Flora of Georgia and surrounding states
Granite Outcrop Plants
Diamorpha smallii Britton ex Small 1903, elf-orpine
If I had to choose "the" plant of granite outcrops, there is really no other choice than elf-orpine. I'm sure that on any outcrop of at least a quarter of an acre in the entire southeastern Piedmont one will find this plant. Whenever I walk on outcrops, this is the first plant I look for. It is a member of the Crassulaceae.
Taxonomy
Thomas Nuttall recognized before 1817 that this plant's capsule opens with a valve rather than along the ventral suture like all the other stonecrops (see photos at the bottom of this page that shows the structure of the fruit) and made note :
"Having never seen this plant in flower, I am unable to ascertain its genus; it is, however, at the same time much more nearly related to Tillaea, than to Sedum. In the structure of the capsule it entirely differs from every other plant in the Natural Order Sempervivae." (The genera of North American plants, and a catalogue of the species, to the year 1817, by Thomas Nuttall.)
So he places it in Tillaea as "Species 1 T? cymosa" with then known Sedum pusillum Michaux as a synonym (page 110). At the same time he creates the monotypic (containing only one species) genus Diamorpha as very distinct from Sedum and Tillaea for Diamorpha pusilla yet comments that "this genus should have been placed in Octandria tetragynia" after Pursh (page 293). Today we recognize that Diamorpha smallii and Sedum pusillum are very distinct plants and it is impressive that Nuttall was so observant so long ago.
All this makes for a bit of complicated synonymy (see chronology below). John Kunkel Small, the incredible botanist of the southeastern United States, had a similar eye for tiny differences. He followed the now abandoned American Code of Botanical Nomenclature which uses all sorts of names now not recognized. Its rules were more lax and names could be created without full description. The "ex" before his name in authority indicates he used the name first but it was "legitimized" under the then International Code of Botanical Nomenclature by the name before, in this case Nathaniel Lord Britton in 1903. Two years later Britton published them as his own, now considered presumptuous.
Small collected a plant at the falls of the Yadkin River in North Carolina in 1896 he considered distinct from Diamorpha cymosa. Britton named it Diamormpha smallii in his honor in 1905. Because of the confusion between Diamorpha cymosa and Sedum pusillum, the name Diamorpha smallii is preferred as it carries no ambiguity.
With the mid-20th century trend toward lumping, it was moved into Sedum. Current research supports segregating out as Diamorpha smallii.
Synonyms
Tillaea? cymosa Nuttall 1818
Diamorpha pusilla Nuttall 1818
Diamorpha cymosa (Nuttall) Britton ex Small 1903
Diamorpha smallii Britton ex Small 1903
Diamorpha smallii Britton 1905
Sedum cymosum var. smallii (Britton) Fröderström 1936
Sedum smallii (Britton ex Small) H.E. Ahles 1964
Etymology
The name of the genus comes from the Greek διά, dia, different and μορφή, morphe, form; that is, different from sedums.
The epithet honors American botanist John Kunkel Small (1869-1938). His doctoral thesis, Flora of the Southeastern United States, was published in 1903 and expanded in 1913 and 1933 has been the standard for the region until Alan Weakley's flora was made available on-line as he works on it.
The common name refers to the very small stature of this stonecrop, which are sometimes called orpine. The Old French word orpiment for the yellow mineral arsenic trisulphide was applied to the common yellow stonecrop as orpin. Curiously, the most commonly used name today is diamorpha!
Status
No federal or state status.
NatureServe status is G4 - Apparently Secure.
Distribution & Habitat
Strictly limited to vernal pools on hard, crystalline rock, usually granite or gneiss but also occurs on sandstone outcrops on Broxton Rocks in Coffee County,Georgia and the flat sandstone ridge of Lookout Mountain above the Little River in Chatooga County Georgia and DeKalb and Cherokee counties, Alabama where the boundary line follows the river.
The Biota of North America has a county-level distribution map.
The UNC Atlas has a county-level distribution map.
Description
The Flora of North America has a detailed botanical description.
Taxonomy
Thomas Nuttall recognized before 1817 that this plant's capsule opens with a valve rather than along the ventral suture like all the other stonecrops (see photos at the bottom of this page that shows the structure of the fruit) and made note :
"Having never seen this plant in flower, I am unable to ascertain its genus; it is, however, at the same time much more nearly related to Tillaea, than to Sedum. In the structure of the capsule it entirely differs from every other plant in the Natural Order Sempervivae." (The genera of North American plants, and a catalogue of the species, to the year 1817, by Thomas Nuttall.)
So he places it in Tillaea as "Species 1 T? cymosa" with then known Sedum pusillum Michaux as a synonym (page 110). At the same time he creates the monotypic (containing only one species) genus Diamorpha as very distinct from Sedum and Tillaea for Diamorpha pusilla yet comments that "this genus should have been placed in Octandria tetragynia" after Pursh (page 293). Today we recognize that Diamorpha smallii and Sedum pusillum are very distinct plants and it is impressive that Nuttall was so observant so long ago.
All this makes for a bit of complicated synonymy (see chronology below). John Kunkel Small, the incredible botanist of the southeastern United States, had a similar eye for tiny differences. He followed the now abandoned American Code of Botanical Nomenclature which uses all sorts of names now not recognized. Its rules were more lax and names could be created without full description. The "ex" before his name in authority indicates he used the name first but it was "legitimized" under the then International Code of Botanical Nomenclature by the name before, in this case Nathaniel Lord Britton in 1903. Two years later Britton published them as his own, now considered presumptuous.
Small collected a plant at the falls of the Yadkin River in North Carolina in 1896 he considered distinct from Diamorpha cymosa. Britton named it Diamormpha smallii in his honor in 1905. Because of the confusion between Diamorpha cymosa and Sedum pusillum, the name Diamorpha smallii is preferred as it carries no ambiguity.
With the mid-20th century trend toward lumping, it was moved into Sedum. Current research supports segregating out as Diamorpha smallii.
Synonyms
Tillaea? cymosa Nuttall 1818
Diamorpha pusilla Nuttall 1818
Diamorpha cymosa (Nuttall) Britton ex Small 1903
Diamorpha smallii Britton ex Small 1903
Diamorpha smallii Britton 1905
Sedum cymosum var. smallii (Britton) Fröderström 1936
Sedum smallii (Britton ex Small) H.E. Ahles 1964
Etymology
The name of the genus comes from the Greek διά, dia, different and μορφή, morphe, form; that is, different from sedums.
The epithet honors American botanist John Kunkel Small (1869-1938). His doctoral thesis, Flora of the Southeastern United States, was published in 1903 and expanded in 1913 and 1933 has been the standard for the region until Alan Weakley's flora was made available on-line as he works on it.
The common name refers to the very small stature of this stonecrop, which are sometimes called orpine. The Old French word orpiment for the yellow mineral arsenic trisulphide was applied to the common yellow stonecrop as orpin. Curiously, the most commonly used name today is diamorpha!
Status
No federal or state status.
NatureServe status is G4 - Apparently Secure.
Distribution & Habitat
Strictly limited to vernal pools on hard, crystalline rock, usually granite or gneiss but also occurs on sandstone outcrops on Broxton Rocks in Coffee County,Georgia and the flat sandstone ridge of Lookout Mountain above the Little River in Chatooga County Georgia and DeKalb and Cherokee counties, Alabama where the boundary line follows the river.
The Biota of North America has a county-level distribution map.
The UNC Atlas has a county-level distribution map.
Description
The Flora of North America has a detailed botanical description.
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Diamorpha is a winter annual. This means that the plant completes its entire life-cycle in less than a year and sprouts in the fall with the flowers and fruits in the spring. When the fruits are fully formed, the plant dies.
There is nothing on these outcrops that a normal person would call soil. Many places on the outcrops are just a bit flatter than areas around them and sand accumulates in them. Special structures called solution pits from from the result of the action of carbonic acid (H2CO3) released by both lichens and plants that grow on the rock and the erosive force of flowing water. In these places where just enough sand and organic matter accumulate in a fragile state of stability, the seeds accumulate and when the moisture and temperature are right, germinate. These conditions occur after the summer heat when the fall rains have a chance to moisten the gravel. For most of the winter, diamorpha is just a collection of little balls or succulent green, usually forming a very tight rosette and hugging the surface of the rock as these young plants are doing at the St. Mary's outcrop on Kennesaw Mountain on January 18, 2009. |
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With such a thin stratum of "soil" to grow in, the buds are subjected to the vagaries of the winter weather. Extended periods—more than a week—of drought are common. The tiny plant must be able to deal with this lack of water and the succulent leaves that have been storing water as it was available are called on to now provide it with water for sustenance.
The extreme solar energy is also a problem for the plant and the outer layer of the succulent leaves turn a bright shade of red with an abundance of anthocyanins that act as a sunscreen that protects interior cells from high-light damage by absorbing blue-green and ultraviolet light, thereby protecting the tissues from photoinhibition, or high-light stress that reduces the production of sugar in photosysnthesis.
Note the water runoff flats in the left photo and a well-developed solution pit on, both on Arabia Mountain .
The extreme solar energy is also a problem for the plant and the outer layer of the succulent leaves turn a bright shade of red with an abundance of anthocyanins that act as a sunscreen that protects interior cells from high-light damage by absorbing blue-green and ultraviolet light, thereby protecting the tissues from photoinhibition, or high-light stress that reduces the production of sugar in photosysnthesis.
Note the water runoff flats in the left photo and a well-developed solution pit on, both on Arabia Mountain .
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As the winter days begin the lengthen after the solstice, the little buds of green begin to expand and several stems grow out radially from the base of the original rosette, with a tiny rosette at the end. As the stems elongate, so do the nodes between the succulent leaves and there begins to develop a separation between them. On flat rock outcrops where water is only present for a relatively short time after rains, the stems elongate in direct relationship with the availability of water. A wet winter means long stems, a dry winter means short stems.
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If the plant is growing in a solution pit with a depth of 3 to 6 inches, water retention is less a problem as evaporation has a great deal more work to do. With abundant pooling water, the stems of the tight rosette elongate and succulent leaves become buoyant in the water that often submerges the plant. This is often the case in the well-developed solution pits atop Arabia Mountain where this photo was taken on March 20, 2013.
The green rosettes of linear leaves in the background are of the federally endangered black-spored quillwort, Isoetes melanospora Engelmann 1877. |
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Come "income tax day" (April 15) on a normal year and the stems have all grown vertically and elongated from 2 to 4 inches and topped with a cyme* of 1 to 8 flowers. Since diamorpha has such a limited suitable environment and is of such small stature, the seeds don't spread far and usually hundreds to thousands of plants grow in a very small area. I a season with the right water conditions, the plants can form a sea of red before they flower followed by a sea of white when the flowers develop. The can completely fill solution pits where the depth of the "soil" never gets greater than an inch or so.
The visual glory of bare rock punctuated by round seas of red and white is nothing short of spectacular. * a cyme is a determinate inflorescence where the terminal (end) flower develops first and the flowers open toward the main stem. |
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Few observe diminutive things closely, and thereby miss an entirely new and fascinating world. The mass of white flowers is beautiful enough, but each individual flower is a world of its own.
Each flower has four connate (connected) sepals that hide below the four white or slightly pink petals. The petals are linear with a broadly acuminate (tapering to a point) tip. On a close look, as with a hand lens, they look almost crystalline. The eight stamens have a dark red anther that opens with ball-like grains of bright yellow pollen. The style arises taller than the stamens and splits into a three anthers with short glands surrounding them like a bottle brush. The four erect pistils, hiding behind the filaments, are joined for half of their length. The white petals contrast beautifully with the bright red succulent leaves. |
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As the fruits develop into a capsule, the pistils separate into a cruciate (cross-like) pattern. Inside each are 2 to 12 tiny seeds. When the seeds are fully formed, the entire plant dies. All the succulent leaves give up all their water and wither away. The stems constrict as they dry, becoming hard, stiff and gray. When the heat of summer is over, the capsules open with a valve on the lower side, easily visible in the right photo. All other stonecrops open along the joint or suture along the ventral (bottom) side, and split open like a canoe. If the capsule opens and seeds spill out on to 100°F + rock surface, they will die. The wiry stems are critical to their survival during the hot summer months. Just a couple of inches is the difference between life and death. Be ever so careful when walking on the sandy solution pits during the "dead" periods of summer, as while the plant is dead, the seeds are not.
