Leptinella is a genus of prostrate or low-growing flowering plants in the family Asteraceae (order Asterales), comprising around 33 species distributed across New Zealand, Australia, New Guinea, South Africa, and South America. The genus is particularly diverse in New Zealand, where approximately 24 species are endemic.
Plants are perennial herbs (rarely facultatively annual), typically prostrate in habit, with axillary peduncles that are nude or bear one to several reduced bracts. The flowerheads may be bisexual — containing both pistillate and staminate florets in varying proportions — or wholly unisexual. The most distinctive morphological feature of the genus is the corolla of the pistillate florets: it is tubular and conical to cylindric, persistent or deciduous, and uniquely inflated, with a hollow space between its outer surface and an inner layer that closely surrounds the style. This inflated female corolla is the character that, combined with chromosome numbers based on x = 26, distinguishes Leptinella from the closely related genus Cotula and from other members of tribe Anthemideae. Disk florets are seed-sterile and functionally staminate, with the style apex forming an undivided, slightly concave disc. Achenes are thick, not flattened, convex on the dorsal surface, and lack wings, though they bear an obvious or obscure margin.
Leptinella was first described by the botanist Cassini in 1822, with Leptinella scariosa Cass. as the type species. For more than a century, these plants were subsumed within the genus Cotula, until Lloyd & Webb reinstated Leptinella at generic rank in 1987, following Lloyd's comprehensive 1972 revision of the NZ, subantarctic, and South American species. One cultivated selection, Leptinella squalida 'Platt's Black', has gained popularity in horticulture as a low-growing ground cover and as a component of tapestry lawns.
Etymology
The genus name Leptinella was coined by the French botanist Henri Cassini and published in 1822 in the Bulletin des Sciences, de la Société Philomatique de Paris (ser. 3, 9: 127–129). The type taxon is Leptinella scariosa Cass.
Distribution
Leptinella is centred on New Zealand, where approximately 24 species are endemic and one further species is indigenous but not endemic, giving around 25 species in the archipelago. Beyond New Zealand the genus extends to Australia, New Guinea, South Africa, and South America. Many alpine and subalpine habitats in New Zealand support multiple Leptinella species.
Taxonomy Notes
Leptinella was described by Cassini in 1822 but was subsequently lumped into Cotula for over a century. Lloyd's 1972 revision of the NZ, subantarctic, and South American species of Cotula section Leptinella laid the groundwork for recognising the group at genus level. Lloyd & Webb formally reinstated Leptinella as a distinct genus in 1987 (New Zealand Journal of Botany 25: 99–105), on the basis of the inflated pistillate corolla and chromosome base number x = 26, characters absent from the remaining sections of Cotula and from other Anthemideae.
Cultivation
Leptinella squalida 'Platt's Black', a dark-leaved cultivar, is the species most widely grown as a garden plant. It is valued as a dense, mat-forming ground cover and is used as an ingredient in tapestry lawns, where its fine, ferny foliage and tolerance of light foot traffic make it a useful low-growing filler between other creeping plants.
