1. Melissa officinalis L. var. officinalis (lemon balm, bee balm)

Pl. 436 c, d; Map 1962

Plants perennial herbs, with rhizomes. Stems 30–100 cm long, erect to loosely ascending, often from a spreading base, sharply 4-angled, several-branched, densely pubescent with short, spreading, gland-tipped hairs and sparser, longer, nonglandular hairs (rarely nearly glabrous). Leaves opposite, the lower and often also median stem leaves long-petiolate, those of the inflorescence short-petiolate, the petioles unwinged, with a pleasant, lemony odor when bruised or crushed. Leaf blades 1–7 cm long, the transition from vegetative stems to inflorescences fairly abrupt, those in the inflorescences noticably smaller (1–3 cm) than the vegetative stem leaves (the largest 4–7 cm), heart-shaped or more commonly broadly ovate to triangular-ovate or elliptic, unlobed, the margins bluntly to sharply toothed, cordate to more commonly truncate or broadly angled at the base, angled to a bluntly or sharply pointed tip, the upper surface sparsely pubescent with relatively long, mostly multicellular hairs, the undersurface usually densely pubescent with minute, spreading, mostly gland-tipped hairs, sometimes also sparsely to moderately pubescent with long, fine, spreading hairs, also with usually conspicuous sessile glands. Inflorescences axillary, dense clusters of 4–14 flowers per node, these short-stalked. Bractlets 2–3 mm long, shorter than the calyces, linear to ovate, sharply pointed but not spinescent. Calyces 7–9 mm long, strongly zygomorphic, lacking a lateral projection, symmetric at the base, more or less bell-shaped, the tube strongly 13-nerved, glabrous in the mouth, the lips about 65% as long as the tube, the upper lip arched upward, with 3 shallow, broadly triangular lobes (teeth), the lower lip slightly arched upward, with 2 deeper, narrowly triangular lobes, the lobes all tapered to sharply pointed, slightly spinescent tips, sparsely to densely pubescent with minute, spreading, mostly gland-tipped hairs on the outer surface, also with sparse to moderate, long, spreading, nonglandular hairs, becoming somewhat enlarged and papery at fruiting. Corollas 8–15 mm long, zygomorphic, pale yellow, lacking darker purple spots, fading to white or pinkish-tinged, the outer surface moderately pubescent, with short, fine, spreading hairs, the tube funnelform and somewhat arched, densely glandular-hairy in the throat, the lobes shorter than the tube, the upper lip slightly hooded but spreading at the tip, shallowly to moderately 2-lobed, the lower lip with the central lobe broader than the 2 lateral lobes. Stamens 4, not exserted (ascending under the upper lip), the lower pair somewhat longer than the upper pair, the anthers small, the connective short, the pollen sacs 2, spreading, white or yellow. Ovary deeply lobed, the style appearing more or less basal from a deep apical notch. Style not exserted, with 2 slightly unequal branches at the tip. Fruits dry schizocarps, separating into usually 4 nutlets, these 1.5–2.0 mm long, oblong-obovoid to ellipsoid, rounded at the tip, the surface yellowish brown to greenish brown or dark brown, finely pebbled or finely pitted, glabrous. 2n=32. June–September.

Introduced, uncommon, widely scattered, mostly in the southern half of the state (native of Europe; introduced sporadically in the U.S., Canada). Openings of mesic upland forests and banks of streams; also fencerows, old homesites, gardens, railroads, roadsides, and disturbed areas.

This species is cultivated for its pleasantly scented foliage, which is used in fragrances, potpourri, massage oils, and in liquors. It has also been used medicinally as a mild sedative and for hypertension. More recently there has been interest in its possible memory-enhancing properties as an adjunct treatment for the early stages of Alzheimer’s Disease (S. Schwartz, 2005). Beekeepers sometimes have used M. officinalis to attract swarms of bees to new hives, as terpenoids in the essential oil are the same compounds as the natural pheromones produced in the Nasonov glands of honeybees (Mabberley, 1997).

The other subspecies, ssp. altissima (Sm.) Arcang., is endemic to portions of southern Europe. It is not cultivated and has not been introduced into North America. This tetraploid (2n=64) differs from ssp. officinalis in being densely white- to gray-woolly and has some of the upper leaves truncate (vs. angled) at the base, as well as differing slightly in the shape of the calyx lobes.