Effect of planting density and harvesting date on yield and quality of Artemisia argyi

Background Field investigations revealed that during the production of Artemisia argyi Lévl. et Vant. excessive planting density and untimely harvesting lead to desiccation and abscission of leaves in the middle and lower plant sections. The height of these withered leaves (dead leaf height) accounted for over 50% of the plant height, significantly reducing both the yield and quality of the medicinal herb A. argyi leaves. Methods This study employed field experiments using Nanyang A. argyi as the test material. Agronomic traits (including plant height, canopy width, number of effective leaves on the main stem, dead leaf height, stem diameter, internode length, and yield) and quality indicators (including volatile oil content, moxa yield rate, eucalyptol content, borneol content, and total flavonoid content) were measured under different planting density treatments and at different harvest times. Results The results demonstrated that reducing planting density promoted sturdier plant growth, increased the number of effective leaves on the main stem, decreased the dead leaf height, and increased the dry matter ratio of the A. argyi leaves. As the harvest time was delayed, the number of effective leaves on the main stem, dead leaf height, and yield all gradually increased. The volatile oil content, eucalyptol content, and borneol content in A. argyi leaves increased gradually with decreasing planting density. These same components initially increased and then decreased as the harvest time was extended. Conversely, the combustion calorific value of A. argyi down, total flavonoid content, polysaccharide content, and polyphenol content generally decreased gradually with reduced density. The combustion calorific value, total flavonoid content, and polyphenol content also exhibited an initial increase followed by a decrease with prolonged harvest time. Conclusions Comprehensive analysis of essential oil content, down yield rate, eucalyptol content, borneol content, dry matter ratio, and yield across different densities and harvest periods indicated that for spring-planted A. argyi , a planting spacing of 20 cm × 40 cm combined with harvesting one week after the Dragon Boat Festival resulted in superior overall quality and higher yield.