Argyroxiphium sandwicense

Common Names

Hawaii Silversword, Mauna Kea Silversword, Haleakala Silversword, Hawai'i Silversword, Hawaiian Silversword, Ahinahina, Silversword, Hinahina

Summary

The Hawaiʻi silversword comprises two subspecies endemic to Hawaii, occurring on Maui’s Haleakalā and Hawaii Island’s Mauna Kea in dry alpine desert habitats at elevations roughly 2,600–3,800 m. It forms a large ball-shaped basal rosette of narrow daggerlike leaves coated in silvery hairs; leaves reach up to about 40 cm long and 0.3–1.3 cm wide, with clumps forming dense crowns up to about 150 cm across. It is monocarpic, living many years before a single flowering stalk up to about 3 m tall emerges, bearing flower heads about 2 cm in diameter with white–pink ray florets and pink–maroon disk florets; the inflorescence and subtending bracts are covered with sticky glandular hairs that emit a faint sweet odor, and leaves store water as gel.

In cultivation, it requires full sun with direct bright light, moderate temperatures, low humidity, and very dry sandy, well-draining, nutrient-poor soil with minimal watering, and is unsuitable for containers; propagation is challenging and reproduction occurs by seed after flowering. The species is endangered with conservation actions including fencing of habitat, habitat and invasive species management, and propagation/outplanting programs to support remaining populations, which face threats from introduced grazing mammals and reduced pollinator activity due to invasive ants and other disturbances.

Lifecycle

Perennial

Height

2 inches-9 feet 10 inches

Spread

2-2.5 feet

Hardiness Zones

Zones 10a-10b

Sunlight Requirements

Ideally full sun.

Soil Type

Dry, well-draining volcanic/cinder soil with low nutrient availability.

Soil Drainage

Well-drained sandy soil

Soil pH

6.5

Bloom Color

Pink to maroon; occasionally white.

Bloom Time

Summer

Foliage Color

Silvery

Fall Foliage Color

Silvery-green

Leaf Lifecycle

Evergreen broadleaf

Growth Rate

Negative growth; population declined 12–22% (2007–2009)

Seasons of Interest

Summer and Fall

Propagation Methods

Seeds and Division (offsets)

Attracts Wildlife

Attracts other pollinators