Ginger is a name casually assigned to many tropical herbs with fragrant, fleshy rhizome roots that are members of the plant family Zingiberaceae. These rhizomes are often harvested and used as culinary spices, flavorings or medicines. Some species display colorful, ornate flowers that are long-lasting and used in cut flower arrangements. These plants are not frost-tolerant, but the underground roots survive and resprout in spring's warmth. Dependent on species, ginger plants are grown in USDA hardiness zones 8 and higher.
Thousands of plants belong to the ginger family, Zingiberaceae, but a few species have particular fame. The spice ginger (Zingiber officinale) and galangal (Alpinia galanga) are two examples of culinary gingers--two cousins that botanically are gingers but are known by different names include turmeric (Curcuma longa), East Indian arrowroot (Curcuma angustifolia) and cardamom (Elettaria cardamomum). Other gingers are regarded for their ornamental flowers or foliage and are planted in tropical gardens--including pinstripe ginger (Alpinia formosana), red ginger (Alpinia purpurata), shell ginger (Alpinia zerumbet), spiral ginger (Costus barbatus), crape ginger (Costus speciosus), butterfly ginger (Hedychium coronarium) and torch ginger (Etlingera elatior).
The vast majority of plants referred to as gingers hails from tropical areas of southern Asia--like India and China, as well as Southeast Asia, including Indonesia. Gingers belonging to the botanical group Costus are native to tropical Central and South America and the West Indies.
All ginger plants grow from a firm, fleshy underground storage stem called a rhizome. Each year new growth shoots emerge from the rhizome and produce leafy stems and flowers. The stems are actually overlapping leaf bases and never become woody like those of shrubs. The leaves are long and paddle-shaped and are arranged alternately on the stems. The flowers are tiny with six petals and housed in waxy, colorful bracts in spike- or cone-like clusters. The seeds produced are called capsules and are either dry or fleshy, according to "Tropical Flowering Plants." Crush any part of a ginger plant and you can smell a sweet but spicy aroma. Those gingers in the genus Costus do not have this scent and this is a reason some taxonomists place them in a separate plant family, Costaceae.
Ginger plants are native to tropical regions free from frost and often have year-round growing seasons. Thus, some plant species are evergreen. More often ginger plants are seasonally dormant, dying back to their rhizomes underground when soil becomes dry, such as during the tropical winter or dry season. The underground roots allow many gingers to grow outdoors in regions with frosty but mild winters as they do not freeze in the soil and simply regrow their stems and leaves in spring.
Grow ginger plants in a moist, well-draining soil that is rich in organic matter like compost, manure or leaf mold. Nonalkaline soils (pH less than 7.8) are best. When temperatures are above 70 degrees F, water and provide liquid fertilizers freely to encourage lush leaf growth and eventual flowering, but when temperatures remain cooler, reduce watering and do not fertilize. Some species produce their flowers among the leaves and stems, and are difficult to see and enjoy.