Freely growing tea shoots shows a phasic growth. It grows through alternating state of growth and dormancy. The apex of an elongating tea shoot or the bud unfolds leaves one after another and after making some growth, the growing bud discloses a small bud known as banjhi (sterile) bud. That means the shoot enters in a state of dormancy. The term banjhi has derived from Assamese language and it is widely used in tea scientific writings. The amount of growth made between two states of dormancy is known as a Flush. A tea shoot produces up to four flushes in a season in freely growing plants in N.E.India and Sri Lanka. However, the fifth flush is also seen, though rare, in a few genotypes.
The growth of a flush starts first unfolding two cataphylls or bud scales known in N.E. India as “Janam” or birth scale. (an Assamese word meaning birth).The janams drop off immediately,leaving behind scars on the stem, separated by very short internodes. After that another appendage, called “fish leaf” or “gol pat” (round leaf) is unfolded. The fish leaf is rich green in colour with prominent venation and is often partially serrated and persistent like a normal foliage leaf .After unfolding the fish leaf, normal foliage leaves unfold one after another until the banjhi bud is exposed. The whole process is repeated in due course to produce the next flush. This is what we call phasic growth in tea or growth periodicity.
You may be interested to know why the growing bud becomes banjhi or dormant after producing some growth? Investigators have shown that growth of vascular tissues below the bud cannot keep pace with the rapid elongation of a flushing shoot and consequent reduction of in vascular tissues causes a “bottleneck”. As a result, the apical meristem does not receive adequate supply of water and nutrient to lay down new appendages and the bud comes to a state of apparent rest (banjhi). However, the vascular area below it continues to increase in size. After sometime, when the vascular area enlarges sufficiently, the bud starts getting the required amount of water and nutrients, new initials are formed and in due course the bud starts growing again. This is the cause of banjhiness or flushing and dormancy in tea.
You will come to know later how the different plucking systems have been developed based on the position of the janams and the fish leaf in a growing shoot.
A banjhi bud may not be formed between flushes on every shoot on a tea bush under plucking.Shoots from tea bushes under plucking are plucked or harvested at two to three-leaf stage before they get the chance of completing a flush. However, some shoots become banjhi in the tea bush and the incidence of banjhi formation is more in weak bushes. Normally the vigorous shoots in the central zone of the bush of in vigorous section of tea, formation of banjhi shoots are less. It can be explained that the limitations imposed by reduction of the vascular tissue area below the growing bud could be overcome, at least to a certain extent, by providing the bush with ample supply of water and nutrients under favourable growing conditions. Shoots formed in the central zone of a bush get ample water and nutrients as they are in the direct line of flow of the sap.