Mikoikoi
Botanical name: Libertia grandiflora
Synonyms: Renealmia grandiflora, Libertia orbicularis
Common name(s): Mikoikoi, mikoikoi iris, native iris, New Zealand iris
About
Libertia grandiflora is a handsome evergreen perennial endemic to New Zealand’s North Island. It forms dense fans of long, narrow, sword-like leaves from short, highly branched rhizomes and produces tall, openly branched flower stems carrying conspicuous white iris-like flowers with bright yellow anthers during spring. Its flowering stems characteristically rise above the foliage, making the floral display particularly prominent. Following flowering, distinctive pear- to teardrop-shaped capsules mature from green to black before splitting open to expose vivid tangerine-orange seeds. Despite its common names, Libertia is not a true Iris, although both genera belong to the iris family, Iridaceae.
Natural habitat
Occurs from coastal to montane environments, particularly in open lowland forest remnants, forest margins, steep slopes, ridgelines, bluffs, cliffs, stream banks and river terraces. It may also occupy relatively dry, sunny banks where competition from taller vegetation is limited.
It is often associated with partially shaded forest margins and broken-canopy environments rather than deep forest interiors, although its broad ecological tolerance allows it to persist across a considerable range of conditions.
Growing environment
Highly adaptable and tolerant of full sun to partial shade. It grows successfully in a wide variety of soils provided they are not permanently waterlogged. Moist, reasonably fertile and free-draining soil generally produces the strongest growth and flowering.
Plants tolerate exposed banks, slopes, frost and periods of seasonal dryness once established. Partial shade is particularly suitable in warmer environments, while plants in cooler districts perform well in more open positions.
Endemic distribution
Endemic to New Zealand and naturally restricted to the North Island, where it occurs from Te Paki in the far north southward to Wellington. It appears to be absent from much of the central Volcanic Plateau.
Older records sometimes extended Libertia grandiflora into the northern South Island, but South Island plants previously included within this species have subsequently been recognised as distinct taxa, particularly Libertia mooreae. True L. grandiflora is therefore regarded as a North Island endemic.
Height
Foliage varies considerably, with leaves approximately 100–1,400 mm long, although many mature plants have leaves around 500–900 mm. Flowering stems commonly reach approximately 0.6–1 m or more and usually extend above the tips of the leaves.
Width
Individual clumps commonly spread approximately 30–80 cm across and can gradually become broader as the short, highly branched rhizomes produce additional closely packed leafy fans.
Flowering
September–November. White flowers approximately 10–30 mm across are carried on tall, broad and openly branched panicles that generally rise above the foliage. Each branch carries approximately 1–6 flowers. Bright yellow anthers contrast strongly with the white tepals.
Fruiting
December–April. Teardrop-shaped capsules approximately 6–14 × 4–8 mm develop after flowering. They are initially green before becoming black at maturity and split fully open, often with the longer valves strongly recurving to expose the bright tangerine-orange seeds.
Uses
Native garden borders
Forest-margin planting
Banks and slopes
Streamside and riparian planting
Rockeries
Mass planting
Underplanting open native woodland
Containers
Native revegetation within its natural range
Erosion-control planting on suitable banks
Feature planting for spring flowers and colourful seed
Appearance
Growth habit: A perennial evergreen herb forming dense, upright clumps of sword-like foliage. Leafy fans are closely crowded on short, extensively branched rhizomes and connected by short stolons. Unlike the far-spreading Libertia cranwelliae, plants remain comparatively compact and develop into increasingly substantial clumps with age.
Leaves: Long, narrow and sword-like, approximately 100–1,400 × 2–12 mm. Both surfaces are similar in appearance, and the leaf bases are characteristically pink-green. Numerous fine longitudinal veins run through the leaves, with the central veins sometimes crowded sufficiently to produce a discernible midrib. Margins are often finely rough or scabrid. In cross-section the leaves are convex and lens-shaped.
Flowers: Approximately 10–30 mm diameter and held on tall, openly branched inflorescences. All tepals are white internally and spread widely. The three outer tepals are comparatively small, narrow, oblong-elliptical and boat-shaped, usually less than half the length of the inner tepals. The three inner tepals are much larger, with broad, almost circular outer portions that may overlap the smaller outer tepals. Their tips are characteristically cleft. The approximately 3 mm long anthers are bright yellow.
Fruit: A small pear- or teardrop-shaped capsule approximately 6–14 × 4–8 mm. Capsules change from green to black as they mature and split fully along their length. The valves can curve strongly backward after opening, prominently displaying the seeds within.
Ecology
Libertia grandiflora is characteristic of relatively open forest, forest margins, bluffs, banks and other habitats where sufficient light reaches ground level. Its dense rhizomatous clumps help occupy and stabilise exposed banks and slopes.
The flowers are insect-pollinated, although the species is also capable of self-pollination. This ability can assist seed production where pollinator activity is limited. The small, lightweight seeds are thought to be dispersed at least partly by wind after the mature capsules split open.
The species is currently regarded as Not Threatened, reflecting its relatively broad North Island distribution and continued occurrence in suitable habitats.
Associated habitats
Occurs within and around lowland and montane native forest, forest remnants, shrubland margins, steep banks, rocky bluffs, cliffs, ridgelines and riparian terraces. It can occur alongside a wide range of native woody plants, including kānuka and tōtara, as well as native grasses, sedges, ferns and other forest-margin herbs.
It is particularly characteristic of transitional environments between closed forest and more open vegetation.
How to grow
An easy and adaptable native perennial deserving wider cultivation. Plant in full sun to partial shade in reasonably fertile, free-draining soil. It tolerates a broad range of garden conditions but should not be planted in permanently waterlogged ground.
Water during establishment, particularly through the first summer. Once established, the dense rhizomatous root system makes plants relatively resilient. Regular irrigation will produce more vigorous foliage in dry gardens, but established plants can tolerate periods of reduced moisture.
Little maintenance is required. Old or damaged leaves can be removed near their bases, and spent flowering stems may be cut back after seed collection. Mature clumps can be divided if they become too large.
For ecological restoration, use appropriately eco-sourced material from within the species’ North Island natural range.
Propagation
Very easily propagated from both fresh seed and division.
Mature capsules can be collected as they darken and begin to split. The conspicuous bright orange seeds can then be removed and sown fresh into a moist, free-draining propagation medium. Fresh seed generally germinates readily.
Division provides a particularly quick method of producing established plants. Mature clumps can be separated into smaller sections, ensuring each division retains healthy roots, rhizome and at least one strong leafy fan. Replant promptly and maintain reliable moisture until new root growth is established.
Cultural use
Mikoikoi is a Māori name associated with New Zealand’s native Libertia. Native iris species were recognised as distinctive components of forest margins, banks and other open habitats. However, specific traditional uses attributed exclusively to Libertia grandiflora are not sufficiently well documented to separate confidently from records referring more generally to mikoikoi or related Libertia species.
Garden value
One of the most attractive and easily cultivated New Zealand Libertia. Its dense architectural foliage provides year-round structure, while the tall flowering stems carry masses of crisp white flowers above the leaves during spring. The bright yellow anthers provide a strong contrast to the petals, and the black mature capsules opening to reveal vivid tangerine-orange seeds provide a second ornamental feature after flowering.
Its tolerance of sun, partial shade, slopes, forest margins and a broad range of soils makes it useful in both formal and naturalistic native gardens. It is particularly effective planted in groups along woodland edges, beneath open native trees, on banks or amongst other low-growing native species where its white spring flowers can rise prominently above the surrounding foliage.