A tree showing seasonal activities shows a sigmoid growth curve or S-curve. This growth curve is plotted by Von Sachs on the basis of time and growth pattern of an organism. The recognized growth phases are- lag phase, log phase, steady or stationary phase. The lag phase shows slow growth while the log phase exhibits rapid and maximum growth; hence, termed as the exponential phase. In the stationary phase, the growth slows down or stop to maintain the size and thus also termed as maturation phase.