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Excerpts from Jim Conrad's
Naturalist Newsletter

entry dated August 15, 2022, issued from near Tequisquiapan, elevation about 1,900m (6200 ft), N20.565°, W99.890°, Querétaro state, MÉXICO
ALDAMA LINEARIS

At the edge of an overgrown hedgerow periodically watered with overflow from nearby irrigated fields, the above head-high, much-branched, stiff-stemmed bush emerged from a dense wall of assorted weeds and shrubs. Even at this distance, with numerous small florets grouped into heads, or capitula, which looked like single flowers, it was clear that this was a member of the vast Composite or Aster Family, the Compositeae.

Up close, it was a classic Composite, with petal-like ray florets radiating around the capitulum, with many smaller, cylindrical disc florets crammed into the center, their style arms extending above them like the letter Y but with the Y's arms gracefully curling beneath themselves.

From the side, the capitulum's green involucre bore several series of overlapping, scale-like bracts, with unusually long, dark green, pointed tips projecting away from the involucre. Involucral bracts come in a mind-boggling variety of shapes, forms and sizes, and these are particularly distinctive. They're even ribbed and white-hairy along their margins.

Such details as are mentioned above are mostly helpful deciding which species of a group of plants you're dealing with, but the above image of a broken-open capitulum shows us features needed for figuring out which group you have. The picture shows pale, sharp-pointed, papery scales called paleae partially wrapped around individual disc florets at their bases. Very many genera of the Aster Family produce no paleae at all.

Many genera don't produce pappi atop their cypsela-type fruits, but this genus does. In the picture, the pale, oblong, upright items at the florets' bottoms are the cypselae. Atop each cypsela, surrounding the base of the floret's yellow corolla, there's a crown-like structure composed of a low, jagged, almost white rim, and from the crown-like structure -- that's the pappus -- arise two small, thin, hard-to-see spines, or aristas. As with paleae, pappi come in all forms, and this species' pappi, despite the difficulty of seeing them, are exceptionally distinctive. Now we have some really good leads as to our plant's identity. But, to round out the profile, here's what the exceptionally small, narrow, clusters of rough-hairy leaves looked like.

Using the above details, in the Flora del Bajío covering our region, you're taken right to Viguiera linearis. However, when I check to see if at this date that's an accepted name, I find that it isn't. It's been shifted to the genus Aldama. Now it's ALDAMA LINEARIS.

Aldama linearis, endemic just to the uplands of northern and central Mexico, has no English name. In Spanish they often call it Romerillo, meaning "Little Rosemary," and it's true that our plant's slender, cluttered leaves are similar to those of the Rosemary garden herb. However, in Mexico the name Romerillo is used for lots of unrelated plants with narrow leaves. Our plant is described as frequently occurring in disturbed, weedy habitats of many kinds, at elevations of 1500-2700m (5000-9000ft).

The Rosemary-like leaves of Aldama linearis don't seem to be used as a spice, but the plant's aggressive weediness may may turn out to be useful. Yendi E Navarro-Noya and others in a 2010 study entitled "Bacterial communities associated with the rhizosphere of pioneer plants (Bahia xylopoda and Viguiera linearis) growing on heavy metals-contaminated soils" found our plant doing well in the Mexican state of Zacatecas, growing on silver mine tailings contaminated with high concentrations of heavy metals. In such a deadly environment, our plant limits erosion, keeping heavy metals from spreading into other ecosystems.

The online Biblioteca Digital de la Medicina Tradicional Mexicana reports that our plant has been cooked with horsetail plants, Equisetum laevigatum, presumably to make a "tea," to cure urination problems of all kinds. However, the main "use" local people report of the plant in a study done in the neighboring state of Guanajuato is reported to be as food for livestock. That would be the verdict here, too, with our always present flocks of roving cattle and sheep.