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Excerpts from Jim Conrad's
Naturalist Newsletter
Entry from field notes dated August 31, 2023, taken in Los Mármoles National Park in the Eastern Sierra Madre mountains, Hidalgo state, MÉXICO, along steeply climbing road heading eastward out of town of Trancas {on maps designated "Morelos (Trancas)"} toward Nicolás Flores; juniper/pine forest on limestone bedrock; elevation ~2,200m (~7,200ft); ~N20.801°, ~W99.254°
POMBALIA VERBENACEA
On a very rocky, steep, nearly always shaded slope, the above little wildflower with its blue, two-lipped corolla at first looked like a member of the Mint Family, albeit one with only a single leaf at each stem node, not two as with most mints. However, a closer look at the flowers dispelled that idea:
The broad lower lip provided a good landing pad for pollinators, its yellow spot at the back showing the route to the nectar, as a mint flower might do. However, look at the slender, green tail, or spur, dangling from the calyx's rear. Here's a closer view:
The above shows a view of the flower from the top and a bit to one side. The corolla consists of one very expanded lower petal, and four reduced upper petals. The calyx's four upper sepals bulge at their bottoms, baglike. In the picture it appears as if the lower sepal forms the spur, but the spur is a feature of the lowest petal. Nectar is produced by a gland at the base of two of the stamens' anthers, and the spur is regarded as a nectar-storing structure.
Several kinds of wildflower produce blossoms bearing spurs, such as numerous orchid species, larkspurs, and columbines. The spurred flower type our slope flowers are most similar to are members of the Violet Family, the Violaceae. However, our plant certainly isn't a violet itself, genus Viola. The violets of North America are mostly stemless, with leaves emerging directly from the ground, and their flower petals are more equal in size. We've encountered non-violet members of the Violet Family before, however, such as the woody shrub Hybanthus yucatnensis, in the Yucatan, and an actual tree, Rinorea guatemalensis, in Chiapas. Those species display profoundly different vegetative features, but their basic Violet-Family flower and fruit structures are very similar.
The mostly tropical Violet Family worldwide currently comprises 23 genera in about 1050 or so genera. In our upland region of central Mexico, the 2021 study of José Luis Villaseñor and others entitled "Riqueza y distribución de la flora vascular del estado de Hidalgo, México" lists only two Violet-Family genera for our upland, central Mexican state of Hidalgo. One genus is Viola itself, and the other is Pombalia. Our plant is clearly not a Viola, which leaves Pombalia. One of the two Pombalia species listed produces very narrow, grasslike leaves, but pictures of the other species exhibit broad leaves and other features exactly as seen on our plant, so here we have POMBALIA VERBENACEA.
Pombalia verbenacea until 2014 was assigned to another genus, as Hybanthus verbenaceus; older treatments use that name. Our plant, known by no English name, is distributed throughout most of Mexico's highlands into Guatemala, usually in oak and oak-pine forests.
Not much information about Pombalia verbenacea is available, except as being listed as appearing at various locations. Sometimes it's described as medicinal, without further information.