Authors: Tim Tunison, Global Invasive Species Team, The Nature Conservancy
Latin Name: Hedychium coronarium
Common Name: white ginger
Erect, coarse herbaceous perennial, 1-2 m tall.
Hedychium coronarium is considered a pest by Smith (1985) only on Maui and Hawaii.
Hedychium coronarium is capable of forming dense, single species stands by vegetative spread through the expansion of a dense rhizome. The importance of spread from seed may be minimal except at lower elevations. White ginger is one of the most disruptive alien plant species at Kamakou Preserve, particularly in drainages in mesic sites where rare plants tend to be concentrated. Control away from drainages can be carried out by herbicides, Escort being the most likely candidate. Control in the drainages should probably be mechanical/manual unless a non-mobile herbicide can be identified. Recovery in white ginger sites and production of viable seed at Kamakou should be monitored, if time permits.
Probably native to the Himalayas and southeastern China, and now naturalized in mesic (Wagner et al. 1990) and wet forest in Hawaii (Smith 1985). It is found on the five largest islands.
Naturalized in mesic (Wagner et al. 1990) and wet forest in Hawaii (Smith 1985).
The ecology of Hedychium coronarium has been little studied. It appears to be relatively shade tolerant, as indicated by its growth in partial shade at Kamakou Preserve. It is capable of growing in exposed sites. Seed is produced at lower elevations in Hawaii, but have lower dispersal potential because seeds are not displayed for avian vectors (Smith pers. comm. 1985). Seed is not produced on Hawaii Island at 1,200 m elevation (Cuddihy pers. comm., Hawaii Volcanoes National Park, 1991). White ginger does not produce seeds at Kalopa State Park at 600 m (Tomich pers. comm., State of Hawaii, 1991 ). Exact elevation limits to seed production are not known. White ginger distribution at Kamakou Preserve can be explained by dispersal of rhizome fragments by water or road maintenance machinery. Dense colonies arise vegetatively by spread of the rhizomes.
Smith (1985) ranks Hedychium coronarium as one of the 86 most disruptive alien plants in Hawaii because of its capacity to form extensive single species stands. It is considered a pest by Smith (1985) only on Maui and Hawaii. However, white ginger is also disruptively invasive on Molokai at Kamakou Preserve. It is not found at Waikamoi Preserve.
Hedychium coronarium should be controlled at Kamakou, especially in drainages because of a threat to rare mesic shrubland flora in these sites.
Kamakou staff has effectively controlled some Hedychium coronarium populations by a combination of manual and mechanical means. These labor-intensive methods are effective on invasive ginger species in Hawaii. Often considerable follow-up is needed because of the difficulty of locating and removing all rhizome fragments, which are capable of resprouting.
A mechanical method that has been effective on kahili ginger and would probably work on white ginger is repreated mowings. The shoots are cut off with a weed eater. Resprouting shoots are cut when they reach 12 inches. Ninety percent control is achieved with kahili ginger in approximately one year, although complete control may require several years (Markowitz pers. comm.).
Escort®, at a concentration of 4.5 g/l of water, without a surfactant, is highly effective on kahili ginger (Hedychium gardnerianum) (Cuddihy pers. comm.(b)). This was also relatively effective on an unreplicated trial on white ginger at Hawaii Volcanoes.
Tomich (pers. comm.) found that undiluted Roundup® was effective on white ginger when applied to the above ground roots emerging from the rhizomes, after the shoots were removed. However, local State Department of Agriculture officials should be consulted before using this method, which may be interpreted as a foliar application rather than a cut-surface application.
Hedychium coronarium has been controlled at Kalopa State Park (Tomich pers. comm.). Kamakou has successfully controlled some white ginger colonies.
Recovery of sites where Hedychium coronarium has been removed by manual/mechanical or herbicidal means should be monitored at Kamakou Preserve. The production of viable seed or presence of seedling recruitment should also be monitored at Kamakou.
Standard plot counts and cover changes; observation of seed production and germination tests.
Management Research Programs:
Arakaki is studying the effectiveness of Escort in Hedychium coronarium control at Kamakou Preserve (Misaki pers. comm.)
Management Research Needs:
Identification of an effective non-mobile herbicide would be useful in control of Hedychium coronarium at Kamakou. Detailed studies of life-history and ecology, useful for state-wide control of widespread species such as clidemia (Clidemia hirta) are not needed for a localized threat such as white ginger.