Geocarpon is a tiny, inconspicuous plant found almost exclusively on sandstone glade outcrops. Extremely rare, it is a species of conservation concern. In Missouri, it occurs only in the southwestern quarter of the state.
Geocarpon is a small, succulent annual plant growing 1½ inches tall. Young plants are dull green, sometimes tinged with red, and may become wine red as the growing season progresses.
The leaves are tiny and cup shaped, growing opposite each other along the branches.
Blooms mid-March–early May.
The flowers are green and inconspicuous, growing at the base of the leaves or at the branch tips, and may appear to be leaves themselves.
- See Life Cycle for more of the particulars about flowers, fruits, and growth pattern.
- The limited habitat and distribution are keys to identifying this small plant.
- The taxonomy of this species is currently under revision, with some researchers proposing the new scientific name Mononeuria minima.
Height: to about 1½ inches.
Geocarpon populations in Missouri are restricted to Dade, Polk, Greene, Cedar, Jasper, Lawrence, and St. Clair counties in the Ozark and Osage Plains ecoregions.
Habitat and Conservation
In Missouri, geocarpon grows in only about eight southwestern counties, on channel sandstone glades and outcrops, many less than one acre in size.
- Channel sandstone is a layer of sandstone that originated as sand deposited in a stream channel. When softer limestone layers above the sandstone wear away, the channel sandstone is exposed as ridges.
- Missouri's geocarpon populations mostly occur in an area where channel sandstone glades are concentrated in the low hills associated with the upper Sac River and its tributaries around and upstream from Stockton Lake.
Within these glades, geocarpon thrives at the base of slightly tilted rock outcrops where seepage water flows across and forms shallow, sandy or gravelly depressions.
Geocarpon declines when its preferred, harsh environment with thin, sandy soils is changed, especially when richer soils accumulate and favor competing plant species, which shade out geocarpon. Historically, wildfires spread into sandstone glades from nearby savannas, woodlands, and prairies, but humans have suppressed fires and allowed cedars, blackjack oaks, and grasses to encroach on the glades.
Restoration efforts include glade management with prescribed fire, reduction of woody vegetation, and invasive species control. Efforts are also being made to establish new populations, from seed, in protected areas.
Status
Native Missouri wildflower. A species of conservation concern, listed as endangered by the Missouri Department of Conservation and as threatened by the U.S. Fish and Wildlife Service.
Missouri holds most of the the populations of this species, though it occurs in some nearby states as well.
Life Cycle
In Missouri, geocarpon blooms from mid-March through early May. The flowers are green and inconspicuous, lacking petals, growing at the bases of the leaves or at the branch tips, and may appear to be leaves themselves.
The fruits mature from May to early June.
The plants die 4 to 6 weeks after seed set.
The following December, seeds germinate into tiny rosettes, which appear as a tiny cluster of leaves on the ground. The rosettes remain through winter and develop into mature plants the following spring.
Human Connections
Researchers are studying the roles humans play in helping or hurting the habitat this tiny plant needs:
- Suppression of natural fire allows cedars, grasses, and other plants to become established and shade out the geocarpon.
- Disturbance by cattle and other large animals, and ATV use, can churn the soil, altering its chemistry, moisture, and abundance at a site.
- In many cases, such disturbances are a detriment, but in some cases, when there is no periodic fire or other management to reduce competing vegetation, these might actually help certain populations survive.
If you can't find this minute, rare plant, keep your eyes open anyway, for there are still many wonderful, tiny things to discover: antlion traps in sandy soil, dozens of species of mosses, lichens, and mushrooms with all sorts of curious shapes, and hundreds of other amazements.
Ecosystem Connections
Geocarpon is in the same family as carnations, catchflies, chickweeds, and pinks.
Other species that live in the harsh, hot habitats of southwest Missouri's channel sandstone glades are Nuttall's sedum (or yellow stonecrop, Sedum nuttallianum), pink purslane (Portulaca pilosa), and a fishscale lichen (Psora icterica).Many animals are specialized for life in the desert-like habitat of glades, too.
