Deep Magenta, Deep Sands, Deep Time

Leon County, Texas - April 2, 2025

Fifty minutes' drive from College Station, Texas, a luxury community sprawls across Post Oak savanna and Eocene sands. Directly at its heart lies a pocket of shifting dunes. This strip of unusual habitat - roughly 100 by 300 meters - has somehow evaded being planted to lawn, turned into overpriced homes, or excavated in favor of an artificial lake. Each spring thousands of unusual plants emerge from the white ground, a fraction of which send up globular heads of striking magenta flowers. These are the Largefruit Sand Verbena (Abronia macrocarpa), an incredibly rare plant of the four o'clock family (Nyctaginaceae) described from this very spot in 1972, and the easternmost member of its genus.

It is a miracle the site has survived. In his publication describing the species, Leo Galloway noted the following:

The collection site is in a rapidly growing resort development. The habitat has been extensively damaged by motorbikes, dune buggies, and horseback riders. Under existing conditions the species may be extinct within a few years.

The species is a little better off than Galloway feared. Good people have succeeded in maintaining just enough awareness that the type locality hasn't been swallowed by the human excess that surrounds it. Intensive survey efforts have also revealed eight other populations - some quite large - across three counties and within 80 kilometers of each other. Granted, better than nearly extinct is a low bar. This plant hasn't surpassed it by much, as none of the threats are actually gone from the type location and all populations but one exist on private land, greatly complicating the conservation of a rare species made much rarer. After all we've done, we are lucky to have the fortune of knowing Abronia macrocarpa.

The sandhills from which Abronia macrocarpa was described still suffer from ORV use, foot traffic, and other forms of unhelpful disturbance.

Oh, what a plant it is. The stem creeps along and beneath the sand, stabilizing itself against the loose substrate. Its showy inflorescences, 5-8 centimeters across, are held up to 30 centimeters above the sand. Everything beneath the petals, including the small, slightly fleshy leaves, is covered in sticky glands. Each emerging inflorescence holds about two dozen closely packed flowers, their petals tightly spiraled and hooked inward at the end. Each open flower has a long, slender calyx tube expanding into 5 slightly dissected petals. The blooms have a faint scent of roses which grows much stronger through the evening (all the better for moth pollination). Once an inflorescence finishes blooming, the pedicel reflexes strongly downward and prepares to drop its fruits, which quickly develop the large papery wings for which the species is named. Eventually these fall to the sand, where they drift a short distance before lodging against the base of a plant, a stray stick, or a small windblown ridge.

Its identity is wrapped up in its range and habitat as much as its field marks. I thoroughly enjoyed the isolated dunes and the small white grains of sand stuck to every part of the plant's sticky surface. Also enjoyable was the cast of plants growing alongside it. Many are restricted - or nearly so - to the sandy soils of Eastern and Central Texas. Species blooming while I was there included Soxman's Milkvetch (Astragalus soxmaniorum), Stemless Spiderwort (Tradescantia subacaulis), Drummond's Phlox (Phlox drummondii var. drummondii), Drummond's Nailwort (Paronychia drummondii), and Old Plainsman (Hymenopappus artemisiifolius). Not flowering but still exciting were two other rarities, neither as rare as Abronia but both restricted to the same geologic formation: Sandhill Woolywhite (Hymenopappus carrizoanus) and Parks' Jointweed (Polygonella parksii). These are all pictured below in the order they are mentioned:

If only more of this habitat - and the accompanying floral associations - was still around. Even before the Abronia was recognized by Western science, its type locality was under severe threat. The naming of the species came too late to identify, let alone protect, countless acres of suitable habitat which surely existed throughout the surrounding area. The post oak openings & barrens that the species inhabits are now essentially unrecognizable throughout its small range, with all populations relegated to small sandhill remnants or severely degraded natural communities.

As any botanist knows, this is an example of a tragedy all too common among narrowly endemic plants. There's little colonialist culture is better at than utterly devastating the landscape - in this case through agriculture, grazing, fire suppression, and residential development. It creates an illusion of extreme rarity for specialized species relegated to the islands and scraps of habitat left behind for them in the Anthropocene. In reality, the range of Abronia macrocarpa was probably once a grand mosaic of Post Oak savanna, undulating grasslands, blowing white sands, and mesic stream valleys. Its flowers were once a characteristic part of springtime in a distinctive, albeit relatively small region. Like millions of other species, this one has been robbed of the right to exist freely where it evolved. We modern botanists will never understand the full context of its existence.

We do know of some excellent geological context. Abronia macrocarpa is endemic to a small section of the Carrizo and Queen City Sands, both formed in the Middle Eocene (48-38 million years ago). You can click here and here for more in-depth information, but basically, they were deposited at the mouth of a proto-Mississippi River. This waterway emptied southeastward into an ancestral Gulf of Mexico, which reached much farther inland thanks to a sea levels at least 100 meters higher than at present. The Queen City and Carrizo Sands developed where sand dropped out as the river's flow decreased, while the lighter particles of silt and mud drifted even farther down the delta. Where Abronia is found, it grows on as much as 250 feet of nearly pure sand left by this sorting of ancient sediments.

Everything below the flared petals is covered with sticky glandular hairs, which in turn are covered in Eocene sand. This plant is a product of 45 million years of geologic history.

In short, the white sand dunes I wandered through last week are part of a formation deposited in the upper portion of an ancestral version of the Mississippi River Delta. After roughly 45 million years, the alluvial sand finds itself at the surface, creating a home for one of the rarest plants I have ever seen. I think this, like all geologic stories, is incredible.

What an honor to walk these deep sands, through and over deep time, while taking in the deep magenta blooms of Abronia macrocarpa. What a world, and what a plant. Long may it persist.