Codon royenii

L.
Family: Boraginaceae
Common names: honey bush (Eng.); heuningbos, suikerkelk (Afr.)

Codon royenii

A prickly, hairy annual or multiseasonal herb characterized by flowers with a white, tubular corolla, with reddish brown or occasionally greenish yellow veins on the outside of the tube, sometimes with red dots on the lobes.

Description
Codon royenii is a spreading to erect, annual or multiseasonal herb, up to 1.3 m high. It is characterized by stems and leaves prickly pubescent with spine-like, white or dull yellowish hairs, which are up to 10 mm long. The leaves are stalked (petiolate) with petioles up to 40 mm long. The leaf blade is ovate or ovate-lanceolate, diminishing in size towards the inflorescence, with an obtuse to wedge-shaped (cuneate) base, acute apex and an entire or sinuate-dentate margin.

Flowers are borne in terminal inflorescences from April to September, flower stalks (pedicels) short, calyx with 10 or 12 lobes only fused at base; lobes linear ± 15-20 mm long alternate ones nearly as long as corolla, others slightly shorter, densely hairy and corolla deeply cup-shaped, white with reddish brown veins, sometimes with red dots (lenticel-like protuberances) on lobes, tube cylindric, 20-25 mm long, lobes 10 or 12, shorter than tube, oblong or ovate-elliptic, 5-10 mm long. The species also has 10 or 12 stamens at the base of the corolla, sometimes slightly exceeding it, hirsute filaments, versatile anthers and a persistent style almost as long as the corolla, linear, cleft to almost halfway with simple stigmas.

Fruit: is a 2-valved capsule with scattered dark red dots (lenticel-like protuberances) with fruit stalks up to 15 mm long, many-seeded with seeds globose or irregularly angled and wrinkled (rugose).

Conservation Status
Codon royenii is not regarded as a threatened plant species.

Map showing distribution

Distribution and Habitat
Codon royenii occurs in semidesert and desert parts of Namibia, Northern and the Western Cape. The core distribution area of C. royenii coincides with the winter rainfall Succulent Karoo Region (Van Wyk & Smith 2001), with short extensions into adjacent parts of Namibia and the Northern Cape, areas that receive mainly summer or all-season rainfall. It inhabits sandy flats, dry, sandy river beds, rocky slopes, pockets of gravel between boulders, disturbed places or also occurs along roadsides.

Grows in dry areas

Derivation of name and historical aspects
The genus Codon was established by Linnaeus in 1767. The generic name alludes to the Greek word kodon, a bell (although the flowers do not hang down) and refers to the shape of the flowers of C. royenii which are deeply cup-shaped. C. royenii is named after either David or Adriaan van Royen or both, Dutchmen who associated with Carl Linnaeus during the latter's years in Holland. This striking genus, characterized by prominent white or dull yellowish 'thorns', comprises two species (and possibly a third species), C. royenii L. and C . schenckii Schinz, both endemic to Namibia and South Africa . The genus Codon has traditionally been assigned to the family Hydrophyllaceae, where it seems to be unusual geographically, as the family is otherwise largely restricted to the New World. Similarities in pollen and macromorphological characters between Codon and other members of Boraginaceae indicate that Codon should be placed in a subfamily within Boraginaceae s.l. A subfamily, Codonoideae, was established to accommodate this southern African genus in the Boraginaceae (Retief & Van Wyk 2005).

Ecology
During the course of research on the wasps and bees of semi-arid areas, Sarah and Fred Gess, two eminent entomologists, observed that what appears at first glance to be the bottom of a C. royenii flower is in fact tightly appressed, hairy staminal filaments curving inwards from the cup walls at 5 mm above the true bottom of the flower. Above this level, the filaments separate and rise upwards and outwards to hold the anthers erect. The flowers are most often visited by a black carpenter bee with rufous legs- Xylocopa lugubris (Apidae: Anthophorinae) and two species of pollen wasps (Vespidae: Masarinae).

The robust carpenter bee flies straight into the flowers with its underside towards the centre of the flower. In doing so it makes contact with the anthers when in the pollen presenting phase, and with the stigmas when in the receptive phase-the perfect pollinator for these flowers. Xylocopa lugubris , which nests in dry, pithy stems, usually of Aloe inflorescences, is widespread in Africa and is therefore available throughout the range of C. royenii.

Unlike the carpenter bee, the two relatively small pollen wasps are not very reliable pollinators as they often drink nectar from a flower without making contact with the anthers or stigmas. The wasps were observed using the flowers of C . royenii also as a shelter for sunning themselves, especially during cool, breezy weather, as well as for courting and mating!

Uses and cultural aspects
Because of its copious nectar (which explains its common name, honey bush), the flowers of Codon royenii are collected by the Nama people as a delicacy (Gess 1999). The predominantly spiny habit may protect the plants against browsing by animals in the very dry areas of southern Africa where they occur. Plants of C. royenii are nonetheless eaten by stock when the plants are young.

Growing Codon royenii

Codon royenii is not grown horticulturally. The attractive flowers of this species present a challenge to the keen gardener!

References and further reading

  • Gess, S. 1999. Codon flowers: chalices of hidden nectar. Veld & Flora 85: 30, 31.
  • Retief, E. & Van Wyk, A.E. 2005. Codonoideae, a new subfamily based on Codon (Boraginaceae). Bothalia 35: 78, 79.
  • Retief, E., Van Wyk, A.E. & Condy, G. 2005. Codon royenii. Flowering Plants of Africa 59: 114-121.
  • Van Wyk, A.E. & Smith , G.F. 2001. Regions of floristic endemism in southern Africa : a review with emphasis on succulents. Umdaus Press, Pretoria.

 

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National Herbarium
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