Development of Two Heads Harvesting Methods for Broccoli (Brassica Oleracea L. var. Italica)

Abstract

Broccoli (Brassica oleracea L. var. italica) production and consumption have rapidly increased in Japan, and it is expected to be recognized as a “designated vegetable” by 2026. However, approximately 30% of domestic broccoli for consumption is imported, which means that there is a pressing need to increase domestic production. In Japan, broccoli heads that are harvested and shipped to the market are primarily from the apical bud, with only one head per plant. If the lateral heads from lateral branches (axillary buds) could grow to a marketable size, broccoli production would significantly increase. This study aimed to develop cultivation methods that enable harvesting two heads per plant using lateral branches. By selecting cultivars, investigating the probability of axillary bud generation at each node, and determining the proper timing for decapitation, two cultivation methods were established: “L-shaping” and “V-shaping”. L-shaping is a method that enables the harvest of 10 cm diameter lateral heads after the harvest of a 12 cm diameter apical head in April and May by limiting the number of lateral branches to one or two. This method increased the number of 10 cm heads by approximately 80%, with total yields reaching 17,000 kg per ha. V-shaping enables the harvesting of two 12 cm diameter heads during autumn cropping by pinching the apical bud and limiting the number of lateral branches to two. Pinching at the 7^th to 11^th leaf stage increased the number of 12 cm heads by approximately 60%, with yields reaching 13,000 kg per ha. Both methods exceeded the national average yield of 10,000 kg per ha, making them highly promising for increasing fresh broccoli production in Japan.