Broccoli (Brassica oleracea) Yields and Size of Flowering Head as Affected by Planting Distance

Broccoli (Brassica oleracea) produces a large flowering head that is used as a vegetable. It is rich in vitamin C, fiber, and anticancer compounds. Size of broccoli head is an important quality attribute. Broccoli crowns (diameter = 6.4 to 12.8 cm) have a higher market price compared to bunched broccoli. The objective was to determine the impact of planting distance on broccoli yield and size of broccoli flowering head. Broccoli ‘Emerald Crown’ was planted on bare soil on three rows per bed (1.8-m centers) on 7 Nov. 2013. Plants were thinned to the following planting distances within the row: 15, 19, 25, 38 and 76 cm. Plants were harvested on 7 Feb. 2014, when plants had high number of crown florets. Broccoli flowering heads were graded as marketable (crowns or bunched) and culls, according to U.S. grading standards. Above-ground plant biomass increased with increasing planting density. Yield of broccoli crowns increased with planting distance reaching a maximum at 25 cm; there was no augment in yield of crowns with further increments in planting density above 25 cm. Total broccoli yield also increased with increasing planting density reaching a maximum at 25 cm and decreased with further increments in planting density. Weight of individual crowns increased quadratically with increasing planting density. Thus, planting distance had a strong effect on both total marketable yield and broccoli size of both crowns and bunched broccoli.