1. Syringa vulgaris L. (common lilac)

Pl. 460 g; Map 2106

Plants shrubs, 1.5–3.0(–7.0) m tall. Trunks few to several, ascending, the bark grayish brown to more commonly gray, thin, relatively smooth, but with raised leaf scars and lenticels. Twigs relatively stout, reddish brown to dark brown, with a pale, waxy coat, tending to peel in strips with age, glabrous, more or less 4-angled in cross-section (usually with 4 slender ridges), the leaf scars raised and the lenticels conspicuous and raised. Terminal buds usually absent, suppressed by an apical pair of relatively large axillary buds, these ovoid to broadly ovoid, with scales that are broadly but sharply pointed at the tips (those lower on the twigs similar, but smaller). Leaves opposite, moderately to long-petiolate, the petioles of the largest leaves 19–30 mm long. Leaf blades simple, 3–10 cm long, 1–6 cm wide, ovate, tapered to the sharply pointed tip, broadly rounded to truncate or shallowly cordate at the base, the margins entire, the upper surface green to dark green, glabrous, the undersurface lighter green, glabrous. Inflorescences terminal (often paired), many-flowered, ascending to spreading or drooping panicles 8–20 cm long developing with or after the leaves, the lower branch points with small, leaflike or scalelike bracts, the flowers with slender stalks 1–4 mm long, strongly fragrant. Calyces shallowly 4-lobed, 1.5–2.2 mm long, the lobes narrowly triangular to triangular, often toothlike. Corollas 4-lobed to slightly above the midpoint, 9–16 mm long, trumpet-shaped, the lobes oblong to oblong-elliptic, purple to bluish lavender, pale lavender, or rarely white. Style 1.5–2.5 mm long, with a pair of ascending branches at the tip. Fruits capsules, 10–18 mm long, slightly flattened, not winged, oblanceolate to narrowly obovate in outline, beaked at the tip, brown, glabrous, often somewhat shiny, dehiscing longitudinally. Seeds 10–14 mm long, flattened, narrowly winged toward the midpoint, tapered at each end, brown. 2n=44–48. April–June.

Introduced, uncommon in the eastern half of the state (native of Europe; introduced sporadically nearly throughout the U.S., Canada). Edges of mesic upland forests; also old homesites, railroads, and roadsides.

This species frequently persists for long periods of time at abandoned farmsteads, but in Missouri it rarely reproduces itself. Lilac is cultivated for its showy flowers with their characteristic, strong, sweet fragrance. A very large number of cultivars exists, varying in flower color, flower structure (single and double flowers), growth form, and disease resistance. Lilac fragrance, which is composed of a mixture of furanoterpenoid derivatives, is sold as an essential oil and is used extensively in perfumes, soaps, bath products, scented candles, and potpourri.