Convolvulus waitaha, commonly known as grassland convolvulus, is a species of flowering plant in the family Convolvulaceae. A perennial herb, it is endemic to New Zealand. Its range mainly covers the South Island, but it is also sporadically present in the North Island. It is found in various habitats, such as tussock grasslands and pastures. It was first described in a 2003 article in the New Zealand Journal of Botany. Its 2023 assessment in the New Zealand Threat Classification System was "Not Threatened".
Description Convolvulus waitaha is a perennial herb in the family Convolvulaceae. The stems can reach a length of up to , which may be covered with hairs. Leaves are found in a rosette arrangement. Leaves are arranged alternately on the stems and measure 6–17 × 5–12 mm long. They range from triangular to oval or broadly oblong in shape and are green in colour. The leaf surface is usually smooth. Leaf edges are smooth to slightly wavy.
The pedecils are 8–18 mm long. The sepals are 3.6–4 × 2.1–2.6 mm long. The flowers are white, about 10–16 mm wide when open. The centre of the petals is pale green. The fruits are found in seed capsules which are 5–6 × 5–6.5 mm long, and contain two to four seeds. The seeds are 3.1–3.9 × 2.3–3.3 mm long, and brown to greyish in colour. C. waitaha has a diploid chromosome count of 22.
Taxonomy The genus Convolvulus was established by the European botanist Carl Linnaeus in 1753. C. waitaha was first described in a 2003 article in the New Zealand Journal of Botany by the botanists Peter Brian Heenan, Brian Molloy, and Peter de Lange. The species was previously treated as a subspecies of Convolvulus verecundus. There are 227 species of the genus Convolvulus currently accepted by the Plants of the World Online taxonomic database. The genus has a worldwide distribution. A monograph of the genus was conducted in 2015. Nepomuceno et al. (2025) combined the genus Calystegia to Convolvulus.
Etymology The etymology (word origin) of C. waitahas genus name, Convolvulus, comes from the Latin , meaning "to twine around". The specific epithet (second part of the scientific name), waitaha, is a Māori language word meaning 'backwater'. It comes from , meaning 'water', and 'taha', meaning "to pass to one side". The species is commonly known as grass convolvulus.
Distribution Convolvulus waitaha is endemic to New Zealand. Its range sporadically covers the eastern North Island and South Island. There is a historical record of the plant being present in Hawke's Bay. C. waitaha is found in numerous localities along the Cook Strait. In the South Island, C. waitaha is found from the Marlborough Region south to Otago. Its 2023 assessment in the New Zealand Threat Classification System was "Not Threatened".
Habitat Convolvulus waitaha is found in coastal to lowland environments, reaching above sea level at maximum elevation. It is found in various habitats, including tussock grasslands, browsed pastures, banks, rocky slopes, and gravelly areas.
Ecology The members of the Convolvulaceae are primarily pollinated by insects. The seeds of C. waitaha are dispersed by the wind.
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