Sambucus nigra subsp. canadensis (l.) Bolli, common elderberry, American elderberry. Robust shrub (small tree), winter–deciduous, several—many–stemmed at base, in range flowering specimens 150—400+ cm tall; shoots with only cauline leaves, essentially glabrous with inconspicuous short hairs on foliage. (l.) Bolli, common elderberry, American elderberry. Robust shrub (small tree), winter–deciduous, several—many–stemmed at base, in range flowering specimens 150—400+ cm tall; shoots with only cauline leaves, essentially glabrous with inconspicuous short hairs on foliage.
Stems becoming ± 12–ridged, with several ridges descending from each leaf, sometimes purplish red just above node, having long internodes especially on robust, rapid–growing shoots; pith wide, white, soft.
Leaves opposite decussate, odd–1—2–pinnately compound, with 2—4 pairs of primary lateral leaflets, on robust shoots commonly having leaf or leaves with 1—4 lateral primary leaflets having 2—3 secondary leaflets, petiolate, without stipules (in 2–compound leaves, linear, vestigial leaflets at base of petiolate appear to be stipels); petiole shallowly channeled, 55—110 mm long, channels of leaf axis puberulent; rachis groove–channeled, to 175 mm long and often 2× petiole, with petiolules arising from ridges, lateral leaflets usually opposite and pairs spaced < 20—65 mm apart, when 2–compound primary leaflet lower pairs with 1—2 smaller leaflets arising just beneath dominant terminal secondary leaflet; petiolules of primary leaflets channeled, to 16 mm long (of terminal leaflet to 20 mm long), channel puberulent; blades of leaflets ovate–elliptic or ovate–oblong to ovate or elliptic–obovate (terminal leaflet), < 45—165 × 16—83 mm, broadly tapered and slightly oblique (longer on trailing edge) to subtruncate at base, low–serrate on margins with teeth mostly pointed but occasionally broader and blunt, ± acuminate at tip, pinnately veined with principal veins ± sunken and puberulent on upper surface and principal veins raised on lower surface, upper surface aging glossy glabrescent, lower surface with inconspicuous glandular hairs along midrib and short–hairy on blade tissue.
Inflorescence panicle of cymes, terminal, flat–topped to domed, 75—384 mm across with 100—4000+ flowers, compound with 4 primary rays (at top of peduncle) opposite decussate (lacking internode) + 1 terminal central ray (= 5–forked), node 2 usually radially 5–forked, but subsequent nodes with unequal rays and oriented away from lower side, 2—7 nodes 5–forked, axes decreasing upward to ultimate flower clusters; peduncle ridged, often 100+ mm long on robust shoots; bract subtending each ray at forks awl–shaped, < 0.5 mm long, mostly nongreen, with short hairs; minor axes often sparsely puberulent, at and around fork papillate to glandular–hairy and some hairs turning red; bractlet subtending pedicel = diminutive bract; pedicel cylindric, 1.3—4.3 mm long, white, sparsely papillate, persistent.
Flower bisexual, radial with parts in sets of 4—5, 5—6.3 mm across, never closing, mildly fragrant; calyx 4—5–lobed, whitish; tube < 0.3 mm long; lobes spreading, equal, triangular, 0.6—0.7 mm long, minutely toothed above midpoint, ascending after corolla abscised; corolla 4—5–lobed, dishlike (rotate), white, easily dislodged; tube 0.35—0.5 mm long, orifice 0.7—1.1 mm across; lobes overlapping in bud and at anthesis, spreading and cupped upward slightly, broadly ovate to roundish, 1.9—2.2 × 1.5—1.9 mm, rounded to obtuse at tip; stamens 4—5, fused to corolla tube just below sinuses (alternate with corolla lobes); filaments spreading, 1.5—1.9 mm long, white; anthers basifixed (filament fused to base of anther but continuous with connective), dithecal, 0.6—0.8 mm long, cream–colored, surfaces with domed cells, longitudinally dehiscent; pollen white; pistil 1, ca. 2 mm long; ovary half–inferior, overall ellipsoid, above calyx ovoid to conic, 0.7—0.8 × 0.8—0.9 mm, white, 3—5–chambered, each chamber with 1 pendent ovule; styles 3—5, ascending in a ring with depression in center, short; stigmas appressed to surface of ovary, 0.4 mm long, conspicuously papillate.
Fruit drupe, with 3—5 stones, oblate spheroid, 4.3—5.2 × 5—6.2 mm, glossy black (not glaucous), with 4—5 calyx lobes persistent and appressed to top of fruit; pulp (mesocarp) fleshy, watery, purplish, not sweet; stone (endocarp) 3—5–parted, very hard, each part 3–sided with 2 flat faces and rounded on back, 2.2—3.2 mm long, dull amber, rough cobblestonelike to ± transversely wrinkled on all faces.
A. C. Gibson