Argyroxiphium sandwicense DC.
Hawai'i Silversword, Hawaiian Silversword
Argyroxiphium sandwicense var. sandwicense, Argyroxiphium sandwicense subsp. sandwicense
Argyroxiphium sandwicense is a low-growing plant that forms a rosette of numerous narrow, pointed, silver-green leaves. The rosette grows up to 2 feet (60 cm) in diameter. Clusters of profuse red-purple flowers appear on a up to 10 feet (3 m) tall stem. The plant blooms only once in its life of 20 to 90 years.
USDA hardiness zone 10a to 10b: from 30 °F (−1.1 °C) to 40 °F (+4.4 °C).
How to Grow and Care
The silversword alliance is about 50 species of plants belonging to three genera endemic to the Hawaiian islands. They get their common name from the visually impressive silversword.
These plants only flower once in their lifetime. The silver rosettes grow for a number of years before the inflorescence ascends skywards. Flowers appear from mid-June to November, and after the seeds have been shed, the whole plant dies. These exotic-looking plants are ideally suited to their harsh environment. The silver leaves reflect the sun's rays while their shape prevents moisture loss and protects the more delicate center of the plant from predation.
These attractive plants were previously collected as curiosities. Climbers on the mountains would dig them up as proof that they had reached the summit. Populations were further depleted by browsing and trampling by goats and cattle in the area. Today Argyroxiphium sandwicense is restricted to a single population of as few as 30 plants in the Wailuku River basin on Mauna Kea in Hawaii. These plants are at risk from the small size and range of their population, which is vulnerable to any chance event that might occur.
The Hawai'i Silversword is protected in Hawaii.
It is endemic to Hawaii (found on the mountain Mauna Kea on the Big Island at elevations above 2,600 meters).
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