Clonal plant rhizomes not only function in vegetative propagation and population expansion, but also act as a physiological channel, integrating buds and ramets. Examining the rhizome components can reveal information regarding the birth, death, and age of the plants, and the seasonal dynamics of rhizomes at different ages can reflect survival and senescence processes. A field investigation was carried out on the rhizomes of Phragmites australis populations in different habitats of the Zhalong Wetland. Soil from a unit area was sampled to assess the seasonal dynamics of rhizome length, biomass, and dry matter storage at different ages. The results showed that rhizome length, biomass, and dry matter storage of 1st increased exponentially from July to October and that there was a long period of growth and material accumulation in the middle and late growing period. From June to October, the rhizome lengths of 2nd and 3rd increased linearly, and the rhizome length of 4th to 6th decreased linearly. The rhizome biomass of 2nd to 4th and the dry matter storage of 2nd to 5th decreased initially and then increased quadratically. The rhizome biomass of 5th or 6th and the dry matter storage of 6th decreased with the power function. During the entire growing period, the rhizome length and biomass of 3rd were the highest and the rhizome length of the 6th were the lowest and the biomass of the 1st the lowest; The dry matter storage of 5th was the highest and that of 1st was the lowest. There was a relatively stable difference and differential sequence between age classes in rhizome length, biomass, and dry matter storage of P. australis populations in the four different habitats. The emergence of new rhizomes, survival of old rhizomes, lifetime of rhizomes, and nutrient consumption and storage showed relatively stable biological characteristics. The status and function of rhizomes and their contribution to the population varied in different age classes.