Flowering Habit of Delphinium grandiflorum L. in the Cool Northern Areas of Japan

Abstract

To clarify the flowering habit of Delphinium grandiflorum L. in the cool northern areas of Japan, the relationship between the developmental stage of flower bud and the expression of bolting was examined. Plants were sown in late May and began to form flower buds two weeks prior to bolting at the beginning of August. They flowered three weeks after the start of bolting. When plants were sown between July and September, the days to bolting increased markedly. However, in plants sown between the end of March and June, early bolting occurred and the days to bolting decreased. Among plants sown between July and August, two groups were observed with different numbers of days to bolting. Positive correlation was observed between the days to bolting and the days to flowering.