About Lyonothamnus floribundus A.Gray
Lyonothamnus floribundus, commonly called island ironwood, is endemic to California's Channel Islands, where it grows in chaparral and oak woodlands of rocky coastal canyons. It is a tree that reaches up to 15 metres (49 ft) tall, with peeling reddish gray or brown bark. Its evergreen leaves are shiny dark green with lighter undersides, and grow on short petioles. The two recognized subspecies have distinct leaf shapes. Its inflorescence is a cluster of woolly white flowers that bear many short, whiskery stamens. The fruit it produces is a pair of hard follicles. In natural island populations, this tree grows in distinct groves. Isozyme analysis has found that each grove is actually a clonal colony. Each clonal genet (genetically identical ironwood clone) consists of 12 to several hundred individual tree trunks called ramets. Later RAPD DNA analysis confirmed that these trees grow in clonal colonies. As this species is clonal, there are far fewer genetically distinct individuals per island. Isolated clones located in the islands' steep rugged terrain have limited opportunities for cross pollination. Limited cross pollination is thought to explain the low seed production and seed viability observed in natural island populations. Protecting the genetic integrity of each island's population of Lyonothamnus floribundus is an important conservation goal. Island resource managers must protect this genetic integrity by prohibiting introductions of Lyonothamnus from other islands or the mainland, including nursery-grown stock. Two documented introductions of L. f. ssp. aspleniifolius to Santa Catalina Island currently threaten the island's native L. f. ssp. floribundus populations. The subspecies Lyonothamnus floribundus ssp. aspleniifolius is cultivated in the horticultural nursery trade. It is used in landscape design for drought-tolerant gardens, California native plant gardens, traditional gardens, and habitat-wildlife gardens, and is planted in both public landscapes and private residential gardens.
