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Published In: Botaniska Notiser 128(4): 520–521. 1975[1976]. (Bot. Not.) Name publication detail
 

Project Name Data (Last Modified On 8/11/2017)
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101. Packera Á. Löve & D. Löve (ragwort)

Plants annual, biennial, or perennial, sometimes with rhizomes or stolons. Stems erect or strongly ascending, usually unbranched below the inflorescence, sometimes lined or angled, glabrous or with tangled or woolly (cobwebby) hairs. Leaves in a basal rosette (this sometimes absent at flowering) and alternate, progressively reduced in size from the stem base to tip, glabrous or with tangled or woolly (cobwebby) hairs, sessile or the lowermost short- to often long-petiolate, the bases weakly to strongly clasping the stem. Leaf blades unlobed to weakly or strongly pinnately lobed, less commonly pinnately compound, the terminal lobe or leaflet then usually larger than the lateral ones, the margins otherwise toothed or scalloped to nearly entire, the venation pinnate, the undersurface often dark purple. Inflorescences terminal and axillary from the uppermost leaves, panicles consisting of loose clusters to less commonly solitary heads at the branch tips, broadly rounded to more or less flat-topped in profile. Heads radiate (discoid elsewhere), short- to long-stalked, with numerous florets. Involucre cylindrical to slightly wedge-shaped or somewhat hemispherical, the bracts in 2 series, glabrous (cobwebby-hairy in P. tomentosa), those of the inner series 13–21, more or less flat dorsally, those of the outer series usually 3–7 (sometimes obscured by hairs in P. tomentosa) minute, ascending and usually incurved. Ray florets mostly 8–13, the corolla bright yellow, the lobe usually minutely 3-toothed at the tip. Disc corollas 4.5–7.0 mm long (including the lobes), bright yellow. Style branches with a stigmatic line along each inner margin. Fruits narrowly oblong to narrowly oblong-elliptic in outline, not flattened, 5–10-ribbed, minutely hairy or glabrous, brown to dark brown. About 60 species, North America, Asia.

A number of authors have noted the problems of delimiting species in this group and noted how, in some portions of their ranges, individual species can be difficult to determine with confidence. In Missouri, the main problem appears to be in distinguishing P. paupercula from P. plattensis, although specimens of P. aurea, P. obovata, and P. pseudaurea also are sometimes misdetermined in herbaria. Steyermark (1963) recommended that basal leaves and rootstocks should be collected to facilitate identification of species.

Barkley (1962, 1978) stated that putative hybrids tend to occur at sites where two or more species of Packera grow together. He also suggested that the changing climate at the close of the Pleistocene ice age brought together taxa that formerly were relatively isolated geographically. Various experts over the years have annotated Missouri specimens representing the following putative hybrids: P. aurea × obovata, P. aurea × paupercula, P. obovata × paupercula, and P. obovata × plattensis. Other hybrid combinations are to be expected, but they may be difficult to detect morphologically, for example P. paupercula × plattensis.

 

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1 1. Basal and lower stem leaves all deeply pinnately lobed or appearing pinnately compound; plants annual or perennial, the rootstock various

2 2. Plants annual or less commonly biennial, lacking rhizomes or stolons, glabrous or inconspicuously hairy; basal leaves usually absent at flowering; lower stem leaves with the terminal lobe or leaflet broadly wedge-shaped to nearly circular, shorter than to about as wide as long ... 2. P. GLABELLA

Packera glabella
3 2. Plants perennial or occasionally biennial, sometimes producing stolons, densely pubescent with felty hairs when young, sometimes becoming nearly glabrous by flowering time except for patches of dense, cobwebby or woolly hairs at the leaf bases and/or inflorescence branch points; basal leaves usually present at flowering; lower stem leaves with the terminal lobe ovate to elliptic-obovate (rarely much narrower), longer than wide ... 5. P. PLATTENSIS

Packera plattensis
4 1. At least some of the basal and often also lower stem leaves unlobed or at most with a pair of reduced basal lobes, the basal leaves well developed at flowering; plants perennial (rarely biennial in P. plattensis), usually producing short rhizomes (often appearing as leafy tufts or rosettes adjacent to the flowering stem) or stolons

5 3. Plants more or less persistently pubescent with felty, woolly, or cobwebby, dense hairs on the stems, leaves, inflorescence branches, involucre, and leaf undersurface

6 4. Stem leaves all or mostly with the blade deeply lobed, the margins otherwise with relatively sharp, sometimes irregular teeth; plants more or less evenly pubescent with dense, felty hairs when young, usually becoming nearly glabrous by flowering time except for patches of dense, cobwebby or woolly hairs at the leaf bases and/or inflorescence branch points ... 5. P. PLATTENSIS

Packera plattensis
7 4. Lower stem leaves with the blade unlobed or with few irregular lobes toward the base, the margins otherwise scalloped or relatively evenly and bluntly toothed; plants more or less evenly and persistently pubescent with dense, felty hairs, the leaf blades (particularly the upper surface) and upper portion of stems sometimes becoming nearly glabrous by flowering time ... 7. P. TOMENTOSA

Packera tomentosa
8 3. Plants mostly glabrous, sometimes sparsely to densely hairy along lower portion of the stems, sparsely hairy on the leaf undersurface, cobwebby-hairy in small patches at the leaf bases, or with sparse pubescence along the inflorescence branches

9 5. Basal leaves with the blades mostly tapered at the base, if truncate to shallowly cordate, then with a pair of narrow wings of tissue extending along most of the petiole

10 6. Plants producing well-developed, slender stolons; basal leaves with the blade base tapered to truncate or slightly cordate, the tissue extending along most of the petiole as a pair of narrow wings ... 3. P. OBOVATA

Packera obovata
11 6. Plants not producing stolons or rarely producing short stolons; basal leaves with the blades mostly truncate to heart-shaped, the tissue not extending along the petiole or extending along only the terminal portion of the petiole ... 4. P. PAUPERCULA

Packera paupercula
12 5. Basal leaves with the blades truncate to cordate at the base, if somewhat tapered, then with blade tissue not or only slightly extending along the terminal portion of the petiole

13 7. Basal leaves with the blade oblong-ovate to nearly circular, truncate or cordate at the base, at least some deeply cordate ... 1. P. AUREA

Packera aurea
14 7. Basal leaves with the blade oblong-ovate to broadly lanceolate, abruptly short-tapered to more commonly truncate or shallowly cordate at the base ... 6. P. PSEUDAUREA Packera pseudaurea
 
 
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