Maria del Pilar Paz and Jeff S. Kuehny
Ornamental gingers encompass a diverse and versatile group of plants that are gaining increased popularity in the flowering pot plant, landscape and cut flower markets. They have showy and attractive foliage and flowers, which make them interesting ornamentals. The various sizes, flower colors and longevity (up to four weeks or longer) are adding needed diversity to the greenhouse industry.
Ornamental gingers are most commonly propagated by rhizomes – underground storage organs that serve as a major source of water and carbohydrates. Each rhizome has many lateral buds, which grow out above ground. In general, the outdoor growing period in Louisiana is seven to eight months, and flowering takes place for two to three months. Flowering initiates new rhizome formation.
A majority of these gingers are native to Southeast Asia, with production occurring predominantly in Thailand and China. In their native habitat, most gingers grow during the rainy season and go dormant during the dry season. If rhizomes are kept dry, they will remain dormant. In con-trast to their native habitat, rhizomes in temperate cli-mates enter dormancy in winter in response to short days and low temperatures. Rhizomes in commercial production are harvested when dormant for storage and distri-bution. Postharvest handling of the rhizomes can have a significant effect on time to emergence and uniformity of emergence.
One of the most popular gingers is the cucuma, which originates in northern Thailand and Cambodia. Curcumas comprise at least 65 species with different colors, forms and sizes. The inflorescence – or flower – is a compressed spike with colorful bracts that can develop from the shoot or directly from the rhizome.
For production of brightly colored bracts and deep green leaves, Curcuma alismatifolia and other species Curcuma should be grown in full sun. Curcuma cordata should be grown in 30 percent to 50 percent shade.
Globba, another popular ginger, have a pseudostem 20 to 30 centimeters tall, terminating with a pendent inflorescence of lavender, pink, white or yellow bracts accented by a slender, curved, yellow petal. Most Globba species grow best and flower under 30 to 50 percent shade.
The 50 species of the genus Kaempferia and the one species of Cornukaempferia are nearly stemless herbs with thick, aromatic rhizomes. They are grown primarily for their beautiful foliage. Most Kaempferia have a silver to purple feather pattern in the middle of the upper side of the leaf radiating outwards with various shades of green. Most of the Kaempferia species produce small white, pink or orange flowers. Each day a solitary flower emerges on a spike arising from the base of the plant and is replaced by another the following day. These gingers grow best under 30 to 50 percent shade. Kaempferia rotunda has proven to be one of the best Kaempferia for landscape planting. The plant has rounded leaves that grow close to the ground, producing a dense mound. Because the foliage of Kaempferia is its primary attribute, transplants from tissue culture will produce a nice pot plant.
Temperature is the primary factor affecting gingers’ sprouting and growth and is commonly used to hasten or delay development. For a species to be used as a potted plant, it must be possible for growers to provide flowering plants within a specific time interval. Because gingers go dormant in the winter, they are suitable for growing as summer flowering potted plants and landscape plants anywhere in the United States. Most rhizomes are harvested from November to January in Thailand and shipped to the United States in February through April. Because gingers prefer warm growing conditions, they are good candidates for summer greenhouse or nursery production, fitting the lull between summer and fall.
All of the aforementioned gingers have been planted in the landscape at Burden Center in Baton Rouge. Over-wintering survival also is linked to good mulching and to well-drained soil to prevent root rot. Thus, these plants can be marketed as a flowering potted plant year-round and as perennials in the landscape. The flower stems of all these gingers also make good cut flowers.
Maria del Pilar Paz and Jeff S. Kuehny, Associate Professor, School of Plant, Environmental and Soil Sciences, LSU AgCenter, Baton Rouge, La.
(This article appeared in the spring 2005 edition of Louisiana Agriculture.)