A local cultivar of P. lactiflora called 'bobaishao' planted in Bozhou, China, was used in the present study. The crops were managed according to the integrated cultivation protocols, and the roots were harvested from October 12, 2012, to September 23, 2013, in 12 stages. All the crops were planted during August 19-21, 2009, collected from the same field, and stored in a freezer at -80 ℃ until analysis. Sample list of P. lactiflora roots at various stages during growth: BS1 (October 12, 2012); BS2 (November 12, 2012); BS3 (December 20, 2012); BS4 (January 20, 2013); BS5 (February 20, 2013); BS6 (March 23, 2013); BS7 (April 20, 2013); BS8 (May 25, 2013); BS9 (June 26, 2013); BS10 (July 21, 2013); BS11 (August 20, 2013); BS12 (September 23, 2013).

The total content of monoterpenoid glycosides and phenols peaked in December. For nucleosides and nucleobases, the highest content appeared in April. The maximum phasic accumulation of the total amino acids took place in March, and the content of total polysaccharides reached a peak value in September. December, April, and March were selected as the appropriate harvesting times for producing natural medicinal or health food products. Plant beta-glucosidases and esterases showed the highest activity in December and May, respectively. When the activity of beta-glucosidase increased, esterase activity decreased, while the contents of oxypaeoniflora and paeoniflorin increased. When esterase activity increased, the contents of benzoylpaeoniflorin, paeoniflorin, and gallic acid decreased. In conclusion, the results from the present study would be useful in determination of the suitable time for harvesting P. lactiflora roots for medicinal purposes.