Codon is a small genus of flowering plants in the family Codonaceae (or Boraginaceae, depending on the taxonomic authority) within the order Boraginales. It is the only genus in its family and contains just two accepted species, both native to southern Africa — specifically the Cape Provinces of South Africa and Namibia. The genus was described by Carl Linnaeus.
Codon species are annual to perennial herbs that grow from strong taproots. The entire plant body is densely covered with strong, mineralised, unicellular trichomes borne on cystolithic foot-cells — a distinctive anatomical feature. The flowers are tetracyclic and polymerous, with whorl counts ranging from 10 to 20 parts (most commonly 12-merous), showing considerable variability even within a single individual. The sepals are free, while the petals are fused for up to three-quarters of their length. The filament bases are fused with the corolla base, and the fused portions form septa that create separate nectar chambers. A lobed nectary disc sits at the base of the superior gynoecium, with each lobe covered in nectarostomata that secrete nectar into the chambers. The gynoecium consists of two carpels. Flowers are bell-shaped and white in Codon royenii and saucer-shaped and yellow in Codon schenckii. The fruit is an apical-loculicidal capsule, and the seeds have a reticulate surface sculpture.
Taxonomically, Codon has been shuffled between families: it was historically placed in Hydrophyllaceae and later Boraginaceae, but a 2014 phylogenetic study resolved it as sister to Wellstediaceae + Boraginaceae sensu stricto, leading to the proposal of the separate family Codonaceae. As of late 2025, most taxonomic sources accept Codonaceae, though Plants of the World Online continues to retain it within Boraginaceae. The common name for the genus is "nectarcups."
Taxonomy
Codon has a contested family placement. It was historically classified under Hydrophyllaceae and later Boraginaceae. A 2014 phylogenetic analysis (Weigend & Hilger) placed it as sister to Wellstediaceae and Boraginaceae sensu stricto, and the new family Codonaceae was proposed, with Codon as its sole genus. As of December 2025, most taxonomic authorities accept Codonaceae, but Plants of the World Online (POWO) retains the genus within Boraginaceae. GBIF also lists it under Boraginaceae. The genus authority is Linnaeus (L.).
Distribution
Both species of Codon are native to southern Africa, with their range limited to the Cape Provinces of South Africa and Namibia. The genus is endemic to this region.
