Lateral Shoot Development Response to Multi-pinching in the Garland Chrysanthemum Cultivar ‘Stick-syungiku’

Garland chrysanthemums are conventionally ratooned and harvested by selective handpicking. Subsequently, the lateral shoots regrow, allowing for further harvests. We previously studied a new ratooning practice for garland chrysanthemums harvested by horizontal cutting, and reported the optimal plant height and cutting height. New shoot development is important for garland chrysanthemum ratooning. However, lateral shoot emergence characteristics of each node have not yet been studied. To address this issue, we investigated lateral shoot development in the garland chrysanthemum cultivar ‘Stick-syungiku’. Each garland chrysanthemum was pinched twice, leaving different numbers of nodes. After each pinching, shoot emergence was evaluated at each nodal section. The emergence rate of new shoots in the entire plant was higher after the first pinching than after the second pinching. Lateral shoot emergence depended on node position. At the first lateral shoot emergence after the first pinching, the emergence rates from the first and second nodes of the main stem were higher than those from the upper nodes. At second lateral shoot development, the emergence rate of shoots from the first lateral shoot that developed from the first and second nodes of the main stem was higher than that of shoots from the first lateral shoot, which developed from the third to sixth nodes of the main stem. Among the first lateral shoots that developed from the third to sixth nodes of the main stem, the second lateral shoot emergence rates from the third and fourth nodes of the first lateral shoot were higher, and the rates from the first and second nodes were lower. These results indicate that lateral shoots originating in the first or second nodes of the main stem should be retained to promote regeneration. In addition, because regrowth from the lower node of the first lateral shoot developed from the upper nodes of the main stem may be weak, the upper node of the first lateral shoot should be retained.