Figure 6.1 The morphological characteristics of ginger plant. 1. Leaves. 2. Overground stem.
Stem: The stem of ginger has two parts: the overground leafy shoot, or pseudostem, and the underground perennial stem (rhizome). The leafy shoot is erect, green, and formed by enveloping, overlapping leaf sheaths. It is 60 to 100 cm high. Under normal conditions, the aerial shoots increase in height by 1 to 1.2 cm a day; later by the middle of September, the plant height tends to become stable.
In the seedling stage, only vegetative growth takes place, usually one tiller grows out in every 20 days. When entering the root-growing stage, lateral branches of the rhizome grow out quickly; one branch usually grows out every 5 to 6 days. After the middle of October, with the decrease in temperature, the growth slows down. The number of lateral branches (fingers) of the rhizome depends on the cultivars and planting condition. Generally, dense seedling cultivars have 15 to 20 primary fingers under moderate fertility and normal water-supplying conditions, whereas sparse seedling ones have 10 to 15. Cultivars when planted in fertile soil, with adequate supply of water and fertilizers, will have more fingers. There are nodes on the rhizome; the number and the density of the nodes vary in the mother rhizome, and the primary and secondary fingers. Usually, the "mother ginger" is smaller, with short internodes, whereas the primaries are bigger with long internodes.
After planting, the apical bud comes out and becomes the main tiller or primary shoot. Along with the growth of the tiller, its base part inflates gradually into a rhizome. It is the first formed rhizome ball, and is called the mother ginger or the mother rhizome. The buds on both sides of the mother ginger develop and produce two to four tillers and they become the first branches. The bases of these tillers inflate into rhizomes, which become the primary fingers. The buds on these primaries shoot out again and form the second-order tillers, the bases of which develop into secondary fingers. The buds of these branches can shoot out and form the third- and fourth-order tillers and their bases also inflate into the third and fourth-order fingers. The later produced buds usually do not develop into branches due to the increasing cold. Thus, all the rhizome balls formed by
one rhizome are in regular order, which finally give rise to a complete rhizome (Figure 6.2). The newly harvested ginger rhizome is yellow; it is called popularly "tender ginger" or "fresh ginger." After storage, the residual stems and roots fall off. The skin of the rhizome turns to a khaki color and is called "yellow ginger." When the yellow ginger is planted as seed and dug out later in the harvest season, it is called "old ginger."
Leaf: Ginger has green, narrow leaves that are 18 to 24 cm long and 2 to 3 cm wide with short petioles. The leaf sheaths that form the pseudostem are long and narrow. They have the functions of supporting leaves and protecting overground stems. On the junction of leaves and sheathes are a pair of projecting appendages that are the ligules. The newly born leaves are small and rolled into a cylinder, which spread out while growing. The leaves are arranged in a biseriate manner (distichously).
In the seedling stage, the leaf grows slowly; usually 2 to 4 days are needed for a new leaf to come out. With the beginning of autumn the growth quickens, and the leaf area enlarges rapidly. In the rapid-growing stage leaves are produced in quick succession and two leaves are produced every day per plant. After October, with the temperature decreasing, the plant growth slows down, and so also does the leaf growing speed. The leaf area in the seedling stage makes up only 15 to 20 percent of the total leaf area, whereas the leaf area produced from August to October is about 75 percent of the total leaf area (Table 6.1)
Ginger is a vegetatively propagated plant, and in most years, the whole growing period is utilized for vegetative growth only; except in certain years, when some plants produce flowers. So there are no definite growing and flowering phases. Under proper growth conditions, ginger can germinate at any time because it has no natural dormancy. The duration of its growing period is influenced by moisture availability, temperature, and other environmental conditions. The entire growing period can be divided into germinating stage, seedling stage, flourishing growing stage, and dormant stage according to its growing tendency and season (Figure 6.3).
Table 6.1 Growth character of ginger leaves*
Table 6.1 Growth character of ginger leaves*
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