Astelia chathamica aka Chatham Islands Kakaha

Astelia chathamica forms dense clumps of sword-shaped silvery foliage, typically reaching 1-1.5 metres (3-5 feet) in height with a spread of 0.5-1 metre (1.5-3 feet). The plant grows at a moderate pace, taking 5-10 years to reach its ultimate size according to RHS guidelines. Individual leaves measure 60-200cm long and 4-10cm wide, displaying a distinctive metallic silvery sheen.

Astelia chathamica is endemic to the Chatham Islands, a remote archipelago located approximately 800km southeast of mainland New Zealand. It occurs naturally on both Chatham Island and Pitt Island, where it grows in moist habitats including forest floors, cliffs, rock bluffs, lakeshore scarps, stream margins, and swamps. The silvery foliage helps reflect harsh sunlight and reduce water loss in its exposed coastal habitat.

Astelia chathamica prefers consistently moist but well-drained soil and should not be allowed to dry out completely during the growing season. Water regularly to maintain even moisture, but ensure good drainage as the plant cannot tolerate waterlogging. In its native habitat it grows near streams and in swampy areas, indicating its preference for moisture. Reduce watering slightly in winter but never let the roots completely dry out.

Astelia chathamica thrives in fertile, moist but well-drained soil. It tolerates a range of soil types including clay, loam, and sandy soils, and is adaptable to acidic, neutral, or alkaline pH levels. The key requirement is good drainage combined with moisture retention - rich, humus-rich soil works well.

Astelia chathamica is hardy to approximately -5°C (23°F), classified as RHS H3 hardiness (suitable for coastal and mild UK areas). However, foliage can be damaged by hard frosts and cold, drying winds. In areas with temperatures regularly below -3°C (27°F), provide winter protection such as horticultural fleece or mulching. Container plants should be moved to unheated sheltered areas during severe cold snaps.

Astelia chathamica can be propagated by division or seed. To divide, separate established clumps in spring when new growth begins. For seed propagation, sow fresh seeds in containers placed in a cold frame as soon as they ripen (autumn). Seeds should be sown thinly and shallowly, kept warm (15-21°C) until germination, then cooler. Note that this species is dioecious, so seed propagation ensures a mix of male and female plants needed for berry production.

Astelia chathamica is dioecious, meaning individual plants are either male or female. Male plants produce thick flower stalks with dark green, scented flowers, while female plants bear pale greenish-white blooms that are less showy. Flowering occurs in summer (June-August in the Northern Hemisphere). Female plants that have been pollinated develop attractive orange berries approximately 10mm in diameter from late summer through winter.

Astelia chathamica requires cross-pollination between male and female plants to produce berries, as it is dioecious (separate sexes on different plants). Male flowers are scented to attract insect pollinators. For berry production in gardens, you'll need at least one male and one female plant in proximity. The orange berries that follow successful pollination are then dispersed by birds (frugivory) in the wild.

Astelia chathamica is primarily an outdoor plant, thriving in USDA zones 8-10 and RHS hardiness H3 regions. It performs exceptionally well in coastal gardens and mild climates. Plant in a sheltered spot protected from cold, drying winds, in west, south, or east-facing positions. In colder areas (USDA zone 7 or below), grow in containers that can be moved to protected locations during winter or provide fleece protection when temperatures drop below -5°C.

Astelia chathamica requires minimal pruning. In spring, remove or trim any foliage that has been damaged by winter frost or cold winds. Simply cut away brown or damaged leaves at the base to maintain the plant's appearance and encourage healthy new growth. No regular shaping or cutting back is needed as the plant naturally forms an attractive clump of arching silvery leaves.

Astelia chathamica is generally trouble-free in cultivation, with no significant pest or disease problems reported. The RHS notes it is pest-free and disease-free. The main threat to this species in its native Chatham Islands habitat is browsing by stock and feral animals rather than pathogens. In gardens, ensure good drainage to prevent root rot, which can occur in waterlogged conditions.

Several cultivated varieties of Astelia chathamica are available, with 'Silver Spear' being the most common commercial form. Other cultivars include 'Silver Shadow' and 'Silver Sword', all selected for their striking silvery foliage. These cultivars have received the RHS Award of Garden Merit, recognizing their garden-worthy performance. All share the same basic care requirements as the species.