Volcanic ashes, fine particles of fragmented volcanic rock and minerals, form into soil in Hawaii, Washington, Oregon, Japan, Indonesia, Central America and other mountainous regions of the world. This fertile soil is ideal for growing plants. Among the plants that grow in volcanic soil are flowers, which produce some of the most exotic and colorful blooms that you will ever find.
Some orchids, specifically mountain orchids, grow in volcanic soils. Noteworthy among these orchids is Pleurothallis truncate, which grows in Pululahua Geobotanical Reserve near the Pululahua volcano in Ecuador. Originating in Ecuador and Colombia, this orchid has spatula-shaped, elongated, dark green leaves. Stalked, bead-like, bright orange flowers arranged singly appear from the leaves each measuring approximately 1/4 inch wide. The flowers bloom twice a year. Preferring part to full shade and moist condition, P. truncate reaches up to 10 inches tall.
Also known as banana passion flower, Passiflora mixta grows near the volcanic mountains of Ecuador and Colombia. It is a climbing vine with trilobed, serrated leaves. Pollinated by hummingbirds, P. mixta produces light pink to bright pink flowers with light green floral tubes and ovate bracts. It produces spindle-shaped fruits, each weighing approximately 1 lb. and featuring soft, yellow-orange pericarp (fruit wall), orange pulp and numerous black seeds.
P. mixta can grow in both high and low light levels; however, seedlings cannot tolerate dense shade. It grows in a mean annual temperature of up to 59 degrees F, but can also tolerate mild or occasional frosts. The vines spreads laterally once they reach canopy height.
The Haleakala ahinahina, or Hawaii silversword, grows on the upper slopes of Haleakala. A low-growing plant with a large taproot that secures it from the strong winds, silversword had adapted well to the harsh volcanic environment. It uses its dense covering of silver hair and its slender leaves, which keep the plant moist and protect it from the severe rays of the sun. The smaller roots are shallow and fibrous and extend out to up to 6 feet to collect water from its surrounding.
The flower stalk grows from 2 to 8 feet tall and produces hundreds of purplish flowers measuring up to 2 inches wide. Upon close inspection, these flowers appear similar to sunflowers. The U.S. Fish and Wildlife Service listed the silversword as an endangered species due to the effects of foraging animals, such as goats and cattle, and visitors pulling the roots of the plants for souvenirs.