Influence of Seeding Date on Flowering and Seed Production of Velvetleaf (Abutilon theophrasti Medic.)

Abstract

In 1993 a field experiment was conducted to determine the influence of seeding date on flowering and seed production of velvetleaf at Kyushu National Agricultural Experiment Station, Nishigoshi, Kumamoto, on thick high humic Andosols (Melanudands). Velvetleaf seeds were seeded monthly from April to November in plots fertilized in advance at 1kg N, 1kg P₂O₅ and 1kg K₂O/a with a compound fertilizer. Flowering and seed production of the emerged plants were evaluated.
Flowering was observed in the April to August seeded plants and mature seed production in the April to July seeded ones. Days from seeding to first flowering, plant height and plant age in leaf number, and days from seeding to initiation of the production of mature capsules were decreased with the later seeding dates, and both flowering and seed production showed short-day photoperiodic response. The number of seeds produced per plant ranged from 2, 214 in the April seeded plants to 424 in the July seeded. Weights of 100 seeds ranged from 866mg in the plants in the May seeding to 993mg in those in the July seeding, and the seeds produced by the plants seeded in April and July were heavier than those seeded in May and August.
Thus, in Kyushu, velvetleaf emerging from April to July was able to efficiently produce vigorous seeds due to the short-day photoperiodic response, and plants emerging in April might cause the most serious problem by producing a large amount of seeds.