two are at the eastern edge. There have never been more than four clumps, though ones have come and gone, and they’ve never strayed from soil with water trapped by gravel. This year, two have colonized, perhaps from underground runners.
The Astragalus growing outside my neighbor’s bark-covered fence may be as harmless and as accidental. The colony didn’t appear until he built the fence and planted some fruit trees. Again, the seed may have come with the wood or been waiting for ideal conditions. The pinkish, introverted pea flowers bloomed the past two weeks downslope from where he waters the trees.
My purple flowers with white reflector blotches on their upper petals differ from his because the individual florets are spaced along bare, straight stems while his smaller racemes cluster at the tips. My Oxytropis rise from basal rosettes of five widely separated pairs of grey-looking leaflets on stalks that may stand three inches off the ground and often persists through the winter. The leaf stalks with five to eight pairs on his Astragalus splay from stem joints that also hold the flowers. There are more leaf stems than flowers, and they reach beyond the color to catch the light. My leaf segments are flattened narrow lances with pointed tips, while his are narrower, folded down the center and blunted at the ends.
Ranchers really don’t care about such variability in nature. Marsh told them all they needed to know. The seed banks that produced my flowers and those of my neighbors make locoweed nearly impossible to eradicate. It will be a while before the discovery people should control an invisible fungus on the open range has any affect on livestock losses.
Notes:Braun, Karen, Jennifer Romero, Craig Liddell, and Rebecca Creamer. "Production of Swainsonine by Fungal Endophytes of Locoweed," Mycological Research 107:980-988:2003.Colegate, Steven M., P. R. Dorling, and C. R. Huxtable. "A Spectroscopic Investigation of Swainsonine an Alpha Mannosidase Inhibitor Isolated from Swainsona-canescens," Australian Journal of Chemistry 32:2557-2264:1979.Marsh, Charles Dwight. The Locoweed Disease of the Plains, 1909.Molyneaux, Russell J. and Lynn F. James. "Loco Intoxication: Indolizidine Alkaloids of Spotted Locoweeds (Astragalus lentiginosus)," Science 216:190-191:1982.Ralphs, Michael H., Stanley L. Welsh, and Dale R. Gardner. "Distribution of Locoweed Toxin Swainsonine in Populations of Oxytropis lambertii," Journal of Chemical Ecology 28:701-707:2002.
Photograph: Oxytropis lambertii at the east end of my drive, 19 May 2009; the pink flower held at the lower left is the last of the season from my neighbor’s Astragalus.