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Published In: Species Plantarum 2: 878. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

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25. Solidago L. (goldenrod)

Plants perennial herbs, often with short- to long-creeping rhizomes, less commonly with a short, branched, somewhat woody rootstock. Stems 1 to several, erect, ascending, or less commonly spreading to pendant, usually with few to many ascending to spreading branches above the midpoint, with fine to coarse, longitudinal ridges, glabrous or variously hairy. Basal and lower stem leaves either absent at flowering or present (and then the largest leaves on the plant), sessile or short- to long-petiolate. Stem leaves gradually or relatively abruptly reduced toward the tip of the stem either from about the midpoint or from the base, sessile or short-petiolate, the blade variously shaped, usually sharply pointed at the tip, tapered to a slender or slightly expanded but not clasping base or less commonly truncate to rounded and slightly clasping the stem, the margins entire to coarsely toothed, sometimes also roughened with minute, stout, ascending, stiff hairs, the surfaces glabrous or variously hairy. Inflorescences variously consisting of axillary clusters, or terminal, then either narrow and racemelike with clusters along the main axis or open to dense, pyramidal or flat-topped panicles, the heads solitary or more commonly in small clusters, sometimes all or mostly oriented upward (in species with pyramidal panicles), the stalks subtending the heads mostly short, usually with relatively few minute, scalelike, linear to narrowly oblong bracts to 0.4 mm long, the inflorescence branches often also with reduced, leaflike bracts conspicuously shorter than the main foliage leaves. Heads radiate. Involucre 2–8 mm long, cup-shaped to nearly cylindrical. Involucral bracts in 3–6 usually unequal, overlapping series, variously shaped, the ascending tips (the lower series sometimes spreading in S. petiolaris) rounded to bluntly or sharply pointed, the midvein 1 or less commonly 3–7 and often slightly thickened and translucent, entirely straw-colored to light yellow or with an often short, elliptic to obovate green area toward the tip, glabrous or hairy, not resinous. Receptacle flat or slightly convex, with low, toothlike ridges around the attachment points of the florets, uncommonly with a few chaffy bracts toward the margins. Ray florets (1)2–15, pistillate, the corolla well developed but relatively short, mostly spreading, yellow (white in S. ptarmicoides; see also the discussion of S. bicolor at the beginning of the Astereae treatment), not persistent at fruiting. Disc florets 2–35, perfect, the corolla relatively short, yellow (white in S. ptarmicoides), not persistent at fruiting. Pappus of the ray and disc florets similar, of numerous (25–45) slender, finely barbed bristles about as long as the corollas, the innermost sometimes slightly thickened toward the tip, white or off-white. Fruits (0.5–)1.0–4.0 mm long, obovoid to more commonly narrowly obovoid to nearly cylindrical, usually slightly flattened, often slightly several-angled in cross-section, 5–8(–10)-nerved, the surface glabrous or hairy, straw-colored to brown. About 100 species, North America, South America, Europe, Asia.

The generic concept of Solidago accepted here is broader than that embraced by some other botanists (Nesom, 1993a, 2000). In particular, some authors prefer to segregate Oligoneuron Small for six eastern North American species with generally flat-topped inflorescences, relatively broad involucral bracts with more or less parallel veins, and minute differences in achene anatomy. In Missouri, this generic controversy involves three morphologically unusual species, S. ptarmicoides, S. riddellii, and S. rigida. Anderson and Creech (1975) felt that the two groups should be united based on their investigation of leaf anatomy. Nesom’s (1993a) morphological analysis of the complex yielded ambiguous results, as did a recent molecular analysis of ITS sequences in the tribe (Beck et al., 2004). However, molecular studies of chloroplast DNA variation by Zhang (1996) supported the hypothesis that the Oligoneuron species are members of the Solidago lineage, a conclusion accepted in the floristic treatment of Ontario goldenrods by Semple et al. (1999), as well as most other recent floristic manuals for areas surrounding Missouri (Barkley, 1986; Gleason and Cronquist, 1991). The present treatment has benefited from early discussions with John Semple of the University of Waterloo concerning generic, specific, and infraspecific limits.

Two aids to identification in this morphologically variable genus are the inflorescence type and the arrangement of the leaves. Missouri species are separable into three main inflorescence types. A small group that some botanists segregate as the genus Oligoneuron (see the preceding paragraph) comprises species with relatively flat-topped or rounded, paniculate inflorescences having the heads in small clusters at the branch tips. Another group has either axillary clusters of heads or narrow, elongate terminal inflorescences that often appear spicate or racemose with the heads in small clusters along the main axis, but can have the heads oriented in several directions along short branches of a narrow panicle. The third group has often dense panicles that have been described in the literature as pyramidal. This term refers to an elongate inflorescence, sometimes nodding at the tip, with at least the lower branches arching outward or nodding, and the longest branches usually toward the inflorescence base with progressively shorter branches toward the tip. The heads are all or mostly oriented toward the upper side of each racemose branch. In a few species (like S. ulmifolia), the branches tend to be relatively widely separated along the main axis, and because the axis and branches appear leafy, these lowest branches might be interpreted as being separate inflorescences. Within this volume, to maintain continuity across the treatment of Solidago, references to a pyramidal shape apply to the overall branching pattern and disposition of heads on a single main flowering stem. Occasional depauperate individuals with small inflorescences can cause problems with the determination of all of the goldenrod species, but in such cases the orientation and position of the heads relative to the branches can be helpful in discriminating among the groups.

There are two main forms of leaf arrangement, and collectors should be careful either to gather the stem base as part of a specimen or to record the information on basal leaves carefully in the field. In some species, the basal leaves are well represented at flowering (in fact there often are few to several additional basal rosettes in proximity to the flowering stem), the basal and adjacent lower stem leaves the largest leaves on the plant, and the leaves gradually reduced from the stem base toward the tip. Some authors have referred to this leaf arrangement pattern as “basally disposed” (Cronquist 1980, 1991). In contrast, other species have the basal leaves withered and usually absent at flowering. The largest leaves occur from about 1/3–1/2 the way up the stem. This leaf arrangement is sometimes referred to as “chiefly cauline”.

Some tribes of Native Americans used goldenrods in the treatment of colds, congestion, fever, cramps, and heart ailments (Moerman, 1998). Because they are showy when in flower and often grow in proximity to wind-pollinated plants like ragweeds (Ambrosia, Asteraceae) and pigweeds (Amaranthus, Amaranthaceae) that flower at the same time of year, goldenrods have developed an undeserved reputation as causing hay fever. However, all of the goldenrods have sticky pollen that is dispersed by a variety of different insects. A number of species are attractive ornamentals in the garden and are available through wildflower nurseries. Cultivars of a few species, like S. canadensis, are more widely available in the nursery trade. Gardeners should note that some of the most widespread Missouri species, like S. altissima, can become very aggressive in the garden.

 

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1 1. Inflorescences terminal panicles (occasionally appearing as a dense terminal cluster), appearing flat-topped or rounded in overall outline, the heads solitary or in small clusters at the branch tips

2 2. Disc and ray florets white or less commonly pale cream-colored (note that the disc florets usually appear yellow because of the yellow stamens, but the corollas are white) ... 17. S. PTARMICOIDES

Solidago ptarmicoides
3 2. Disc and ray florets yellow

4 3. Leaves relatively narrow, the blade linear to narrowly lanceolate or narrowly oblanceolate, the margins entire; stems glabrous below the inflorescence, shiny ... 19. S. RIDDELLII

Solidago riddellii
5 3. Leaves relatively broad, the blade broadly oblanceolate to elliptic-obovate, ovate, or oblong-elliptic, the margins of all but the uppermost leaves usually finely scalloped or minutely and bluntly toothed; stems densely short-hairy (except in the rare var. glabrata), not shiny ... 20. S. RIGIDA

Solidago rigida
6 1. Inflorescences either consisting only of axillary clusters or, if terminal, then elongate and appearing as spikelike racemes or pyramidal panicles; if paniculate, then the heads mostly oriented upward and single or in small clusters along the branches

7 4. Inflorescences either consisting of axillary clusters or, if terminal, then narrow with small clusters or spikelike branches along the main axis, the branches not arching or nodding, the heads oriented in several directions

8 5. Basal and lowermost stem leaves the longest on the plant, usually persistent and conspicuous at flowering

9 6. Stems and leaves conspicuously hairy ... 10. S. HISPIDA

Solidago hispida
10 6. Stems glabrous below the inflorescence or nearly so; leaves glabrous on the surfaces, the margins inconspicuously hairy ... 22. S. SPECIOSA

Solidago speciosa
11 5. Basal and lowermost stem leaves somewhat smaller than the longest ones, which occur about 1/3–1/2 the way up the stem, the lowermost leaves withered or more commonly absent at flowering

12 7. Stems sparsely to moderately short-hairy, at least above the midpoint; at least the outermost involucral bracts usually loosely ascending or with the tips somewhat spreading to recurved

13 8. Leaf blades relatively broad (the largest 25–50 mm wide) and thin-textured, the margins usually sharply toothed, the undersurface moderately pubescent with short (0.4–0.7 mm long) hairs along the main veins ... 3. S. BUCKLEYI

Solidago buckleyi
14 8. Leaf blades relatively narrow (the largest 5–35 mm wide) and thick-textured, the margins usually entire or sparsely and minutely toothed above the midpoint, the undersurface glabrous or sparsely to moderately pubescent with minute (0.1–0.4 mm long) hairs along the main veins ... 16. S. PETIOLARIS

Solidago petiolaris
15 7. Stems glabrous except sometimes along the inflorescence branches; involucral bracts appressed-ascending

16 9. Leaves broadly ovate to broadly elliptic-ovate, rounded then tapered abruptly at the base to a relatively long, winged petiole (except sometimes the uppermost stem leaves); stems often strongly zigzag, especially toward the tip ... 7. S. FLEXICAULIS

Solidago flexicaulis
17 9. Leaves (except sometimes those of the basal and lowermost stem leaves, which may be broader) lanceolate, oblong-lanceolate, elliptic, or narrowly ovate, tapered gradually at the base, sessile or short-petiolate (except sometimes the basal and lowermost stem leaves); stems not or only slightly zigzag

18 10. Inflorescences axillary clusters (occasionally a few of the clusters somewhat elongate); stems glaucous ... 4. S. CAESIA

Solidago caesia
19 10. Inflorescences terminal panicles (sometimes appearing racemose or spicate); stems not glaucous ... 22. S. SPECIOSA

Solidago speciosa
20 4. Inflorescence a more or less pyramidal terminal panicle (see discussion above), often somewhat nodding at the tip, at least the lower branches arching or nodding, the heads mostly oriented upward along the racemose branches

21 11. Basal and lowermost stem leaves the longest on the plant, usually persistent and conspicuous at flowering

22 12. Stems moderately to densely pubescent with curved to spreading hairs (the pubescence sometimes slightly less dense toward the stem base)

23 13. Stems and leaves densely pubescent with minute (0.1–0.3 mm), mostly curved hairs ... 13. S. NEMORALIS

Solidago nemoralis
24 13. Stems and leaves moderately pubescent with longer (mostly 0.5–1.5 mm), mostly spreading hairs

25 14. Disc florets 8–20, the corollas 3.5–4.0 mm long ... 2. S. ARGUTA

Solidago arguta
26 14. Disc florets 4–7, the corollas 2–3 mm long ... 23. S. ULMIFOLIA

Solidago ulmifolia
27 12. Stems below the inflorescence glabrous or sparsely pubescent with mostly spreading hairs

28 15. Leaves with the upper surface strongly roughened (sandpapery) with minute, stiff, stout, broad-based (pustular) hairs ... 15. S. PATULA

Solidago patula
29 15. Leaves with the upper surface glabrous, soft-hairy, or sparsely to moderately roughened with short, stiff hairs having slender to stout, nonpustular bases

30 16. Basal and lower stem leaves with the blade broadly ovate to broadly elliptic, tapered abruptly to the winged petiole ... 2. S. ARGUTA

Solidago arguta
31 16. Basal and lower stem leaves with the blade narrowly oblanceolate to narrowly elliptic-obovate, tapered gradually to the winged petiole

32 17. Leaf blades with only 1 main vein or, if 3-veined, then the lateral pair poorly developed and only faintly visible near the leaf base

33 18. Basal and lower stem leaves tapered gradually to the petiole; ray florets 7–12, the corolla 2.0–2.5 mm long; disc florets 8–15 ... 11. S. JUNCEA

Solidago juncea
34 18. Basal and lower stem leaves tapered relatively abruptly to the petiole; ray florets 3–5, the corolla 1.5–2.0 mm long; disc florets 4–7 ... 23. S. ULMIFOLIA

Solidago ulmifolia
35 17. Leaf blades (at least of the basal and lower stem leaves) with 3 main veins for most of the length of the blade, the lateral pair well developed but sometimes thinner than the midvein

36 19. Rootstock short and branched, not producing creeping rhizomes; ray florets 5–8; receptacle naked; nodes of the flowering stem usually lacking small clusters of leaves in the axils of the main leaves ... 8. S. GATTINGERI

Solidago gattingeri
37 19. Rootstock producing creeping rhizomes, often also short and thickened at the stem bases; ray florets 7–13; receptacle frequently with a few slender, chaffy bracts toward the margin; median and upper nodes of the flowering stem usually producing small clusters of leaves in the axils of the main leaves ... 12. S. MISSOURIENSIS

Solidago missouriensis
38 11. Basal and lowermost stem leaves somewhat smaller than the longest ones, which occur about 1/3–1/2 the way up the stem, the lowermost leaves withered or more commonly absent at flowering

39 20. Stem leaves mostly short-petiolate (the uppermost leaves sometimes sessile or nearly so), the blade 1–2 times as long as wide ... 6. S. DRUMMONDII

Solidago drummondii
40 20. Stem leaves mostly sessile (the lowermost leaves sometimes short-petiolate), the blade 2–8 times as long as wide

41 21. Leaf blades with only 1 main vein or, if 3-veined, then the lateral pair poorly developed and only faintly visible near the base, the secondary veins, if visible, arranged pinnately along the midvein

42 22. Leaf blades with minute, impressed, translucent dots (these best observed on the undersurface under magnification while the leaf is held to a strong light), the margins entire ... 14. S. ODORA

Solidago odora
43 22. Leaf blades lacking impressed dots, the margins of some or all of the leaves with at least a few shallow teeth

44 23. Rootstock producing creeping rhizomes, often also short and thickened at the stem bases; ray florets 6–11; leaf blades mostly angled at the base, not tapered ... 21. S. RUGOSA

Solidago rugosa
45 23. Rootstock short and branched, not producing creeping rhizomes; ray florets 3–5; leaf blades mostly fairly abruptly tapered at the base ... 23. S. ULMIFOLIA

Solidago ulmifolia
46 21. Leaf blades with 3 main veins, the lateral pair well developed and only slightly thinner than the midvein, conspicuous in at least the basal 1/2 of the length of the blade

47 24. Stems glabrous below the inflorescence, usually glaucous ... 9. S. GIGANTEA

Solidago gigantea
48 24. Stems hairy throughout or sometimes nearly glabrous toward the base

49 25. Stem leaves below the inflorescence with the blades relatively broad, 2–6 times as long as wide; ray florets 4–8; stems 40–120 cm long but mostly shorter than 100 cm ... 18. S. RADULA

Solidago radula
50 25. Stem leaves below the inflorescence with the blades relatively narrow, 5–13 times as long as wide; ray florets 6–15; stems 30–250 cm long but usually longer than 100 cm (except sometimes in S. altissima var. gilvocanescens and in plants growing in extreme habitats such as railroad cinders)

51 26. Involucre (2.5–)3.0–4.5 mm long; ray florets 10–16, the corolla 3–4 mm long; disc florets 3–7, the corolla 3.0–3.5 mm long ... 1. S. ALTISSIMA

52 26. Involucre 2–3 mm long; ray florets 6–12, the corolla 2–3 mm long; disc florets 2–5, the corolla 2.3–2.7 mm long ... 5. S. CANADENSIS Solidago canadensis
 
 
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