【Background】Tiller and rhizome productions are the main modes of Spartina alterniflora propagation. Few however have studied the rates of propagation of underground rhizomes and the links between tiller and rhizome production over time.【Method】The monthly production of tiller and rhizome, in terms of biomass, was measured on transplants of S.alterniflorain the town of Feiluan, Ningde City.【Result】There were two peaks of tiller productionin this area. The first peak was from May to June. During this period, rhizomes grew slowly. The highest ratio of tiller to rhizome biomass was at the end of June. These results indicated that the growth of S.alterniflora was mainly through tiller production during this period. The second apparent peak was in September and October. The increase of small tillers was higher in September～October than in May～June but the tiller absolute growth rate (AGR) was lower. The growth of the small tillers after September might be restricted. AGR of tiller slowed down in August, while the total number of rhizomes and rhizome AGR increased, reaching a maximum in August～September. From September to December, AGR of tillers and rhizomes continued to decrease.These results indicate that S.alterniflora allocate growth to accumulation and extension of underground rhizome from August on.【Conclusion and significance】The study shows that S.alterniflora mainly develops tillers before July and rhizomes after July in Ningde area, which provides a theoretical reference for control of S.alterniflora.