It is endemic to Hawaii where it is the only member of the silversword alliance that is found on all six of the largest islands (Kaua'i, O'ahu, Moloka'i, Lana'i, Maui, Hawai'i).

[3] This plant varies in morphology, taking the form of a small shrub to a tree up to 7 meters tall.

magnifolia is a shrub or a tree which is endemic to Kaua'i, where there are no more than 2 populations remaining.

[6] These plants grow in moist and wet forest habitat with 75 to over 700 centimeters of precipitation annually.

[2] Threats to this species and its habitat include landslides, rockslides, erosion, flooding, and invasive plant species such as hilo grass (Paspalum conjugatum).