New Zealand flax (Phormium tenax) HPWRA Score: 8 High Risk
Impacts: This self-compatible flax produces abundant viable seeds (10,000 per plant) that are wind dispersed and shade tolerant. This rosette-like lily forms dense thickets from which other species are excluded. It crowds out native vegetation and blocks the sunlight. Plants can root on the ground, in hapu’u trunks, open pig disturbed grassland, and along steep ridges. It can invade a relatively intact native forest and as well as disturbed grassland. Listed as one of the top ten priority species by The Nature Conservancy for eradication, a large infestation has established in the Montane Ohia-Uluhe rainforest of Kamakou Preserve at approximately 3750 ft in Molokai’i. The main population, which is located just above Pu’u Kolekole, thrives in a very wet flat area with poor drainage.
Description: An evergreen, perennial monocot that can grow up to 13′ tall and 7′ wide. Flowers are red or yellow tubular flowers that arise in bunches extending up to 12′ tall. The leaves are rigid, sword-shaped and erect. Leaf color can range from bright green to bronze and purple. The fruit is a 3-angled capsule up to 4″ long, containing many small wind-dispersed seeds.
Comments from green industry professionals: “Dense thickets in no time”, “beautiful but invasive”, “Very tough to remove from landscape once established”, “Nice plant but there are many substitutions that aren’t invasive”, “You need a bulldozer to get it off your property”, “the roots go to hell and back”