HPWRA Score: 14 High Risk
Impacts: Spreads rapidly in mesic to wet areas, invading pastures and mature forests. The prolific seeds germinate quickly, reaching reproductive age in a few years. The dense thickets can crowd native vegetation in forests and waterways. The tree grows up to 6 feet a year, is shade tolerant and resprouts after cutting. The seeds are numerous, wind-dispersed, can contaminate other potted plants and they can float on water. There are major infestations tucked away in almost every rainforest valley along the northern and eastern slopes of Kaua’i, O’ahu, Hawai’i, and East Maui. Both the yellow and the red-flowered trees are considered one of the major threats for Hibiscus brackenridgei ssp. mokuleianus.
Toxic to some pollinators, research indicates this ever-blooming tree is a constant threat to beneficial insects. Deadly nectar pools inside the numerous cup-shaped flowers. Unsuspecting pollinators face a quick death after imbibing the deadly substance. Unable to fly away they drown inside the insect-killing flower.
Description: Native to Africa, this ornamental tree was planted widely throughout the state and is now invading many mesic to wet areas. It is thought that Hillebrand first introduced the tree to Hawai’i, with later re-introductions by Joseph Rock. The Division of Forestry and Wildlife of the Hawai`i Department of Land and Natural Resources has designated this species as one of Hawai`i’s Most Invasive Horticultural Plants. The flowers are scarlet to orange to yellow, showy flowers, grow in clusters (about 4 in high and 8 in across) and bloom year-round. The leaves are oddly-pinnately compound leaflets. Fruit clusters are upright in canoe-shaped seed capsules up to 10 inches long. The capsules dehisce in an explosion of seeds that are wind-dispersed.