Broom Senecio

What’s blooming in the area: Tea roses, chamisa, áñil del muerto, broom senecio, tahokia daisies, Maximilian and native sunflowers, purple, and hairy golden asters; cottonwoods beginning to yellow.

What’s blooming in my yard: California poppy, red hot poker, snapdragon, winecup, chocolate flower, chrysanthemum, Mexican hat; leaves turning yellow on globe willow, black locust, Siberian pea, lilacs, lilies, hosta, ladybells; turning red on pasture rose, spirea; blown off roses of Sharon.

Bedding plants: Moss rose.

Inside: African aptenia and asparagus fern.

Animal sightings: Rabbit, wasp, grasshopper, large black harvester and small dark ants; large black fowl in odd places along the main road when I was leaving for work.

Weather: Rain Wednesday, frost on my car window Friday morning, fog on the river; 11:06 hours of daylight today.

Weekly update: The first hard frost, and what red or blue flowers remain lay hidden amongst cushions of seeds. It’s time for nature’s medley of yellows.

When I drive out of Santa Fe, bands of aspens loom from the distant Sangre de Cristo. When I drop down into Pojoaque, cottonwoods pick out the watercourse. Here, mossy yellow chamisa rise above the mustard snakeweeds and golden hairy asters. Clearest of all are the broom senecios.

Last weekend they peered from under chamisa shrubs in the arroyo and swayed by themselves in the sand. A few skim great mounds along the road, while the ones that have moved about my garage have clusters of six to eight skinny petaled daisies atop sparsely leaved stalks. A seed, attached to a white, dandelion-life tuft, has come up to the south by the fence that stopped its flight and a single, bright green stalk has risen from its taproot.

Broom senecios were seen by John Frémont when he was exploring the Sweet Water in Wyoming during the first part of August in 1842. One likes to imagine, when one is told someone was the first easterner to see a plant, that his report implies something about the primeval vegetation of the area.

With this groundsel, I’m not sure what past Frémont represented. Theodore Barkley suggests the plant is encountered infrequently in western South Dakota and Nebraska, and only found occasionally westward in the Great Plains, although its known in all the plains states.

The Sweet Water is the link between the South Pass through the Rocky Mountains and the river Platte that travelers followed from Missouri. A group of Astor Fur Company men had discovered the route from the west in 1812. Jedediah Smith and Thomas Fitzpatrick rediscovered what became the Oregon Trail from the east in 1823.

Soon, fur traders were using the route to bring pelts back to Saint Louis from their annual rendezvous with trappers. In 1830 the more enterprising William Sublette built a wagon road to haul his goods, a path Benjamin Bonneville used two years later to scout the area for the federal government.

By the time Frémont arrived, the trail was well established, but not yet heavily used. The valley of the Sweet Water varies from a few yards to five miles in width. He saw absinthes when he was near the mouth, and asters near the pass. Occasionally the river was bordered by "groves of willow" and nearer the pass, by aspen, beach and willow.

During his third day in the 120-mile-long valley he noted "numerous bright-colored flowers had made the river bottom look gay as a garden." Later he contrasted the occasional side valley of "deep verdure and profusion of beautiful flowers" with the "great evaporation on the sandy soil of this elevated plain, and the saline efflorescences which whiten the ground."

About the same time, he remembered seeing "many traces of beaver on the stream; remnants of dams, near which were lying trees, which they and cut down." Probably the first environmental change that favored the composites over the more valuable grasses was the death of the beavers who may have kept all those salt plains irrigated. In the mountains beyond the pass, Frémont noted both the presence of both beavers and saturated grasses.

Soon the valley would be filled with wagons in summer. The Whitmans had followed the Sweet Water in 1836, as did the wagon train of 1841 led by John Bartleson and John Bidwell and the one led by Elijah White in 1842. Fremont himself had so many men with him they needed to kill two buffalo a day to feed themselves.

Broom senecios do well in slightly disturbed soils. The only scientists I’ve read who’ve described an area dominated by the bright green subshrubs were surveying a part of the National Guard’s Camp Navajo, outside Flagstaff, that had been burned, then used for detonation exercises. The land was desolate and, no doubt, windblown, but the soil surface was not damaged the way it would have been by wagons or flocks of sheep.

In the Chihuahuan desert, others have noticed that when the soil is seriously disturbed, the thin veneer of microorganisms that sustains the grasses is destroyed and shrubs invade. The chamisas and other Chrysothamnus species protect soil nutrients while the ground between the shrubs continues to erode.

In the arroyo, the senecios growing with chamisa are taller, near 30", and have a number of stems with more clusters with more flowers crowded into the heads. The solitary plants, like those in my yard, at most have gotten 24" tall and the starry shapes of the flowers are more distinct as they overlap one another in open lattices.

In addition to its ability to survive sand and drought, Senecio spartioides was chemically prepared to protect itself from wagon train draught animals. All its parts contain pyrrolizidine alkaloids that stop most from eating them; when animals or humans do overindulge they die from liver damage.

Nature protects itself as soon as it’s disturbed. I suspect Frémont didn’t just see climax vegetation of the Great Plains, but the first response to its destruction.

Notes:
Barkley, T. M. "Asteraceae Dunn., the Sunflower Family" in Great Plains Flora Association, Flora of the Great Plains, 1986.

Evans, R. D. and J. R. Ehleringer. "Water and Nitrogen Dynamics in an Arid Woodland," Oecologia 99:233-242:1994.

Frémont, John Charles. The Daring Adventures of Kit Carson and Frémont, 1885.

Young, Erin, Abe Springer and Ty Ferré. "Frost Penetration Depth and Frost Heave at Camp Navajo: Year 1," 29 October 2004.

Photograph: Broom senecio leaning out from under chamisa in the arroyo, 4 October 2009.