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  • 21 Aug, 2019

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Symphyotrichum Kentuckiense
Basionym

  • Aster kentuckiensis Britton

Symphyotrichum kentuckiense (formerly Aster kentuckiensis) is a rare species of flowering plant in the Asteraceae family and is commonly known as Kentucky aster, Price's aster, Miss Price's aster, Sadie's aster, or lavender oldfield aster. It is a perennial, herbaceous plant that is endemic to broken limestone cedar glades and roadsides in Alabama, Georgia, Kentucky, and Tennessee. It blooms from August through October, reaches heights between 30 centimeters (1 foot) and 100 cm (3.3 ft), and has green to reddish-brown stems. It is a nearly hairless plant with blue to blue-violet ray florets.

Symphyotrichum priceae was once considered the name of the plant, with S. kentuckiense and Aster kentuckiensis placed as its taxonomic synonyms. In 2021, botanist Max E. Medley proposed that this treatment was incorrect. As of October 2022, what was originally described as Aster priceae was accepted to be the hybrid between S. kentuckiense and Symphyotrichum pilosum var. pilosum and has been named Symphyotrichum × priceae. The hybrid is a somewhat hairy plant rather than a hairless one, and its characteristics are intermediate between its parents.

NatureServe considers S. kentuckiense Apparently Secure (G4) globally and Imperiled (S2) in Kentucky where the holotype was collected near Bowling Green in October 1898 by botanist Sadie F. Price. Aster kentuckiensis was then formally described by botanist Nathaniel Lord Britton in 1901.

Description

Symphyotrichum kentuckiense is a rare perennial, herbaceous plant endemic to areas of Alabama, Georgia, Kentucky, and Tennessee in the southeastern United States. It flowers from August through October, growing to heights between 30 centimeters (1 foot) and 100 cm (3.3 ft) from a cespitose rootstock. The rootstock has short, branched underground caudices and no rhizomes.

Stems

S. kentuckiense has from one to three or more glabrous (hairless) stems extending from the root base. These stems can be decumbent, growing horizontally along the ground and turned up at the ends, to ascending. They are green to reddish-brown.

Leaves

The species has thin alternate leaves that are dark green to bluish-green with glabrous faces. Leaves occur at the base, on stems, and on inflorescence branches. Depending upon the locations of the leaves on the plant, the apices, or tips, can be noticeably pointed (acute to acuminate), obtuse, mucronate, or cuspidate.

Basal leaves are either without leafstalks (called petioles), making them sessile, or they have very short petioles with sheathing wings that are fringed with hairs on their edges, making them ciliate. The basal leaves are oblanceolate to obovate with obtuse apices, and their bases are cuneate (wedge-shaped) to attenuate. Their margins (edges) are entire, meaning they are smooth with no teeth or lobes. Rarely, they can be sparsely saw-toothed, also called serrate. Basal leaves range in lengths from 10 to 70 millimeters (0.4 to 2.8 inches) and widths from 3 to 5 mm (0.12 to 0.20 in). The basal leaves grow in a rosette that develops prior to flowering. These leaves wither or die during plant growth, and at the time of flowering, another rosette of basal leaves forms.

Lower and middle stem leaves are sessile or may have petioles with narrow wings. They usually wither by the time the plant flowers. The leaves are oblanceolate to linear-oblanceolate and range in lengths of 70 to 105 mm (2.8 to 4.1 in) and widths of 2 to 4 mm (0.08 to 0.16 in). They have attenuate to cuneate bases that can be auriculate (shaped like earlobes) or clasp the stem.

The linear-lanceolate to narrowly subulate distal leaves are sessile and get progressively smaller as they approach the flower heads. Distal leaf bases are subauriculate (somewhat earlobe-shaped) and can clasp the stem. Their margins are entire but have cilia closer to the branches. These leaves are glabrous on both sides and range in lengths of 5 to 65 mm (0.2 to 2.6 in) and widths of 1 to 4 mm (0.04 to 0.16 in). The small, 3-nerved inflorescence leaves are often formed in clusters called fascicles.

Flowers

Symphyotrichum kentuckiense is a late-summer and fall blooming perennial, with flower heads that are about 25 mm (1 in) wide and have blue, blue-violet, pink, or purple ray florets opening August through October. The flower heads grow in leafy paniculiform to racemiform arrays on inflorescences that are straight and ascending or can have wide angles between the branches. Divaricate branching can cause the plant to appear as a small shrub. At times, the flower heads can be secund, appearing on one side of the branch.

Each flower head is on a glabrous peduncle that ranges from 4 to 20 mm (0.16 to 0.79 in) in length. There are 3 to 6 linear to subulate and stiff, glabrous bracts on each peduncle. Bracts closest to the heads can be so long that their lengths exceed the heights of the involucres.

Involucres and phyllaries

On the outsides of the flower heads of all members of the family Asteraceae are small bracts that look like scales. These are called phyllaries, and together they form the involucre that protects the individual flowers in the head before they open. The involucres of Symphyotrichum kentuckiense are cylindric in shape and usually 5.5 to 7.1 mm (0.22 to 0.28 in) in length, although they can be as short as 4.5 mm (0.18 in) and as long as 8.5 mm (0.33 in).

The glabrous phyllaries of S. kentuckiense are in 4 to 6 unequal to subequal rows, linear-subulate in shape, and gradually acuminate. The margins of each phyllary may appear white or light green but are translucent. The phyllaries have green chlorophyllous zones that are diamond-shaped to lanceolate with apices that are acute to long-acuminate, mucronate to apiculate, such that they could be tapering to a slender point. They are revolute (they roll inwards on the margins) and spread away from the head.

Florets

Each flower head is made up of ray florets and disk florets. The 20 to 28 ray florets grow in one series and are usually blue-violet, rarely white. They are usually between 9 and 15 mm (0.35 and 0.59 in) in length, but can be as short as 7 mm (0.28 in) and as long as 19 mm (0.75 in). They are 0.6 to 2.1 mm (0.02 to 0.08 in) wide.

The disks have 33 to 51 florets that start out as yellow and after opening, turn brown after pollination. Each disk floret is 3.4 to 4.6 mm (0.13 to 0.18 in) in depth (sometimes up to 5 mm (0.2 in)), and is made up of 5 petals, collectively a corolla, which open into 5 lanceolate lobes comprising 0.5 to 1 mm (0.02 to 0.04 in) of the depth of the floret.

Fruit

The fruits (seeds) of Symphyotrichum kentuckiense are not true achenes but are cypselae, resembling an achene but surrounded by a calyx sheath. This is true for all members of the Asteraceae family. After pollination, they become tan to brown with an obovoid shape, 1.5 to 2.1 mm (0.06 to 0.08 in) in length with 4 to 5 thin nerves, and with a few stiff, slender bristles on their surfaces (strigillose). They also have tufts of hairs (pappi) which are white and 3 to 5 mm (0.12 to 0.20 in) in length.

Chromosomes

The species has a monoploid number (also called base number) of eight chromosomes (x = 8). It has eight sets of its chromosomes, meaning it is octaploid, giving it a total chromosome count of 64.

Taxonomy

Classification

Symphyotrichum kentuckiense is classified in subgenus Symphyotrichum section Symphyotrichum subsection Porteriani. This subsection contains four species in addition to S. kentuckiense: S. depauperatum, S. parviceps, S. pilosum, and S. porteri. It is the only octaploid within the subsection.

Symphyotrichum cladogram
  • Symphyotrichum
    subg. Chapmaniana

    S. chapmanii

    subg. Astropolium
    subg. Virgulus
    subg. Ascendentes
                                                                                      

    S. ascendens

    S. defoliatum

    subg. Symphyotrichum
    sect. Conyzopsis
    sect. Occidentales
    sect. Turbinelli

    S. turbinellum

    sect. Symphyotrichum
    Cladogram references
    1. ^ Nesom, G.L. (September 1994). "Review of the Taxonomy of Aster sensu lato (Asteraceae: Astereae), Emphasizing the New World Species". Phytologia. 77 (3) (published 31 January 1995): 141–297. ISSN 0031-9430. Retrieved 23 August 2021 – via Biodiversity Heritage Library.
    2. ^ Semple, J.C.; Heard, S.B.; Brouillet, L. (2002). "Cultivated and Native Asters of Ontario (Compositae: Astereae)". University of Waterloo Biology Series. 41. Ontario: University of Waterloo: 1–134.
    3. ^ Sugbenus Ascendentes is made up of two allopolyploid species with historic parents from subg. Virgulus and subg. Symphyotrichum.

History

The basionym of Symphyotrichum kentuckiense is Aster kentuckiensis. Its name with author citations is Symphyotrichum kentuckiense (Britton) Medley. The plant was formally described as a unique species and named Aster kentuckiensis Britton by botanist Nathaniel Lord Britton in 1901 in his publication Manual of the Flora of the Northern States and Canada. The sample that was used by Britton as the holotype for A. kentuckiensis was collected in October 1898 by Sadie F. Price near Bowling Green, Kentucky.

Hybrid Symphyotrichum × priceae

At the same time that she collected what became the holotype for Aster kentuckiensis, Sadie F. Price collected a similar plant that Britton named Aster priceae Britton and included in its description that it is pubescent, or with soft hairs. In later floras by other authors, A. kentuckiensis was synonymized to A. priceae. In a 2021 journal article by botanist Max E. Medley, elements of the morphologies of A. kentuckiensis and A. priceae were confirmed to have been erroneously combined, and sometimes the former was ignored. Notably, this treatment resulted in floras written prior to Medley's paper applying the glabrous trait to A. priceae and S. priceae, which is incorrect, as this plant is puberulent.

In 1948, botanist Arthur Cronquist reduced Aster priceae to a variety of A. pilosus named A. pilosus var. priceae (Britton) Cronquist which Medley posited was a conclusion "based on misidentified specimens and [was] not appropriate." Subsequently, it was considered the non-hybrid species Symphyotrichum priceae (Britton) G.L.Nesom with S. kentuckiense and A. kentuckiensis as its taxonomic synonyms.

Medley suggested that the Aster priceae holotype and Britton's protologue were of the hybrid A. kentuckiensis × A. pilosus var. pilosus. He gave it the hybrid designation and acknowledged the name as Symphyotrichum × priceae (Britton) G.L.Nesom, with Aster priceae Britton as its basionym. Corrected synonyms of S. × priceae are A. priceae and A. pilosus var. priceae (Britton) Cronquist. As of October 2022, this hybrid name was accepted by Plants of the World Online (POWO). The hybrid is a puberulent plant rather than a glabrous one, and its characteristics are intermediate between its parents.

Etymology

The specific epithet (second part of the scientific name) kentuckiense is a Latinization of the name of the state of Kentucky where the holotype was found. The hybrid's specific epithet priceae is a Latinization of the surname of the collector, Sadie F. Price. The species has the common names of Kentucky aster, Price's aster, Miss Price's aster, Sadie's aster, and lavender oldfield aster. "Old field asters" is a common name for subsect. Porteriani.

Distribution and habitat

Symphyotrichum kentuckiense is endemic to a limited range in the southeastern United States, specifically parts of Alabama, Georgia, Kentucky, and Tennessee. Hybrid S. × priceae has been documented only in Kentucky. S. kentuckiense grows in the Appalachian Mountain EPA Ecoregions Ridge and Valley (67) and Southwestern Appalachians (68), and in the Interior Plateau EPA Ecoregions of Interior Low Plateaus (71) and Interior River Valleys and Hills (72). It is adapted to and known from breaks or cracks in limestone cedar glades or limestone roadsides. It can be found at 200 to 400 meters (660 to 1,310 feet) in dry soil.

S. kentuckiense is categorized on the United States National Wetland Plant List (NWPL) with the wetland indicator status rating of Facultative Upland (FACU) in the Eastern Mountains and Piedmont region (EMP). This rating means that it usually occurs in non-wetlands within its range, but can occasionally be found in wetlands.

Ecology

Symphyotrichum kentuckiense has coefficients of conservatism (C-values) in the Floristic Quality Assessment (FQA) of 7 and 8 depending on evaluation region. The higher the C-value, the lower tolerance the species has for disturbance and the greater the likelihood that it is growing in a presettlement natural community. When it grows in the Appalachian Mountain EPA Ecoregions of 67 and 68, S. kentuckiense has a C-value of 7. In the Interior Plateau EPA Ecoregions of 71 and 72, its C-value is 8. Both of these C-values mean that its populations are found in high-quality remnant natural areas with little environmental degradation but can tolerate some periodic disturbance.

Conservation

As of October 2022, NatureServe listed S. kentuckiense as Apparently Secure (G4) globally; Apparently Secure (S4) in Georgia; Imperiled (S2) in Kentucky; and, Critically Imperiled (S1) in South Carolina. The species' global status was last reviewed on 2 May 1988.