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Published In: Hortus Kewensis; or, a catalogue . . . 3: 216. 1789. (Hort. Kew.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native

 

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16. Solidago petiolaris Aiton (downy goldenrod)

S. petiolaris var. angusta (Torr. & A. Gray) A. Gray

S. petiolaris var. wardii (Britton) Fernald

Pl. 238 h, i; Map 1005

Plants with the rootstock short and sometimes branched, occasionally producing slender rhizomes. Stems solitary or more commonly few to several, 40–150 cm long, erect or ascending, finely ridged, sparsely to moderately pubescent with short, curved or occasionally stiff hairs, sometimes only sparsely hairy toward the base, not shiny, not glaucous. Leaves chiefly cauline, the largest leaves in the lower 1/3 of the stem, the basal leaves absent at flowering. Basal and lowermost stem leaves with the blade 6–12 cm long, 0.5–3.5 cm wide, variously 3–8 times as long as wide, narrowly elliptic-oblanceolate to elliptic or obovate, relatively thick and stiff, angled or tapered to a sessile or short-petiolate base, angled or more commonly short-tapered to a sharply pointed tip, the margins entire or sparsely and shallowly toothed above the midpoint and hairy, the surfaces sometimes sticky and somewhat shiny, the upper surface glabrous or somewhat roughened, the undersurface glabrous, somewhat roughened, or sparsely to moderately pubescent with minute (0.1–0.4 mm long) hairs along the main veins, with 1 main vein, the fine, pinnate secondary veins relatively easily observed (these usually forming an irregular network). Median and upper stem leaves 1–15 cm long, nearly linear to narrowly obovate, otherwise similar to the lower stem leaves. Inflorescences of axillary clusters grading into a narrow racemose panicle, the heads oriented in several directions when short ascending branches are present. Involucre 4.5–7.5 mm long, the bracts in 3–5 unequal series. Involucral bracts mostly narrowly oblong-lanceolate and sharply pointed at the tip, appressed-ascending or more commonly at least the outermost involucral bracts loosely ascending or with the tips somewhat spreading to recurved, the thin, white to yellowish white margins hairy, the outer surface glabrous or sparsely to moderately hairy, sometimes glandular and somewhat sticky, with a poorly defined, green central region toward the tip, this tapered abruptly to the midvein above or below the bract midpoint, the midvein usually noticeably thickened. Receptacle naked. Ray florets (5–)7–9, the corollas 3.5–7.5 mm long, yellow. Disc florets (8–)10–16, the corollas 4–5 mm long, the lobes 0.9–1.8 mm long, yellow. Pappus 4.0–4.5 mm long, a few of the bristles often slightly thickened toward the tip. Fruits 3–4 mm long, narrowly obovoid, glabrous or nearly so at maturity. 2n=18, 36. May–November.

Scattered mostly south of the Missouri River (Nebraska to New Mexico east to Illinois, North Carolina, and Florida). Glades, bases, ledges, and tops of bluffs, openings of mesic to dry upland forests, and savannas; also pastures and roadsides.

Steyermark (1963) noted that this attractive species performs well in the wildflower garden and that it is one of the earliest goldenrods to start flowering in Missouri. The heads are relatively large for a goldenrod.

The taxonomy of the S. petiolaris complex requires further study. On the one hand, there are problems surrounding the distinctness of S. buckleyi from S. petiolaris (for further discussion, see the treatment of that species). However, there also are problems of infraspecific variation within the species. Two elements traditionally have been accepted as occurring in Missouri (Steyermark, 1963), but different authors have emphasized different characters to separate the two. As noted by Steyermark (1963) and others (Cronquist, 1980), there is widespread intergradation between these phases. Plants that have been segregated variously as var. angusta and var. wardii have been characterized variously as having relatively narrow leaves, leaves that are sticky and somewhat shiny, leaves with the undersurface glabrous or slightly roughened, and/or involucres that are glabrous but with sessile glands. In contrast, various authors have characterized var. petiolaris as having relatively broad median and lower leaves, leaves that are not sticky or shiny, leaves with the undersurface sparsely to moderately pubescent with minute (0.1–0.4 mm long) hairs along the main veins, and/or involucres that are glabrous to more commonly sparsely to moderately hairy and sometimes somewhat sticky. The last author to study the complex was Nesom (1990d), who examined a large suite of herbarium specimens from throughout the range of the species. He concluded that there was no correlation in variation between any of the aforementioned characters. Plants from the Ozarks were most likely to have sticky, glabrescent leaves, but narrow-leaved and broad-leaved plants were equally likely to have sticky leaves. Similarly, the pubescence of the involucre varied independently of the leaf characters. Nesom concluded that for the present there is no rational way to formally subdivide S. petiolaris into varieties and that in fact a more distinctive (but still morphologically confluent) element within the range of variation occurred not in the western portion of the range but in a series of populations in the southeastern states. It remains for future studies of the population genetics of the complex to tease apart the intricate patterns of morphological variation present.

 


 

 
 
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