Assessment of heading performance and inflorescence visibility in Miscanthus sinensis cultivars

Miscanthus sinensis (Poaceae) cultivars have great values as ornamental grasses and adapt well to various environmental conditions. To assess the inflorescence visibility of seven popular Miscanthus cultivars (‘Gold Breeze’, ‘Strictus’, ‘Morning Light’, ‘Variegatus’, ‘Gracillimus’, ‘Kleine Fontäne’, and ‘Common’), the heading performance and morphological characteristics were analyzed. The test cultivars were transplanted and cultivated on research plots in 2013 and data were collected from July 2017 to February 2018. Among the six cultivars, except ‘Gold Breeze’, which had not bloomed during the research period, ‘Kleine Fontäne’ showed the longest heading period and the highest peduncle density. Heading patterns were classified in the early and the late heading patterns. The early heading pattern cultivars (‘Kleine Fontäne’, ‘Common’, and ‘Strictus’) had a high weekly heading rate (WHR), and reached later heading peak time with low mean heading rate (MHR). However, the late heading pattern cultivars (‘Variegatus’, ‘Gracillimus’, and ‘Morning Light’) had high WHR at the beginning of the heading initiation and reached earlier heading peak time with high MHR. The changes of inflorescence stage were classified into the flowering season (stage 1), the seed maturation (stage 2), and the seed shatter stages (stage 3). The inflorescence colors were expressed with a reddish (‘Strictus’, ‘Morning Light’, ‘Variegatus’, ‘Gracillimus’, and ‘Common’) and a yellow-greenish (‘Kleine Fontäne’) color in stage 1. The color difference value (ΔE*ab) was greater at stage 1 and stage 2; however, ΔE*ab was decreased in stage 3 compared with the reference inflorescence color of ‘Common’. The morphological characteristics of inflorescences were significantly different among the cultivars, such as the plant height, stem length, dissociation index, length, width, length/width ratio, raceme density, and spikelet density. On the assessment of inflorescence visibility, the morphological characteristics showed a decisive component in ‘Common’, ‘Strictus’, ‘Variegatus’, and ‘Gracillimus’; on the other hand, the heading characteristics were more influential on visibility in ‘Kleine Fontäne’ and ‘Morning Light’. These results suggest that the inflorescence visibility of Miscanthus cultivars was determined by various factors of the heading and morphological characteristics of inflorescence.