Baccharis neglecta Britt., Roosevelt weed, linear–leaved false willow. Shrub, winter–deciduous, several—many–stemmed at base, having ascending principal axes and ascending to spreading current–year branches, in canopy flowering twigs ascending from each node of principal axes, flowering specimens with sprays of small white heads 150—450 cm tall; dioecious; shoots with only cauline leaves, glabrous, shoots glossy with resin on growing leaves and elongating stems with glands in shallow pits, young shoots aging encrusted with some dried resin, foliage not scented.
Stems on young shoots mostly 6–ridged, ca. 1 mm in diameter, with 3 ridges descending from each leaf, tough, internodes mostly 3— < 15 mm long, at node having a small swelling at top of each leaf base, green; older stems forming brownish periderm; bark on woody axes splitting and furrowed and yellowish brown weathering paler.
Leaves helically alternate, simple, short–petiolate to sessile, without stipules; petiole indistinct from blade, shallowly channeled, < 3 mm long, 1–veined with midvein raised on lower side; blade linear to elliptic–linear or oblanceolate–linear and straight to slightly curved, 15—70(—80) × 1.5—5(—10) mm, the wider leaves only on principal lower, vigorous vegetative shoots and somewhat asymmetric by blade being wider on 1 side of midrib, long–tapered at base, low–serrate to entire having teeth mostly absent below midblade and < 10 teeth per blade, acute at tip, 1(3)–veined at base with midrib raised on lower surface.
Inflorescences unisexual heads, in terminal, open, paniclelike arrays at ends of branches, terminal branchlets with several heads, head discoid, 2 mm across, in range with 10—15 staminate flowers or 15—20 pistillate flowers, mildly scented, bracteate, glabrous, resinous but not conspicuously so; bract subtending lateral branch and branchlet leaflike, to 15 × 1—1.4 mm, decreasing upward, entire; axes ridged with 3 ridges descending from each bract; bract subtending peduncle < 1—4 mm long, obtuse at tip; peduncle at anthesis short—4 mm long (staminate) and 1—6 mm long (pistillate), with 1—2 grooves, having 3—4 bracts along axis approaching head; involucre bell–shaped, 3.5—4 × 2—2.3 mm (staminate) and lanceoloid, 4.5—5 × 2 mm (pistillate), phyllaries 20—26 in 3—5 series, appressed, unequal, ovate to lanceolate, < 1 mm long (outer phyllaries) to 2—4 × 0.8—1 mm, scarious with membranous margins and exposed portion yellowish green to green and slightly resinous, the tip and margins somewhat fringed above midpoint; receptacle flat to slightly domed, without bractlets (paleae), shallowly pitted, low rim surrounding each ovary with white, glandlike hairs.
Staminate flower structurally bisexual, radial, ca. 1.5 mm diameter; calyx (pappus) of ca. 30 capillary bristles in 1 whorl, ca. 2.5 mm long, white, often with kinky hairs at base, with short branches (short–plumose) above midpoint; pappus slightly surpassing involucre and compacted on head surface (not erect); corolla 5–lobed, ca. 3 mm long; tube + throat somewhat expanded in throat, throat > tube, pale green, glabrous; lobes lanceolate aging somewhat recurved, ca. 1.2 × 0.3—0.35 mm, white; stamens 5, filaments fused to corolla above tube, with anthers becoming almost completely exserted and visible above involucre and pappus; filaments in bud 0.6 mm long increasing during pollination, white; anthers fused into cylinder surrounding style, basifixed, dithecal, ± 1.3 mm long including appendages at tip, pale yellow, the colorless appendages acuminate, 0.3—0.4 mm long, longitudinally dehiscent; pollen pale yellow; pistil 1; ovary inferior, aborted, wedge–shaped, ca. 0.3 mm long; style exserted during pollination with stigma exserted above and spreading anther appendages, nectary swollen at base, 0.3 mm long, green, style unbranched, pale green at base to whitish above, the stigma terminal and somewhat club–shaped, 0.5 mm long, white and conspicuously papillate–hairy.
Pistillate flower structurally unisexual, < 0.5 mm across; calyx (pappus) of ca. 30 capillary bristles in 1 whorl arising from green rim atop ovary, at anthesis surpassing involucre and ca. 4 mm long increasing 2× in fruit, more slender than staminate pappus and not short–plumose, white; corolla irregularly short–toothed, narrowly cylindric, 2.5—3.3 mm long, gradually tapered base to tip, pale green at base to whitish above, glabrous; stamens absent; pistil 1; ovary inferior, columnar and weakly 5–sided, 0.65—0.7 × 0.25—0.3 mm, white, inconspicuously 10–striped (= ribs), lacking glandular hairs, 1–chambered with 1 ovule; style exserted (with and often above pappus), 4.5—5.5 mm long, nectary at base, short, greenish, style 2–branched, greenish at base to white above, the branches fully exserted, divergent, slender, 0.8—1 mm long, white, inconspicuously papillate
Fruits cypselae, columnar, 1—1.5 mm long, cinnamon brown, 10–ribbed, glabrous; pappus of ca. 30 capillary bristles of various length, 5—8 mm long, white.
A. C. Gibson