Argyroxiphium sandwicense subsp. macrocephalum

Haleakalā silversword

Haleakalā silversword is a rare plant found on the Haleakalā volcano, in Haleakalā National Park. Plants grow directly on volcanic cinder where little else grows. Plans to protect these unique plants from extinction were proceeding well until the 1990s, when changes in trade winds subjected them to hotter and dryer conditions.

Plants: A roughly spherical array of sharp, succulent “swords.” The silvery leaves resemble an ethereal pin cushion. (The Hawaiian name for the species, ’āhinahina, means “very gray” or “shining.”) Each plant can live up to 90 years, then flowering once and dying.

Leaves: Leaves have evolved to focus and concentrate sunlight, and their hairs help to retain it, increasing leaf tip temperatures to as much as 68°F (20°C), despite low temperatures at high elevations. Each leaf is 6–16″ (15–40 cm) long, and ⅛–½″ (5–15 mm) wide at the middle.

Flowers: When plants reach approximately 1½′ (50 cm) in diameter, they produce a flowering stalk up to 6½′ (2 m) in height, filled with maroon, pink, or wine-red ray flowers. Each flower stalk may have 11-42 ray flowers, and 50-600 disc florets. They appear between July and October. After flowering and producing seed, the plant dies.

Fruits: Dry and one-seeded, straight or curved like a bow, and ¼–½″ (7–15 mm) long.

Habitats: At elevations above 1.3 mi (2.1 km) on the Haleakalā volcano, in Haleakalā National Park.

Online References:

 

Argyroxiphium sandwicense subsp. macrocephalum description by Thomas H. Kent, not updated.

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