2. Solidago arguta Aiton
Pl. 239 a, b;
Map 991
Plants with the
rootstock short, stout, sometimes horizontal, branched or with offsets. Stems 1
or occasionally few, 40–120 cm long, erect or ascending, with several fine,
longitudinal ridges or grooves but not noticeably angled, glabrous below the
inflorescence or sparsely to moderately pubescent with spreading and/or curved
hairs, not or only slightly shiny, not glaucous. Leaves basally disposed and
usually persistent at flowering (additional rosettes usually present adjacent
to the flowering stem). Basal and lowermost stem leaves with the blade 8–30 cm
long, 4–10 cm wide, mostly 2–4 times as long as wide, broadly ovate to broadly
elliptic, somewhat thickened, tapered fairly abruptly to the winged petiole at
the base, rounded or more commonly tapered to a bluntly or sharply pointed tip,
the margins finely to coarsely and sharply toothed, microscopically roughened,
the upper surface glabrous or slightly to moderately roughened with
forward-angled minute, stiff, stout hairs lacking a pustular base, the
undersurface glabrous or moderately pubescent with mostly spreading hairs, with
1 main vein, the fine, pinnate secondary veins easily observed (these usually
forming an irregular network). Median and upper stem leaves 1–8 cm long,
lanceolate to elliptic or oblanceolate, sessile or short-petiolate, otherwise
similar to the lower stem leaves. Inflorescences relatively dense and narrow to
more commonly open and broad, pyramidal panicles (the lower branches sometimes
elongate), the longer branches and occasionally also the tip usually somewhat arched
or nodding, the heads oriented upward along the branches. Involucre 4–6 mm
long, the bracts in 3–5 unequal series. Involucral bracts oblong-ovate to
narrowly oblong and mostly rounded to bluntly pointed at the
appressed-ascending tip (those of the outer series sometimes sharply pointed),
the thin, white to yellowish white margins hairy, the outer surface glabrous,
with a poorly differentiated green to light green central region mostly above
the midpoint, this tapered gradually or not at all to the midvein, the midvein
not or only slightly thickened, and no additional veins present. Receptacle
naked. Ray florets 2–8, the corollas 4–6 mm long, yellow. Disc florets 8–20,
the corollas 3.5–4.0 mm long, the lobes 0.5–1.5 mm long, yellow. Pappus 3.0–3.5
mm long, some of the bristles slightly thickened toward the tip. Fruits 1.5–2.0
mm long, narrowly obovoid, glabrous or finely hairy. 2n=18, 36. June–October.
Scattered in the
Ozark and Ozark Border Divisions (eastern U.S. west to Illinois and Texas;
Canada). Mesic to dry upland forests, glades, ledges and bases of bluffs, banks
of streams and rivers, and occasionally bottomland forests.
Steyermark
(1963) noted that this attractive species is a desirable addition to the
wildflower garden. The taxonomy and nomenclature of the S. arguta group
are complex and still not fully understood. Steyermark (1963) based his
treatment of the group on extensive field and herbarium studies in the state,
concluding that four elements could be recognized in Missouri, which he treated
as varieties. Morton (1974) summarized and amended the taxonomic and
nomenclatural conclusions developed in his doctoral research (Morton, 1973),
which involved intensive field and herbarium studies across the range of the
complex. He argued that the rare S. arguta var. neurolepis
(Fernald) Steyerm. (described from plants collected at Oronogo, Jasper County,
but also known from St. Francois County and to be expected elsewhere) actually
represents a putative hybrid between S. arguta and S. ulmifolia,
which he called S. Hneurolepis Fernald. Morton (1973, 1974) also
examined the type specimen of S. boottii Hook. and concluded that this
name had been misapplied. Steyermark (1963) and others had applied this name to
plants with glabrous leaves and called plants with the leaf undersurface hairy S.
arguta var. strigosa. However, the type specimen of S. boottii
is a hairy-leaved plant, and the oldest name for this pubescent phase is var. boottii.
The next oldest name for the glabrous-leaved plants that Steyermark called var.
boottii is S. arguta var. caroliniana. According to Morton
(1973), the epithet S. strigosa actually applies to a southeastern
species, S. ludoviciana (A. Gray) Small, which does not occur in
Missouri. Other infraspecific taxa recognized by Morton do not occur in
Missouri. His taxonomy and nomenclature were adapted by Cronquist (1980) and
Gleason and Cronquist (1991), whose treatments are followed here. The
differences between the Missouri varieties are summarized in the key below.
Note that vegetative material or plants in early flower cannot be determined
satisfactorily below the species level in most cases.