Plumbago

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.

Selected References

None.

Lower Taxa

Plumbago auriculata, Plumbago zeylanica

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