THE NATURE OF FLOWERING AND SEED MATURATION OF ONIONS AS A BASIS FOR MECHANICAL HARVESTING OF THE SEEDS
The number of flowers per umbel covered a wide range (200–1000) and was found to depend on cultivar, date of planting, size of bulbs, and growth conditions.
Within an umbel, 25–31 days elapsed from the beginning on the opening of the first flower to that of the last one. In the field, there was a time lag of 20–30 days between umbels in the beginning of flowering. These variations depend mainly on the temperature at flowering time.
Seeds from individual marked flowers which were collected 45–50 days after anthesis were able to germinate; they contained 50–60% dry matter. Younger seeds gave poor germination.
The best time to harvest onion seeds mechanically is at 60–70% dry matter content, which occurs 45–60 days after the beginning of flowering in the field. Another criterion for harvesting should be when 1–3% of the umbels in the field have mature seeds, i.e., when the capsules are open and black seeds are visible. We found that this occured usually 10–12 days before the traditional hand-harvesting of the umbels.