Ginger Root as Rhizome
The ginger root you see in the grocery store is a rhizome, which is an underground stem that some plants use to reproduce. As rhizomes grow beneath the ground, at intervals they produce roots and shoots that can become new plants. When a ginger root has eyes, it is already budding---the eyes are the buds that will grow into a new plant.
Rooting in Water
Ginger can grow in a few ways, because it is an adaptable, easy to grow plant. First, when partially submerged in water (such as hanging by toothpicks in a glass) a ginger root will produce roots. When roots are established, a rhizome placed in soil will grow. However, ginger root grown this way will then need to get used to the soil.
Rooting in Soil
Rhizomes can, instead, be planted directly in soil, living as a potted plant. Laid in a pot of moist, rich, warm soil with about 1 inch of soil on top, a rhizome sitting in the sun will sprout. After that, ginger likes filtered light. Ginger also takes to transplanting in an outdoor garden, so people in cool climates can start ginger indoors at the end of winter. Spring is the time to plant it. Ginger should be planted with the buds face up, 6 to 8 inches apart.
Besides dappled light, ginger needs a sheltered spot where it won't be subjected to strong winds. It needs regular watering, the soil being not too dry and not too soggy. Mulching prevents the soil from drying out. Ginger likes humidity---it's a tropical plant---so a plant grown in dry air needs misting. Gardeners in cold climates are better off growing ginger outside in pots or tubs, then bringing the containers indoors for the winter.
Ginger grows up to 4 feet tall but is slow growing. Leaves are smooth and glossy, are scented and grow long. Meanwhile, the rhizomes are busy beneath the ground. After plants have grown for about four months, small pieces of the rhizomes can be harvested conservatively by digging next to the plant, but these young pieces won't be the most flavorful.
As fall approaches, the above-ground foliage begins to die, which lets the plant put its energy into rhizome growth. At this point, in its natural habitat, the dry season would be coming, so gardeners growing ginger can cut back on water. The foliage will die back and then the ginger rhizomes can be harvested. People growing ginger in pots can bring the plants inside for the winter, still allowing the plant's foliage to die back.
Harvest by digging up the plant for its rhizomes, keeping some for culinary use, while replanting rhizomes with healthy eyes. These will produce new plants in the spring. Ginger shouldn't be harvested aggressively for at least two growing seasons so that it can become well established. If not harvested, the ginger will flower after a couple of years, but unlike ornamental ginger, culinary ginger's flowers aren't pretty.