Life-history monographs of Japanese plants. 9: Helonias orientalis (Thunb.) N. Tanaka (Liliaceae)

The life‐history characteristics of Helonias orientalis (Liliaceae) are described. The genus Helonias (Liliaceae), which includes Heloniopsis and Ypsilandra, is one of the representative members of the so‐called Arcto‐Tertiary Geoflora, with typical disjunct geographical ranges in eastern North America and eastern Asia, including the Japanese Islands to inland China and the Himalayan Mountains. The seasonal growth patterns of this evergreen perennial are most unique, showing different replacement patterns in foliage leaves, which are formed during two different seasons, once in late spring and again in late summer to autumn. Flowering occurs at different times of the year in populations that are located at different elevations. Lowland populations flower in late March to early April, whereas montane and subalpine–alpine populations bear flowers in early to mid‐summer, June to August. Another outstanding feature of this species is that it produces tiny plantlets at the tips of the oldest (3‐year‐old) foliage leaves just before decaying. Survival rates of plantlets (ramets) are obviously much higher than that of the exceedingly minute seedlings (gamets), especially on the dark shady forest floor. Thus, populations in closed woodland habitats are primarily maintained by plantlets, that is, vegetative plantlet formation. The cost of seed production is dramatically higher in the subalpine–alpine populations compared with those of the lowland populations.