5. Helianthus grosseserratus M. Martens (sawtooth sunflower)
H.
grosseserratus ssp. maximus
R.W. Long
Pl. 280 e, f;
Map 1192
Plants perennial
herbs, with short-creeping or sometimes longer, thick, branched rhizomes,
sometimes occurring as dense colonies of stems. Stems often appearing somewhat
clumped, 50–300 cm long, glabrous below the midpoint, often sparsely to
moderately pubescent with short, ascending hairs toward the tip, often somewhat
glaucous. Leaves relatively numerous and well developed along the stem (usually
with 20–25 nodes), mostly alternate or occasionally most of the leaves opposite
and only the uppermost ones alternate, all or nearly all short-petiolate.
Blades of the stem leaves 5–30 cm long, 1–9 cm wide, narrowly lanceolate to
narrowly ovate (mostly 5–10 times as long as wide), flat or only shallowly
concave, not folded longitudinally, tapered at the base, tapered to a sharply
pointed tip, the margins finely to coarsely and sharply toothed (rarely
entire), flat, the upper surface sparsely to moderately pubescent with minute,
broad-based hairs, usually not or only slightly roughened to the touch, the
undersurface densely pubescent with minute, soft, appressed hairs, both
surfaces also with sparse to moderate, sessile, yellow glands, more or less
with 1 main vein but the lowermost pair of lateral veins usually slightly more
prominent than the other pinnate lateral veins. Inflorescences of solitary
terminal heads or more commonly appearing as open clusters or open panicles.
Involucre 10–15 mm long, 15–25 mm in diameter, mostly extending slightly beyond
the tips of the disc corollas, the bracts in 2 or 3 subequal series, narrowly
lanceolate to nearly linear, tapered to a sharply pointed, slender, loosely
ascending to more commonly spreading or recurved tip, the margins with short,
ascending to occasionally spreading hairs, at least toward the base, the outer
surface glabrous or sparsely hairy toward the base but usually lacking glands.
Receptacle convex, the chaffy bracts 7–9 mm long, narrowly oblong-triangular to
nearly linear, angled or short-tapered to a sharply pointed, green, minutely
hairy tip, the outer surface also minutely hairy. Ray florets 10–25, the
corolla 2.0–4.5 cm long, glabrous. Disc florets with the corolla 5–6 mm long,
yellow throughout. Pappus of 2 scales 2.0–2.5 mm long, these narrowly
triangular, tapered abruptly to a sharply pointed, often minutely awnlike tip.
Fruits 3–4 mm long, narrowly wedge-shaped, flattened but more or less 4-angled
in cross-section, the surface glabrous, often finely mottled with dark brown to
nearly black and lighter brown patches. 2n=34. July–October.
Scattered in the
Glaciated and Unglaciated Plains Divisions and the western portion of the Ozark
and Ozark Border Divisions; absent from most of the southeastern quarter of the
state (eastern U.S. west to North Dakota and Texas; Canada; introduced
sporadically in the northwestern U.S.). Bottomland and upland prairies; bases
of bluffs, banks of streams and rivers, fens, and margins of ponds and lakes;
also ditches, margins of cultivated fields, pastures, railroads, roadsides, and
open, disturbed areas.
Rarely collected
plants with most of the disc florets converted to rays have been called f. pleniflorus
Wadmond. It is not clear whether this represents some form of genetic mutation
or a symptom of a disease. Steyermark (1963) noted that hybrids have been
recorded between H. grosseserratus and H. maximilianii (H.
×intermedius R.W. Long) in adjacent states and should be searched for in
Missouri. Thus far a single collection made by B. F. Bush in 1916 in Jackson
County (and labeled as introduced there) appears to represent this hybrid.