Recently, I got back from a trip to southwestern Missouri- an area with a ton of unusual, rare, tiny plants found on exposed sandstone barrens and glades. These go mostly ignored by visitors to this region, who usually go for bass, boating and Branson. As a botanist who absolutely loves the miniature, however, I was thoroughly enthralled.
Obviously the above looks like a boring field to the average person, albeit with some exposed rock. The majority of the brown grass above is Little Bluestem, which is at least native but pretty abundant throughout the Eastern US. The dead, dull appearance hides a complex little living world.
The thin layer of soil restricts access to water for most plants, and most of that water falls as spring rains. As a result, most glade-dwelling flora either store water (like the Phemeranthus species above) or bloom early on the in spring and die back by summer’s heat. This second category goes by the name spring ephemeral.
The most obvious of the ephemerals here is the bright yellow Corydalis aurea, or Golden Smoke. Despite being less than a foot tall, this species still only grows on the deeper pockets of soil within the sandstone glade.
The same goes for False Garlic, an ever-present sight across the landscape of southwestern Missouri, it seems. Any sunny, well-drained habitat seems to be fine for this species, which uses sandstone glades just as readily as it uses limestone ones, and just as much as it uses nearby prairies and unmowed fields.
The shallowest areas here, however, support only a few plants, many of them specialists. Of those, the most rare is Geocarpon. This bizarre little plant only grows where a thin layer of soil, usually just the remains of a cyanobacteria colony, has developed on the bare sandstone exposed in patches. The sandstone present must be high in salts or magnesium, as this stunts the growth of competition and seems to be required for Geocarpon to thrive. This dime sized plant sprouts, blooms, and dies in a month, so it takes good timing to catch. I caught it at the end of its season- it’ll be virtually impossible to find even the dead stems by the end of May. Geocarpon’s specificity of habitat makes it rare, and it is federally listed as threatened for that very reason.
Few other plants grew around Geocarpon, the major exception being a strange little plantain with extremely narrow leaves. This species is either Plantago elongata or Plantago pusilla, depending on who you ask. I lean elongata for this particular population. Note the tip of my index finger in the above photo for a good idea of how tiny these are.
Around the edges of the habitat, Eastern Redcedars take over any deeper patches that are undisturbed. In a more natural setting, or at least for the last few thousand years, fires regularly burned away the redcedars and some of the dirt, leaving the bedrock exposed. In lieu of fire, the power line company does a good job, since they remove the junipers to prevent them interfering with power lines. Still, outside the cut, the trees grow back in, and some other partial-shade loving plants come in as well. One of those is Violet Collinsia, seen above en masse and below by itself.
This region supports a number of barrens species of the Western Ozarks/Southern Great Plains whose ranges all seem to center around Fort Smith, Arkansas, roughly. Collinsia violacea is slightly more widespread than that but follows a similar distribution. I’ve found it once before, on the sand prairies south of Cape Girardeau in the Missouri bootheel.
I moved on to a second, fire-maintained glade a short drive away from the first one. This second one lacks Geocarpon but it does have a number of other unusual plants and preserves a better habitat matrix. I’m not sure that there’s a good definition separating glade and barren- personally I use the term glade to describe a shallow-rock habitat with less than 10% tree cover, while I call such habitats with 20% or more tree cover barrens. However, their use is interchangable and both refer to the shallow, open habitats where bedrock approaches the surface.
The second site supported a number of shallow drainages and sandstone pools. These pools are only full of water during the spring rains and are thus known as vernal pools.
The wet moss patches near the sandstone pools supported a large population of Golden Selenia, an uncommon ephemeral mustard and one of the brightest plants flowering here.
Some had even gone to seed, showing off the typical mustard family siliques, though none were ripe. By midsummer these plants will be gone as the habitat dries, so large, pollinator-friendly flowers are a necessity to ensure their continued survival. Based on the bees I saw there, they’re doing pretty well.
I followed the stream further down, coming to a deeper vernal pool with shallow, silted over edges. Here a number of tadpoles and mayfly larvae resided. Like the surrounding plants, these species take advantage of the spring rains to use the vernal pools before they dry up. Heck, even in the pools a few species of plants occured.
Not all species rely solely on spring rains. Sedum nuttallii grows in crevices and cracks throughout the sandstone glade here, and its succulent leaves store water for dry periods. However, this species is also ephemeral, though it flowers a bit later in the year when more pollinators are active.
While this time of year is dominated by annual, ephemeral flowers, there’s still quite a few perennials. The small, needlelike leaves of Selaginella rupestris reduce water loss, and the plant can go dormant between rains, but it survives as a mat of stems year-round on this habitat.
In slightly shaded areas around the edges, more perennial plants can compete, and species like this Blue Ridge Blueberry grow- perennials with a high degree of tolerance for drought, but which require slightly less extreme conditions than a thin veneer of soil over bare rock.
About this time, the spring rains decided to return, and I left the land of miniatures to go enjoy my nice dry car. Glades are fun, but I’m no Selaginella, and I can’t just go dormant when conditions shift, so I shifted my conditions back to my room for the night.
At some point I’ll cover the limestone glades, especially the dolomite ones with which I’m much more familiar, having spent a fair bit of time on them when I was actively not on this blog. In the meantime, go check out your local glades or barrens- there’s a lot more going on than you expect!