Argyroxiphium sandwicense aka Silversword

Argyroxiphium sandwicense is a silversword from the Hawaiian Islands. It belongs to Asteraceae, the daisy family. Its common names include Hawaii silversword and Mauna Kea silversword. The Hawaiian name is ʻAhinahina. This woody plant forms a dense rosette near ground level. Most plants have one stem, though some develop branches. The crown can form a rounded mound or cone.

Long, narrow leaves give the crown its silver look. Dense silver hairs cover their whole surface. The fleshy blades taper like swords and have smooth edges. Sources give leaf lengths of about 10–12 inches [0.25–0.30 metres]. The leaves grow in a spiral around the stem. They can store water as gel within their tissues. The short, thin trunk reaches about 0.16–0.26 feet [0.05–0.08 metres]. Old leaves stay attached after they dry. These leaves hide the bark and help shield the stem from frost.

The leafy rosette can span about 2 feet [0.60 metres] or more. LLIFLE gives flowering plants a width of 2.5 feet [0.75 metres]. Virginia Tech describes a flower stalk reaching 6 feet [1.83 metres]. LLIFLE reports flowering plants reaching nearly 10 feet [3 metres]. These figures describe the tall flowering stage, not just the rosette. Plants may live for 5–50 years before they bloom. Most then die after their single flowering event. Branched plants can flower over several years. Each rosette dies after flowering, while other rosettes may remain alive.

Flowers appear from June to November on a tall central stalk. Hundreds of flower heads crowd its short branches. LLIFLE reports as many as 800 heads on one stalk. Each head measures about an inch [0.02–0.025 metres] across. Small disk florets fill the centre of each head. Around a dozen ray flowers line the edge. Flower colours include pink, maroon, and purple-brown. Ray flowers can also be white. Sticky glandular hairs cover parts of the flowering stalk. They give off a faint sweet scent.

The plant relies on insects to transfer pollen. It cannot fertilise itself. Each floret can form a slender, black achene. These fruits reach about 0.03 feet [0.01 metres] long. A fruit may contain one seed or none. Small, uneven scales form a pappus at its tip.