Regeneration of the Mauna Kea silversword Argyroxiphium sandwicense (Asteraceae) in Hawaii Original Research Article

The Mauna Kea silversword Argyroxiphium sandwicense is an endangered plant endemic to the high elevation cinder deserts of Mauna Kea on the Island of Hawaii. Restoration efforts have increased the total naturally occurring population of ca. 50 adult plants by ca. 500 individuals, primarily by the outplanting of silverswords initially grown under controlled conditions. We evaluated the direct sowing of seeds into field sites as an alternative to outplanting. Gravel-covered surfaces enhanced germination and growth of seedlings and increased soil moisture. The presence of shrubs and trees was associated with increased silversword germination but decreased silversword growth and reproduction. The best environment for silverswords varied throughout the life cycle of the plant, but critical stages are pollination, seed production, germination, and seedling survival. Sowing and outplanting each have unique advantages. High elevation, moist, gravel surfaces that can be protected from ungulate browsing should be the focus of future sowing and outplanting efforts to maximize restoration success.