Plumbago

Linnaeus

Sp. Pl. 1: 151. 1753

Gen. Pl. ed. 5, 75. 1754

Common names: Leadwort
Etymology: Latin plumbago, a leadlike ore, alluding to historical use as a cure for lead poisoning
Treatment appears in FNA Volume 5. Treatment on page 610. Mentioned on page 602, 603.
Plants perennial shrubs or suffrutescent herbs; roots not known. Stems erect, prostrate, or climbing, ribbed. Leaves cauline, sessile or short-petiolate (petiole usually less than 1.5 cm); blade elliptic to oblanceolate or spatulate, base narrowed, margins entire, apex acute, acuminate, or obtuse, membranaceous. Inflorescences terminal or axillary spikelike racemes or panicles. Pedicels 2-bracteolate, short. Flowers sometimes heterostylous, short-pedicellate; bracts absent; calyx persistent, 5-ribbed, tubular, with stalked, capitate-glandular protuberances along ribs; lobes triangular, 1–2 mm; corolla salverform, evenly to somewhat unevenly 5-lobed, lobes spreading, obovate, round, or truncate, mucronate; stamens included or exserted, free from corolla; style 1 included or exserted; stigmas 5, linear. Fruits capsules, included, brownish, long-beaked; valves coherent at apex. x = 7.

Distribution

Tropical and subtropical regions, North America, Central America, South America, Europe, Asia, Africa.

Discussion

species 12 (2 in the flora)

Several species of Plumbago are cultivated, including P. auriculata. The entire plant of that species, especially the root, contains plumbagin, a toxic naphthoquinone derivative (oil of plumbago), which may cause severe skin irritation or blistering in humans and may also be toxic to other animals (T. C. Fuller and E. McClintock 1986).

The remarkable glands on the calyces of Plumbago are often called “glandular hairs,” but they are not true hairs, being much more massive and multicellular structures with enlarged, capitate apices.

References

None.

Lower Taxa

Key

1 Corollas pale blue, tube 2 or more times length of calyx; calyces with stipitate, glandlike protuberances and hairs; inflorescences compact, 2.5-3(-5) cm; plants cultivated and locally naturalized in Florida Plumbago auriculata
1 Corollas white, tube mostly less than 2 times length of calyx; calyces with stipitate, glandlike protuberances, true hairs absent; inflorescences elongate, 3-15(-30) cm; plants native Plumbago zeylanica